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Applied Catalysis B, Environmental (v.110, #)

Contents (pp. co4).

Editorial Board (pp. co2).

Contents Continued (pp. i).

Editorial Board (pp. i).

Preparation of the visible light responsive N³⁻-doped WO₃ photocatalyst by a thermal decomposition of ammonium paratungstate by Masato Takeuchi; Yukari Shimizu; Hiromasa Yamagawa; Tomoyoshi Nakamuro; Masakazu Anpo (pp. 1-5).

Display Omitted► The nitrogen doped WO₃ was prepared by a thermal decomposition of an ammonium paratungstate. ► The Pt-loaded N-WO₃ photocatalyst efficiently decomposed methanol into CO₂ and H₂O under solar light irradiation. ► The Pt particles on the N-WO₃ as a cocatalyst showed a high oxidation catalysis property at 323–333K.The nitrogen doped WO₃ (N-WO₃) photocatalyst was successfully prepared by a thermal decomposition of an ammonium paratungstate [(NH₄)₁₀W₁₂O₄₁·5H₂O] containing NH₄⁺ ions as a nitrogen source. The N-WO₃ prepared at 673–873K efficiently absorbed visible light in longer wavelength regions as compared to a commercial N-free WO₃. Although small amount of Pt particles must be deposited on the catalyst surfaces, the N-WO₃ photocatalysts were found to decompose gaseous methanol into CO₂ and H₂O under visible or solar light irradiations. As well as, the Pt particles on the N-WO₃ surfaces to enhance the photocatalytic activity showed an oxidation catalysis property at low temperatures of 323–333K. These results suggest that the N-WO₃ deposited with Pt particles can effectively utilize the sunlight as light and/or heat sources.

Keywords: N-doped WO; ₃; Visible light responsive photocatalyst; Focused sunlight

Photodegradation of methyl orange and 2,3-butanedione on titanium-dioxide nanotube arrays efficiently synthesized on titanium coils by Vance Jaeger; Winn Wilson; Vaidyanathan (Ravi) Subramanian (pp. 6-13).

Display Omitted► TiO₂ nanotubes (T-NT) on coils identical to T-NT on foil and mesh. ► Methyl orange degradation using T-NT on-coil ( X=0.5)>Mesh ( X=0.3)>foil ( X=0.2). ► Gas phase degradation of diacetyl vapors using T-NT on coils show X=0.45. ► T-NT on coils offer minimal (i) dark spots and (ii) recombination centers.This work presents the synthesis, characterization, and application of titanium dioxide nanotube arrays (T-NT) prepared on titanium coils by anodization. A comparison of the physical, photoelectrochemical, and photocatalytic properties of T-NT on coil, mesh, and foil architectures is reported. The application of T-NT on helical coils to UV–vis initiated photodegradation of pollutants in aqueous and gaseous phases is discussed. The T-NT on coil shows better photoactivity compared to T-NT on other geometries such as foil and mesh. A 30% increase in the photodegradation of methyl orange in the aqueous phase is noted with T-NT on coils compared to T-NT on mesh. T-NT on coils also demonstrate photodegradation of a model pollutant 2,3-butanedione (diacetyl) in the gaseous phase. The T-NT grown on the coil architecture offer several advantages such as significantly minimized dark spots, highly reduced recombination centers, as well as adjustable spacing and dimensions for tuning photo(electro)catalytic activity. This configuration can be useful in other non-photocatalytic applications as well.

Keywords: Photocatalysis; TiO; ₂; nanotubes; Methyl orange; Diacetyl vapors; Coil

An experimental and modelling investigation of the effect of the flow regime on the photocatalytic degradation of methylene blue on a thin film coated ultraviolet irradiated spinning disc reactor by Irina Boiarkina; Simon Pedron; Darrell A. Patterson (pp. 14-24).

Display Omitted► Degradation of methylene blue in a thin film photocatalytic spinning disc reactor. ► Liquid fed onto centre of horizontally spinning disc spreading out into a thin film. ► Wave regime showed no effect on degradation rate due to laminar dominated flow. ► Photonic efficiency is independent of liquid film height. ► Two reaction rate maxima observed at 15mL/s and 100 and 200rpm.In this work, the impact of wave regime and operational parameters on the photocatalytic degradation of methylene blue was investigated on a thin film coated ultra-violet spinning disc. In the employed experimental setup, the wave regimes of spiral, unstructured and crisscross waves as well as smooth film could be observed at disc rotational speeds of 50–200rpm and flow rates of 5–20mL/s with a calculated average thickness of 160–450μm. The glass discs were coated with anatase TiO₂ by a sol–gel procedure followed by heat treatment at 500° C for 1h. The reactor was irradiated by a low pressure mercury UV lamp producing an irradiance of 12–23W/m² on the disc surface. The reactant was saturated with oxygen and the effect of spinning speed, flow rate and the resulting wave regime on the degradation rate and kinetics of methylene blue and its reaction intermediates determined. Reactions followed pseudo-second-order kinetics, suggesting dimerisation and/or mass transfer limitations given that the two reactions with the highest conversion observed at 15mL/s and 100 and 200rpm, were pseudo-first-order. The spinning disc reactor was, however, not photon transfer limited. The wave regimes showed no impact on the reaction rate, since the flow was mainly laminar with no interfacial mass transfer of oxidant required.

Visible light active Fe doped TiO₂ nanowires grown on graphene using supercritical CO₂ by Nasrin Farhangi; Rajib Roy Chowdhury; Yaocihuatl Medina-Gonzalez; Madhumita B. Ray; Paul A. Charpentier (pp. 25-32).

Display Omitted► Graphene sheets used as a catalyst mat to grow Fe doped TiO₂ nanofibers from its surface in the green solvent, supercritical carbon dioxide. ► High surface areas and direct attachment were shown by several physico-chemical techniques. ► 17β-Estradiol (E2) was completely degradated by this catalyst in the visible region. ► Fe doped TiO₂ on the graphene sheets showed higher photocatalytic activity compared to similar catalyst without graphene.Visible light driven TiO₂ photocatalyst nanowire arrays doped with Fe were grown on the surface of functionalized graphene sheets (FGSs) using a sol–gel method in the green solvent, supercritical carbon dioxide (scCO₂). The morphology of the synthesized catalysts was studied by SEM and TEM, which showed uniform formation of Fe doped TiO₂ nanowires on the surface of the graphene sheets, which acted as a template for nanowire growth through surface –COOH functionalities. Increasing Fe content in the nanowires gave only small changes in morphology but significantly higher BET surface areas. Optical properties of the synthesized composites were examined by UV and PL spectroscopy which showed a significant reduction in band gap with increasing Fe content, i.e. decreasing from 3.2 to 2.3eV at 0.6% Fe. High resolution XPS and Raman analysis showed the interaction of Fe with the TiO₂ lattice and also bonding of TiO₂ with –COOH groups on the surface of the graphene sheets. The photocatalytic properties of the prepared catalysts were evaluated under visible light solar irradiation for the photodegradation of 17β-estradiol (E2), an endocrine disrupting hormone which is commonly released into aquatic environments. All prepared catalysts with different ratios of Fe were active in the visible region of the solar spectrum with the photocatalytic activity significantly enhanced with increasing Fe doping levels with a plateau at 0.6–0.8% Fe. The prepared catalysts showed higher activity than both Fe doped TiO₂ and TiO₂/FGSs composites.

Keywords: Fe doped TiO; ₂; /graphene sheets; Super critical carbon dioxide; Sol–gel method; Band gap reduction; Electron hole recombination; Photocatalyst

Mechanistic analysis of direct N₂O decomposition and reduction with H₂ or NH₃ over RuO₂ by Marta Santiago; Vita A. Kondratenko; Evgenii V. Kondratenko; Núria López; Javier Pérez-Ramírez (pp. 33-39).

Steady-state catalytic tests at ambient pressure, transient studies in the TAP reactor, and DFT simulations were applied to investigate the mechanism of N₂O decomposition and N₂O reduction by H₂ or NH₃ on RuO₂.Display Omitted► De-N₂O mechanism on RuO₂ using experimental and theoretical methods. ► O₂ evolution is rate-limiting step in direct N₂O decomposition. ► Vacant sites generated by H₂ pre-reduction of RuO₂ are highly active. ► H₂ is a more effective reducing agent for N₂O than NH₃. ► Surface NH_x intermediates and O₂ block sites for N₂O decomposition.The mechanisms of direct N₂O decomposition and N₂O reduction by H₂ or NH₃ on RuO₂ has been studied by means of steady-state catalytic tests at ambient pressure, transient experiments in a temporal analysis of products (TAP) reactor, and density functional theory (DFT) simulations. Bulk RuO₂ is very active for N₂O decomposition into N₂ and O₂, achieving full conversion at 723K. According to the DFT calculations, coordinatively unsaturated ruthenium (Ru_cus) sites are active for the decomposition and oxygen elimination from the surface is rate-limiting step. When pre-reducing RuO₂ with H₂, the de-N₂O activity in the low-temperature region increases. This is attributed to the higher reactivity of surface oxygen vacancies created by H₂ at bridge sites compared to Ru_cus sites. Co-feeding of hydrogen or ammonia with nitrous oxide strongly accelerates the rate of N₂O elimination. TAP studies show that oxygen species formed upon N₂O decomposition over RuO₂ react with NH₃ and H₂ yielding N₂, NO, N₂O, and H₂O. Both TAP experiments and DFT simulations show that the N-containing intermediates coming from ammonia adsorb much stronger on the catalyst surface than H-containing intermediates coming from hydrogen. This causes blockage of active sites for N₂O decomposition by the former species, accounting for the higher efficiency of H₂ as reductant for N₂O. The presence of O₂ in the feed cancels the reducing effect of H₂ or NH₃ due to the more favorable re-oxidation of reduced RuO₂ by O₂ compared to N₂O.

Keywords: N; ₂; O decomposition; RuO; ₂; Hydrogen; Mechanism; Temporal analysis of products; Density functional theory

Enhancement of catalytic properties for glycerol electrooxidation on Pt and Pd nanoparticles induced by Bi surface modification by Mário Simões; Stève Baranton; Christophe Coutanceau (pp. 40-49).

. Polarization curves of glycerol oxidation recorded on (a) Pt/C, Pd/C, Pd_0.9Bi_0.1/C and (b) Pt/C, Pt_0.9Bi_0.1/C and Pd_0.45Pt_0.45Bi_0.1/C ( v=10mVs⁻¹, N₂-saturated, 0.1M glycerol+1.0M NaOH electrolyte, T=293K).Display Omitted► Pd or Pt modification by Bi increases the catalytic activity for glycerol oxidation. ► Platinum-free Pd_0.9Bi_0.1/C displays same catalytic activity as Pt/C. ► Order of activity is Pd/C0.9Bi_0.1/C0.9Bi_0.1/C=Pd_0.45Pt_0.45Bi_0.1/C. ► Glycerol adsorption at low potentials on PdBi and PdBi bismuth is non-dissociative. ► Modification by Bi does not change the glycerol oxidation mechanism; potential does.Effects toward electrocatalytic activity for glycerol oxidation of the modification of carbon supported Pd and Pt-based nanomaterials by bismuth were evaluated in alkaline medium. Pd/C, Pd_0.9Bi_0.1/C, Pt/C, Pt_0.9Bi_0.1/C and Pd_0.45Pt_0.45Bi_0.1/C catalysts were synthesized by a colloidal route, and physical and electrochemical methods were used to characterize the structure and the surface of the catalysts (TEM, HRTEM, EDX, XRD, ICP-OES and XPS). It was shown that only a few amount of bismuth was deposited on the Pt and/or Pd surface, and that no alloy was formed between bismuth and the other metals. The onset potential of glycerol oxidation is ca. 0.15V lower on Pt/C than on Pd/C. However, Pt-free Pd_0.9Bi_0.1/C catalyst presented the same catalytic activity than platinum catalyst. The Pt_0.9Bi_0.1/C led reaching a higher catalytic activity by shifting the oxidation onset potential by ca. 0.2V toward lower potentials compared with the Pt/C catalyst. But, the replacing of half of the platinum atoms by palladium atoms in the Pd_0.45Pt_0.45Bi_0.1/C material allowed achieving the same catalytic activity as with Pt_0.9Bi_0.1/C. Electrochemical experiments combined with in situ infrared spectroscopy measurements have shown that glycerol electrooxidation mechanism is independent on the catalyst, but dependent on the electrode potential. Chronoamperometry experiments combined with HPLC measurements showed that the main reaction products were glycerate, dihydroxyacetone and tartronate at low potentials, and that the increase of the electrode potential led to the formation of mesoxalate. For potential higher than 0.8V vs RHE, the C–C bond cleavage occurred and oxalate and formiate were detected.

Keywords: Alkaline fuel cell; Bismuth; Glycerol; HPLC; In situ; infrared spectroscopy; Palladium; Platinum

Carbon nanotube/titanium dioxide (CNT/TiO₂) core–shell nanocomposites with tailored shell thickness, CNT content and photocatalytic/photoelectrocatalytic properties by Ziyan Li; Bin Gao; George Zheng Chen; Robert Mokaya; Sotiris Sotiropoulos; Gianluca Li Puma (pp. 50-57).

Display Omitted► CNT/TiO₂ nanocomposites with tailored uniform core–shell coatings were fabricated. ► Different titania precursors led to differences in TiO₂ thickness and CNT contents. ► TiO₂ film thickness is the key factor controlling photocatalytic activity in slurries. ► Higher CNT content correlates with higher photocurrents in immobilized composites. ► The composite prepared from titanium butoxide was photocatalytically the most active.Combining carbon nanotubes (CNTs) with TiO₂ at the nano-scale level can promote the separation of the electron–hole charges generated upon irradiation. However, charge separation capability depends on the quality of the interfacial contact between CNTs and TiO₂, and on the morphological and surface properties of the nanocomposites. In this study, CNT/TiO₂ nanocomposites with tailored uniform core–shell coatings were fabricated from different titania precursors (titanium ethoxide (TEOTi), titanium isopropoxide (TTIP) and titanium butoxide (TBT)) by surfactant wrapping sol–gel method. This method produces a uniform and well-defined nanometer-scale anatase titania (TiO₂) layer on individual CNT (multi-walled), producing a mesoporous nanocomposite film. The composites were characterized by a range of analytical techniques including TEM, XRD, BET, TGA and UV–vis to reveal the textural, crystallographic and optical properties of the composites. The nanocomposites produced from the different Ti precursors exhibited significant differences in photocatalytic activity and photocurrent within the experimental range. A thinner TiO₂ layer provides shorter distance for electron transfer to the CNT core enhancing photocatalytic activity (degradation of methylene blue). However, higher CNT content in the composites correlates with higher photocurrents. It is shown that TiO₂ film thickness is the key factor controlling electron transfer and photocatalytic activity in CNT/TiO₂ nanocomposites with a core–shell structure, when the catalyst is applied in an irradiated slurry suspension. However, it is the electronic conductivity of the nanocomposite catalyst film, which increases with CNT content that controls the rate of electron removal from the photocatalyst when it is subject to an external positive bias in an appropriate photo-electrochemical cell. Overall, the CNT/TiO₂ composite prepared from TBT performed significantly better than those prepared from TEOTi and TTIP.

Keywords: CNTs; Nanotubes; Photocatalysis; Surfactant; Wrapping; Photo-oxidation; Nanostructure; Semiconductor; Photocatalytic; Photoelectrocatalysis

Catalytic reduction of nitrates in water on Pt promoted Cu hydrotalcite-derived catalysts: Effect of the Pt–Cu alloy formation by A. Aristizábal; S. Contreras; N. Barrabés; J. Llorca; D. Tichit; F. Medina (pp. 58-70).

. Proposed scheme of the Pt–Cu metallic states in the catalytic reduction of nitrates in water.Display Omitted► Pt/CuMgAl calcined HT are tested for the catalytic reduction of nitrates in water. ► Synthesis method influences catalytic activity due to different Pt–Cu interactions. ► Double impregnation method maximizes the nitrate conversion. ► Pt–Cu alloy formation favors nitrogen selectivity and nitrite reduction. ► Pt–Cu alloy formation affects negatively the nitrate conversion.In this work, the role of the Pt–Cu interaction and the influence of the Pt metal loading in the catalytic reduction of nitrates in water have been studied, using Pt supported on CuMgAl mixed oxides catalysts in a continuous reactor. Following three Pt impregnation protocols different surface chemistries were obtained, as confirmed by BET, TPR, HRTEM, XRD and FTIR spectroscopy. In the first protocol, the presence of Cu and Pt–Cu alloy formation has been promoted, whereas the second protocol leads to separated Pt and Cu particles in close contact. The third protocol leads to the presence of Cu, Pt and Pt–Cu alloy particles. The different catalytic behaviors were related to the differences in the surface metal chemistry of the samples. Low ammonium formation was detected in all cases but nitrite concentrations need to be improved to fulfill the maximum admissible concentration of the EU legislation. It is concluded that: (i) the presence of Pt–Cu alloy particles leads to an increase in nitrogen selectivity, enhancing the nitrite reduction but showing lower nitrate conversion, and (ii) to maximize the nitrate conversion it is necessary to obtain mainly Pt particles interacting with Cu and Pt–Cu alloy particles.

Keywords: Catalytic hydrogenation of nitrates; Hydrotalcite; Alloy formation; Pt–Cu

Low temperature selective catalytic reduction of NO with NH₃ over Mn–Fe spinel: Performance, mechanism and kinetic study by Shijian Yang; Chizhong Wang; Junhua Li; Naiqiang Yan; Lei Ma; Huazheng Chang (pp. 71-80).

.Display Omitted► Mn–Fe spinel shows an excellent low temperature SCR activity. ► The SCR activity is promoted with the increase of Mn content. ► The SCR reaction over (Fe_2.5Mn_0.5)1−_δO₄ mainly follows the E–R mechanism. ► Catalyst deactivated by SO₂ can be regenerated through water washing.(Fe3−_xMn_x)1−_δO₄ was synthesized using a co-precipitation method and then developed as a catalyst for the low temperature selective catalytic reduction (SCR) of NO with NH₃. The SCR activity of (Fe3−_xMn_x)1−_δO₄ was clearly enhanced with the increase of Mn content. The results of in situ DRIFTS study demonstrated that both the Eley–Rideal mechanism (i.e. reaction of activated ammonia with gaseous NO) and the Langmuir–Hinshelwood mechanism (i.e. reaction of adsorbed ammonia species with adsorbed NO_x species) might happen during the SCR reaction over (Fe3−_xMn_x)1−_δO₄. According to the kinetic analysis, the respective contribution of the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism on the SCR reaction was studied. Only the adsorption of NO+O₂ on (Fe_2.8Mn_0.2)1−_δO₄ was promoted, so the Langmuir–Hinshelwood mechanism predominated over NO conversion on (Fe_2.8Mn_0.2)1−_δO₄ especially at lower temperatures. Both the adsorption of NO+O₂ and the adsorption of NH₃ on (Fe_2.5Mn_0.5)1−_δO₄ were obviously promoted, so NO conversion on (Fe_2.5Mn_0.5)1−_δO₄ mainly followed the Eley–Rideal mechanism especially at higher temperatures. Both the nitrate route and the over-oxidization of adsorbed ammonia species contributed to the formation of N₂O on (Fe_2.8Mn_0.2)1−_δO₄ above 140°C. However, the formation of N₂O on (Fe_2.5Mn_0.5)1−_δO₄ mainly resulted from the over-oxidization of adsorbed ammonia species. Although the activity of (Fe_2.5Mn_0.5)1−_δO₄ was suppressed in the presence of H₂O and SO₂, the deactivated catalyst can be regenerated after the water washing.

Keywords: Low temperature SCR; (Fe; 3−; _x; Mn; _x; ); 1−; _δ; O; ₄; Kinetic analysis; N; ₂; O origination

Sewage sludge based carbons for catalytic wet air oxidation of phenolic compounds in batch and trickle bed reactors by F. Stüber; K.M. Smith; M. Baricot Mendoza; R.R.N. Marques; A. Fabregat; C. Bengoa; J. Font; A. Fortuny; S. Pullket; G.D. Fowler; N.J.D. Graham (pp. 81-89).

Display Omitted► Sewage sludge based activated carbons (SBACs) were prepared for wet air oxidation (WAO). ► The SBACs were viable catalysts for the WAO of phenol, o-cresol and o-chlorophenol. ► The p-nitrophenol molecule was resistant to SBAC catalysed WAO. ► Using CWAO to destroy o-chlorophenol requires a corrosion resistant reactor. ► A hardened SBAC with a high stability was produced using a lignosulphonate binder.The potential of using sludge based activated carbons (SBACs) for catalysing the wet air oxidation (WAO) of phenol, o-cresol, o-chlorophenol and p-nitrophenol was assessed in both a batch slurry reactor and a continuous trickle-bed reactor. In the batch reactor, the activity of two powdered carbons prepared from, respectively, dewatered raw (DRAW) sludge and dewatered, mesophilic anaerobically digested (DMAD) sludge was tested at 160°C and 4.2bar of oxygen partial pressure. Continuous, trickle-bed reactor experiments of up to 72h were conducted at similar operating conditions to study the durability and catalytic wet air oxidation (CWAO) performance of three economically promising steam activated SBACs. Due to their low mechanical strength, the two DRAW derived SBACs tested were produced using two different attrition resistance enhancement techniques. A commercial activated carbon (Chemviron, AP4-X) was employed as the reference catalyst for all of the tests.In the batch runs, the SBACs and AP4-X achieved high levels of pollutant conversion in the case of phenol, o-cresol and o-chlorophenol. However, irrespective of the carbon tested, p-nitrophenol was resistant to oxidation. When employed in the trickle-bed reactor, the DRAW derived SBAC pelletised using a lignosulphonate binder was found to be the most stable carbon. With this carbon the order of compound reactivity was as observed in the batch experiments.

Keywords: Catalytic wet air oxidation; Activated carbon; Sewage sludge; Wastewater treatment; Phenolic compounds; Trickle bed reactor

Activity and stability of BaKCo/CeO₂ catalysts for diesel soot oxidation by María Ariela Peralta; María Soledad Zanuttini; Carlos Alberto Querini (pp. 90-98).

Display Omitted► Stability of BaCoK/CeO₂ catalysts is studied. ► The preparation procedure has a major impact on the activity and stability. ► Catalyst obtained by successive impregnations using Co(NO₃)₂ are the more active. ► The presence of Ba(NO₃)₂ improves the stability when SO₂ is present. ► The catalyst in the presence of CO₂+NO+H₂O+O₂ preserves its composition.The activity and stability of Ba,K,Co/CeO₂ catalyst in the diesel soot oxidation reaction are studied. Different modes of preparation are analyzed, varying both the cobalt precursor and its order of impregnation. In order to study the stability in a diesel exhaust atmosphere, the catalysts were pretreated in streams of CO₂, H₂O, NO and SO₂. The fresh and the treated catalysts were characterized by FTIR and XRD techniques. The catalytic activity was measured by TPO of soot–catalyst mixtures. The tight contact was used to analyze the intrinsic activity. It was found that the activity was higher for the catalysts prepared using Co(NO₃)₂ compared with the catalysts prepared using Co(AcO)₂. This is because in the former, KNO₃ is present on the catalyst, being this compound very active for this reaction. The thermal stability is lower for the catalyst prepared with Co(NO₃)₂. This catalyst displays a higher K lost when treated at high temperature. When K is present as K₂CO₃, as is the case of the catalysts prepared with Co(AcO)₂, the thermal stability is higher since K₂CO₃ is less volatile than KNO₃. All the catalysts are stable in the presence of mixtures of (CO₂+H₂O+NO+O₂) having a composition similar to a real diesel exhaust. Under these conditions, the K mantains its original chemical state, either carbonate or nitrate, depending on the precursor used in the catalyst preparation. In presence of SO₂, all the catalysts deactivate due to K₂SO₄ formation, which is not active for soot combustion. However, the sensitivity to SO₂ depends on the precursors used to prepare the catalyst. The Ba,K,Co/CeO₂ catalyst prepared impregnating Co(NO₃)₂ on the Ba,K/CeO₂ catalyst has a higher resistance to the deactivation by SO₂, since the following reaction occurs:Ba(NO3)2+K2SO4→BaSO4+KNO3, which implies that active KNO₃ will dissapear slower from the catalytic surface, thus maintaining the activity. TPO experiments of the catalyst in loose contact with soot were also carried out. The Ba,K,Co/CeO₂ catalyst prepared impregnating Co(NO₃)₂ on the Ba,K/CeO₂ catalyst showed the higher activity in loose contact mode.

Keywords: Diesel soot; Cobalt; Potassium; Barium; Cerium oxide; Catalyst stability

Photocatalytic activity of CdS and Ag₂S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes by Gururaj M. Neelgund; Aderemi Oki (pp. 99-107).

Two ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag₂S, comprised of multiwalled carbon nanotubes (MWCNTs), poly(amidoamine) and CdS or Ag₂S quantum dots were successfully synthesized and examined for their photocatalytic activity. The structural transformation, surface potential, and morphology of functionalized MWCNTs and nanocatalysts were characterized by UV–vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy.Display Omitted► Constructed novel nanocatalysts are promising reusable photocatalysts. ► PAMAM dendrimers are very effective in replacing the van der Waals force of pristine MWCNTs. ► Structure of MWCNTs is well retainable after covalent grafting of PAMAM also. ► Presence of PAMAM dendrimers on the surface of MWCNTs was observed by TEM. ► Strong interaction between f-MWCNTs and QDs results in the generation of more active sites.Two novel ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag₂S were successfully constructed by covalent grafting of fourth generation (G4) hyperbranched, crosslinked poly(amidoamine) (PAMAM) to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and subsequent deposition of CdS or Ag₂S quantum dots (QDs). The structural transformation, surface potential, and morphology of functionalized MWCNTs ( f-MWCNTs) and nanocatalysts were characterized by UV–vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. Transmission electron microscopy reveals the effective anchoring of QDs on f-MWCNTs. The catalytic activity of nanocatalysts was evaluated by photodegradation of methyl orange under illumination of UV light. The coupling of MWCNTs, PAMAM and CdS or Ag₂S QDs significantly enhanced the catalytic efficiency of nanocatalysts. The rate constants for degradation of methyl orange in presence of nanocatalysts were calculated using the Langmuir–Hinshelwood model. Overall, the excellence in photodegradation was accomplished by hybridizing f-MWCNTs with CdS or Ag₂S QDs.

Keywords: Carbon nanotubes; Cadmium sulfide; Silver sulfide; Poly(amidoamine); Photocatalyst

Methylene blue photodegradation over titania-decorated SBA-15 by Y.J. Acosta-Silva; R. Nava; V. Hernández-Morales; S.A. Macías-Sánchez; M.L. Gómez-Herrera; B. Pawelec (pp. 108-117).

Mesoporous x%TiO₂/SBA-15 matrices with different amount of TiO₂ (7.3–31.1wt.%) were prepared by impregnation of the synthesized SBA-15 with titanium (IV) isopropoxide in 2-propanol. The x% TiO₂/SBA-15 photocatalysts were found to be more active than pure anatase titania and this increase was linear with TiO₂ loading. The highest activity of 31% TiO₂/SBA-15 sample was explained in terms of the combined factors such as a high crystallinity of anatase phase, preservation of a high surface area, a large amount of the surface hydroxyl groups, and a larger accessibility of photo-oxidative sites.Display Omitted► Mesoporous TiO₂/SBA-15 matrices as photocatalysts. ► Photocatalysts for the degradation of methylene blue. ► Particle size and photocatalytic properties were found to depend on the TiO₂ loadings. ► TiO₂/SBA-15 composite is more active than pure TiO₂. ► Textural characteristics of mesoporous materials have great influence on the catalytic activity.Santa Barbara Amorphous (SBA-15) mesoporous materials decorated with vary amount of TiO₂ (7–31% TiO₂/SBA-15) were prepared by the post-synthesis method from previously synthesized SBA-15 and their photocatalytic activity toward the degradation of methylene blue (MB) was measured. Nonionic surfactant was used as liquid template and tetraethyl orthosilicate (TEOS) as SiO₂ precursor for the synthesis of mesoporous silica SBA-15. The synthesized x% TiO₂/SBA-15 materials were characterized by N₂ adsorption–desorption isotherms, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), micro-Raman spectroscopy, infrared spectroscopy of framework vibration (IR-KBr) and X-ray photoelectron spectroscopy (XPS). The x% TiO₂/SBA-15 photocatalysts were found to be more active than pure anatase titania and this increase was linear with TiO₂ loading. The highest activity of 31% TiO₂/SBA-15 sample was explained in terms of the combined factors such as a high crystallinity of anatase phase, preservation of a high surface area, a large amount of the surface hydroxyl groups, and a larger accessibility of photo-oxidative sites. A linear correlation between the apparent first order rate constants ( k_app) and the amount of TiO₂ species located within porous structure of the SBA-15 substrate was found.

Keywords: Photocatalysis; Methylene blue; Mesoporous matrices; Titania; SBA-15

A highly active bimetallic oxides catalyst supported on Al-containing MCM-41 for Fenton oxidation of phenol solution by Min Xia; Mingce Long; Yudong Yang; Chen Chen; Weimin Cai; Baoxue Zhou (pp. 118-125).

Display Omitted► A new Fe-Cu bimetallic supported aluminum-containing MCM-41 was synthesized. ► The catalyst displayed enhanced activity and stability in the phenol mineralization via a heterogeneous Fenton reaction. ► The presence of aluminum plays an important role in the activation of H₂O₂.A new heterogeneous Fenton catalyst, Fe-Cu bimetallic oxides supported aluminum-containing MCM-41, was synthesized by co-precipitation method. The physicochemical characteristics of the synthesized samples were evaluated by various techniques such as XRD, TEM, nitrogen physisorption, zeta potential and XPS. The incorporation of metal species did not alter the well-ordered hexagonal mesostructure of MCM-41 support. Compared with the monometallic or the Al absent catalysts, this new bimetallic oxides supported aluminum-containing MCM-41 catalyst exhibited a higher activity and stability in phenol mineralization. The effects of temperature, pH and H₂O₂ dosage were investigated in terms of the TOC conversion. At pH 4, 60°C and 0.049mol/L of H₂O₂ dosage, a 47% TOC reduction has been achieved. With incorporating aluminum, the increase in surface oxygen-containing groups was observed by zeta potential analysis, the downshift binding energy of active metals was found by XPS measurement, and an enhancement of H₂O₂ utilization ratio was achieved. On the basis of our findings, the beneficial role of Al has been explained.

Keywords: Bimetallic oxides; Aluminum; MCM-41; Heterogeneous; Fenton

Photocatalytic bleaching of aqueous malachite green solutions by UV-A and blue-light-illuminated TiO₂ spherical nanoparticles modified with tungstophosphoric acid by J.A. Rengifo-Herrera; M.N. Blanco; L.R. Pizzio (pp. 126-132).

Display Omitted► Vis-light-responsive TiO₂ modified with tungstophosphoric acid (TPA) was obtained. ► TPA and their lacunar and dimeric phases were detected on TPA–TiO₂ materials. ► Presence of WO_x species on TPA–TiO₂ could be responsible of Vis-light absorption. ► Irradiated TPA–TiO₂ bleached efficiently malachite green (MG) solutions. ► MG underwent N-demethylation induced by UV and blue-light irradiated TPA–TiO₂.Visible-light-responsive spherical TiO₂ particles were prepared by the sol–gel method by adding urea as pore-forming agent and tungstophosphoric acid (TPA) in different ratios (20% and 30% w/w) and by annealing at 500°C for 2h. Visible light absorption is probably due to WO_x formation (i.e. WO₃) resulting from the partial degradation of TPA and evidenced by XPS spectra. Besides,³¹P NMR and XPS results showed evidence about the existence of mostly unaltered TPA within TiO₂ nanoparticles and on their surface, together with lacunar or dimeric species. TPA addition not only affected the optical properties of materials but also produced a strong decrease of their point of zero charge (pH_pzc). Results obtained under UV-A irradiation revealed that aqueous malachite green (MG) solutions were efficiently bleached through the oxidative process of N-demethylation being the TiO₂ powder containing 30% (w/w) of TPA (TiO₂–TPA–30%) (100% of bleaching in 60min) the most active even than Degussa P-25 (80% of MG bleaching in 60min). On the other hand, when blue-light irradiation was used, TiO₂–TPA–30% powder also revealed the highest photocatalytic bleaching of MG solutions which, as in the case of UV-A light irradiation experiments, was oxidized through N-demethylation processes. Finally, experiments carried out using blue-light irradiation under N₂ atmosphere showed that aqueous MG solutions were not bleached by TiO₂ powders containing TPA.

Keywords: Heterogeneous TiO; ₂; photocatalysis; Tungstophosphoric acid; Malachite green; Visible light responsive TiO; ₂

High combustion activity of CH₄ and catalluminescence properties of CO oxidation over porous Co₃O₄ nanorods by Fei Teng; Mindong Chen; Guiqing Li; Yang Teng; Tongguang Xu; Yechao Hang; Wenqing Yao; Sunand Santhanagopalan; Dennis Desheng Meng; Yongfa Zhu (pp. 133-140).

The highly porous Co₃O₄ nanorods show a higher catalluminescence (CTL) intensity and activity of CO oxidation, and a significantly higher activity for CH4 combustion especially at a high gas hourly space velocity, which has been ascribed to the highly porous structure.Display Omitted► We adopt a simple hydrothermal method to synthesize Co₃O₄ nanorods organized by nanoparticles. ► The sample shows the excellent catalluminescence (CTL) intensity and reactivity of CO oxidation. ► The CTL is a fast mode to screen catalysts from thousands of materials. ► A high activity for CH₄ combustion is obtained especially at a high space velocity. The highly porous structure facilitates the mass transfer particularly at high space velocity.The highly porous Co₃O₄ nanorods are prepared by a simple hydrothermal method, in which CO(NH₂)₂ is employed as precipitating agent, and K60 (PVP, polyvinylpyrrolidone) is used as surfactant to improve the stability of the nanoparticles. For comparison, the bulk Co₃O₄ is prepared by thermal decomposition of cobalt nitrate. The samples are characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (ED), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N₂ adsorption, Thermogravimetric analysis (TG), H₂-temperature programmed reduction (TPR), CO-, CH₄-, and O₂-temperature programmed desorption (TPD). The catalluminescence (CTL) and catalytic properties of the samples are investigated extensively. The results show that the Co₃O₄ nanorods are composed of nanoparticles, and have a large number of pores with a narrow pore size distribution (1.5–7nm). Compared with the bulk Co₃O₄, the porous nanorods have a higher CTL intensity of CO oxidation, and a higher activity of CH₄ combustion especially at a higher gas hourly space velocity (GHSV), which has been ascribed to its porous structure and larger surface area.

Keywords: Porous nanorods; Catalluminescence; Catalytic oxidation, High gas hourly space velocity

PtSn/C alloyed and non-alloyed materials: Differences in the ethanol electro-oxidation reaction pathways by J.C.M. Silva; L.S. Parreira; R.F.B. De Souza; M.L. Calegaro; E.V. Spinacé; A.O. Neto; M.C. Santos (pp. 141-147).

Display Omitted► Ethanol oxidation on Pt₃Sn₁/C alloyed and non-alloyed assisted by FTIR “ in situ”. ► The measured current density for ethanol oxidation on Pt₃Sn/C alloyed is the highest. ► Non-alloyed PtSn/C led to CO₂, while alloyed Pt₃Sn/C led to acetic acid formation.In the present work, the ethanol oxidation reaction (EOR) was investigated using PtSn/C electrocatalysts in the following two phases: 92% alloyed prepared by the polymeric precursor method (PPM) and 6% alloyed prepared by a sol–gel method (SGM). The TEM experiments show particle sizes of 3–5nm for both catalysts. The electrocatalytic activity for both materials was investigated using chronoamperometry, and at 0.5V vs. RHE, the current density for the EOR on the PPM material was approximately 5 times higher than on the SGM material. From in situ ATR-FTIR experiments, it can be seen that the non-alloyed materials led to CO₂ formation with slow kinetics, whereas alloyed materials led to acetic acid formation with fast kinetics. The enhancement in the electrocatalytic behavior for ethanol oxidation was explained by acetic acid formation.

Keywords: PtSn; Ethanol oxidation reaction; Alloyed materials

Comparing Cr, and N only doping with (Cr, N)-codoping for enhancing visible light reactivity of TiO₂ by Yuan Li; Wei Wang; Xiaofeng Qiu; Liang Song; Harry M. Meyer III; M. Parans Paranthaman; Gyula Eres; Zhenyu Zhang; Baohua Gu (pp. 148-153).

Degradation of methyl orange under visible light by Cr-doped and (Cr, N)-codoped TiO₂.Display Omitted► We systematically study the photoreactivity of N- or Cr-doped and (N, Cr)-codoped TiO₂ under both visible and UV light. ► Cr doping and (Cr, N)-codoping red-shift the absorption edge and greatly improve photoreactivities of TiO₂ under visible light. ► (Cr, N)-codoping does not show improved visible light activity as compared with the Cr-doped TiO₂. ► Doping and codoping with N and Cr are all detrimental to photoreactivity under UV light.The photoreactivity of titania (TiO₂) nanoclusters with varying levels of N or Cr-doping, or (Cr, N)-codoping, was systematically investigated using photodegradation of methyl orange in aqueous suspensions. The shifting of the TiO₂ absorption edge into the visible spectral region that is primarily attributable to band gap narrowing was found to be a reliable metric for estimating the photoreactivity of the doped nanoclusters. Compared to the weak response with undoped and N-doped TiO₂, Cr-doping and (Cr, N)-codoping were found to significantly enhance photodegradation of methyl orange under visible light. The initial reaction rates increase from about 0 to above 1.6×10⁻²min⁻¹ when the doping concentration of Cr in TiO₂ increases from 0 to 5%. In stark contrast, under UV irradiation, doping is not only ineffective but also detrimental to the photoreactivity, and all doping including N or Cr only and (Cr, N)-codoping were found to reduce photoreactivity.

Keywords: Titania; Nanoclusters; Cation–anion codoping; Photodegradation; Solar energy

Mesoporous ceria-zirconia supported cobalt oxide catalysts for CO preferential oxidation reaction in excess H₂ by Zhongkui Zhao; Ronghua Jin; Ting Bao; Xiaoli Lin; Guiru Wang (pp. 154-163).

Display Omitted► Mesoporous ceria-zirconia is an appropriate support to stabilize high-valence Co³⁺. ► The high-valence cobalt is the main active species for CO PROX in excess H₂. ► Residual sulfur from ADBS significantly affects catalytic properties for CO PROX. ► It is a robust and effective catalyst for CO PROX even with CO₂ and H₂O in the feed. ► Catalytic properties highly depend on the dispersion of Co₃O₄ and redox of catalyst.Mesoporous Co₃O₄/Ce_xZr1−_xO₂ ( x=0.75, 0.85, 0.95, 1) catalysts were synthesized by surfactant-assisted co-precipitation with subsequent incipient wetness impregnation (SACP-IWI) method. The prepared mesoporous ceria-zirconia supported cobalt oxide catalysts were used to catalyze CO preferential oxidation (PROX) reaction to eliminate the trace CO from H₂-rich gases. The effects of structure-directing agent (SDA) type, atomic ratio of Ce/(Ce+Zr), cobalt oxide loading and reaction parameters on the catalytic properties for CO PROX reaction in excess H₂ were investigated. Moreover, the various characterization techniques like N₂ adsorption/desorption, X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), NH₃ temperature-programmed desorption (NH₃-TPD), Fourier-Transform infrared spectroscopy (FT-IR) were employed to study the relationship between catalyst nature and catalytic properties. The results of N₂ adsorption/desorption and X-ray diffraction patterns indicate that catalysts prepared by using cationic surfactant cetyltrimethylammonium bromide (CTAB) as SDA possess an ordered mesoporous architecture and exhibit much better catalytic activity compared with those prepared by using anionic surfactant ammonium dodecylbenzenesulfonate (ADBS) as SDA. The residual sulfur from ADBS was demonstrated to be the main reason for the much worse catalytic performance by the characterization results of FT-IR and NH₃-TPD. Results show that the developed Co₃O₄/ meso-Ce_0.85Zr_0.15O₂ catalysts by SACP-IWI method with CTAB as SDA show an outstanding catalytic performance for CO PROX reaction, which mainly depends on the redox behavior of catalyst and cobalt oxide dispersion affected by the ceria-zirconia support feature, atomic ratio of Ce/(Ce+Zr) of support and cobalt oxide loading.

Keywords: Mesoporous ceria-zirconia composite; Cobalt oxide loading; Structure-directing agent; Ce/(Ce; +; Zr) atomic ratio; CO preferential oxidation

Electrochemical-catalytic conversion for simultaneous NO_x and hydrocarbons emissions control of lean-burn gasoline engine by Ta-Jen Huang; Chung-Ying Wu; Sheng-Hsiang Hsu; Chi-Chang Wu (pp. 164-170).

Display Omitted► The electrochemical-catalytic cell is effective for emissions control at 400°C. ► The DeNO_x rate can be three orders larger than conventional oxide catalysts. ► The NO conversion can increase with increasing NO_x concentration. ► The NO conversion increases with increasing oxygen concentration. ► Hydrocarbons can be completely oxidized simultaneously.Electrochemical-catalytic conversion via the electrochemical-catalytic cell (ECC) is effective at 400°C for simultaneous NO_x and hydrocarbons emissions control of lean-burn gasoline engine without consuming any reductant. The NO reaction is direct NO decomposition. The NO_x to N₂ rate over the cathode of the ECC can be three orders larger than those over conventional oxide catalysts for NO decomposition. In the high NO_x concentration region, the NO conversion increases with increasing NO_x concentration; this characteristic allows the engine to be operated at high enough temperature with excess oxygen to result in maximum fuel efficiency. In the low NO_x concentration region, the NO conversion also increases with decreasing NO_x concentration; this characteristic enables complete conversion of NO and thus can result in zero NO_x emission. The NO conversion increases with decreasing temperature, at least till 400°C. Higher oxygen concentration is beneficial to both the NO conversion and the hydrocarbons oxidation to result in zero pollution.

Keywords: Nitrogen oxide; Hydrocarbon; Lean-burn gasoline engine; Emissions control; Electrochemical-catalytic cell; Direct NO decomposition

In situ FT-IR investigation on the selective catalytic reduction of NO with CH₄ over Pd/sulfated alumina catalyst by Hongyan Zhang; Lin Li; Ning Li; Aiqin Wang; Xiaodong Wang; Tao Zhang (pp. 171-177).

Display Omitted► Sulfation of alumina generates strong BrØnsted acid sites which can stabilize Pd as isolated Pd²⁺ ions. ► The nitrate species formed over sulfated samples can react with methane under the catalysis of Pd²⁺ ions. ► Co-adsorption of NO and O₂ led to the generation of the intermediate Pd²⁺–NO. This intermediate could readily react with CH₄ and O₂, but almost not react with CH₄ over 350°C.In situ Fourier Transform Infrared (FT-IR) spectroscopy was applied to study the mechanism of the selective catalytic reduction (SCR) of NO with methane over 0.1wt% Pd/sulfated alumina (SA) catalyst. Here, CO adsorption, NO adsorption, NO–O₂ co-adsorption and interaction of the intermediates after NO–O₂ adsorption with methane or methane/oxygen were investigated. The FT-IR results show that the Pd supported on Al₂O₃ mainly exists as oxide, such as PdO cluster. While, the Pd supported on SA mainly exists as isolated Pd²⁺ ions. The addition of Pd can promote the formation of nitro/nitrito and nitrate species on Al₂O₃ or SA at room temperature. At the same time, Pd also promotes the nitrates decomposition at high temperatures. Support sulfation further decreases the total concentration of the nitrates adsorbed on the surface of catalysts and lowers their thermal stability. Moreover, support sulfation can also stabilize isolated Pd²⁺ ions, which could catalyze the reaction between nitrate species and methane. Upon co-adsorption of NO and O₂ on 0.1wt% Pd/SA catalyst, the intermediate Pd²⁺–NO was produced. This intermediate could readily react with CH₄ and O₂, but almost not react with CH₄ over 350°C.

Keywords: Adsorption; NO–O; ₂; co-adsorption; In situ FT-IR; Nitrates; deNO; _x; CH; ₄; SCR; Pd

Catalytic activity of dendrimer encapsulated Pt nanoparticles anchored onto carbon towards oxygen reduction reaction in polymer electrolyte fuel cells by Tintula Kottakkat; Akhila K. Sahu; Santoshkumar D. Bhat; Pitchumani Sethuraman; Sridhar Parthasarathi (pp. 178-185).

Display Omitted► Hydroxyl-terminated poly(amidoamine) dendrimer controls Pt nanoparticle formation. ► Lower loading of Pt is accomplished using this dendrimer regulated catalyst. ► High mass activity and uniform dispersion of Pt is achieved with Pt/G4-OH-C.Pt nanoparticles are encapsulated in the fourth-generation hydroxyl-terminated poly (amidoamine) (PAMAM) dendrimer (G4-OH) and anchored onto carbon to realize a novel cathode catalyst for polymer electrolyte fuel cells (PEFCs). Extensive physical and electrochemical characterizations confirm that Pt/G4-OH-C catalyst exhibits significant enhancement of catalytic activity towards oxygen reduction reaction (ORR). The mass activities (Amg_Pt⁻¹) at 0.9V vs. RHE for Pt/G4-OH-CI and Pt/G4-OH-CII, both prepared by different routes, are enhanced by 3.6 and 2.6 times, respectively, in relation to Pt/C catalyst. Dendrimer template studied here provides size-controlled preparation of Pt-based catalyst and facilitates uniform dispersion and loading of the catalyst onto carbon support. It is noteworthy that a PEFC comprising Pt/G4-OH-C catalyst with a Pt loading of ∼0.1mgcm⁻² delivers a power density of 712mWcm⁻² at 0.6V with H₂ and O₂ feeds. By contrast, the PEFC using Pt/C with a Pt loading of ∼0.2mgcm⁻² delivers a power density of only 370mWcm⁻² while operating under similar conditions.

Keywords: PAMAM dendrimers; Pt nano-catalyst; Oxygen reduction reaction; PEFCs

An innovative electrochemical degradation of 1-diazo-2-naphthol-4-sulfonic acid in the presence of Bi₂Fe₄O₉ by Lin Gu; Fan-Yong Song; Nan-Wen Zhu (pp. 186-194).

Display Omitted► Spinal-like Bi₂Fe₄O₉ was synthesized and functioned as a novel catalyst in the electro-catalyzed system. ► Gas diffusion cathode was chosen as a cathode. ► The degradation of 1-diazo-2-naphthol-4-sulfonic acid was ascribed to the synergetic effect of both catalyst and electrolysis. ► Evolution of intermediates was detected using UPLC-(ESI)-TOF-MS.This paper explores the degradation of a model pollutant, 1-diazo-2-naphthol-4-sulfonic acid (1,2,4-Acid), by an advanced oxidation process that combines electrochemical degradation and Bi₂Fe₄O₉ (BFO) oxidation. Experiments were done using a gas-diffusion cathode to produce in situ hydrogen peroxide by oxygen reduction. Column crystal semiconductor Bi₂Fe₄O₉ was synthesized and used as a novel catalyst in the combined system. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Comparative experiment in two separated systems (BFO/H₂O₂ and BFO/Electrolysis) was conducted to determine the mechanism involved in the process. The effect of operating conditions such as applied current, solution pH, catalyst dosage on the efficacy of the process was investigated. It is shown that 1,2,4-Acid and its products can be effectively degraded by the OH radicals produced by the reaction between BFO and the electro-generated H₂O₂, which was further being confirmed with the electron spin resonance spin-trapping technique. Hydroxyl radicals generated in the process that led to the complete and rapid elimination of total organic carbon was observed even at low catalyst loadings. In this system, almost a complete removal of COD (89%) was achieved after 200min using 1.0gL⁻¹ of BFO, whereas at the same time, only 39% and 32% of COD was removed by an individual process alone (electrochemical degradation and BFO adsorption, respectively). In this combined system, BFO has the principle role of adsorbing the initial substance on the surface of catalyst and catalyzing the electro-generated H₂O₂ to form active hydroxyl radicals. The LC-(ESI)-TOF-MS analysis indicated that the mineralization occurred simultaneous with the destruction of naphthalene ring, and 1,2,4-Acid was oxidized to colourless intermediates (mainly phthalic acid, small carbonyl species) and then to carbon dioxide.

Keywords: Electrochemical degradation; Gas-diffusion electrode; 1,2,4-Acid; Bi; ₂; Fe; ₄; O; ₉

Co-doping a metal (Cr, Fe, Co, Ni, Cu, Zn, Ce, and Zr) on Mn/TiO₂ catalyst and its effect on the selective reduction of NO with NH₃ at low-temperatures by Boningari Thirupathi; Panagiotis G. Smirniotis (pp. 195-206).

Effect of co-doped metals in Mn–M′/TiO₂ catalysts investigated for the selective reduction of NO with NH₃ at low temperatures and in presence of excess oxygen. XPS results illustrated that the MnO₂ phase is extremely dominant over the Mn₂O₃ phase (Mn⁴⁺/Mn³⁺=96%) in the Mn–Ni(0.4)/TiO₂ catalyst. The SCR activity, broadening of temperature window and steady time on stream patterns of the Mn/TiO₂ catalyst are improved greatly by the addition of nickel.Display Omitted► Ni (Ni/Mn=0.4) increases the concentration of surface Mn⁴⁺ sites in Mn/TiO₂ catalyst. ► Co-doping of Mn/TiO₂ with Ni enables 100% NO conversion and N₂ selectivity. ► MnO₂ is the dominant phase in Mn–Ni(0.4)/TiO₂ catalyst. ► Co-doping Mn/TiO₂ with Ni broadens temperature window and catalyst stability. ► Mn–Ni/TiO₂ surface sites have only Lewis acidity, with no Brönsted acidity.A series of Mn–M′/TiO₂ (M′=Cr, Fe, Co, Ni, Cu, Zn, Ce, and Zr) catalysts were prepared using incipient wetness technique and investigated for the low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. A combination of various physico-chemical techniques was used to investigate the influence of co-doped metals on the characteristics of Mn/TiO₂ catalyst. The catalytic performance of these materials was compared with respect to the M′/Mn atomic ratio in order to examine the correlation between physicochemical characteristics and reactivity of optimized materials. XRD results suggest that metal oxide species exist in a highly dispersed state at a certain level called two-dimensional monolayer coverage. Our XPS results illustrated that the MnO₂ phase is extremely dominant over the Mn₂O₃ phase (Mn⁴⁺/Mn³⁺=22.31, 96%) in the Mn–Ni(0.4)/TiO₂ anatase catalyst, whereas Mn₂O₃ phase is in competition with MnO₂ in other catalysts (Mn⁴⁺/Mn³⁺=1.34–12.67). H₂-TPR data results are in good accordance with XPS results that the absence of the high-temperature (736K) peak indicates that the dominant phase is MnO₂ in Mn–Ni(0.4)/TiO₂ catalyst. This increase in reducibility of manganese and dominant MnO₂ phase seems to be the reason for the superior activity and time on stream patterns of our best catalyst. BET and pore volume measurements revealed high surface area and pore volume of the Mn–Ni/TiO₂ catalyst. The in situ NH₃-FTIR results suggest that the manganese (Mn/TiO₂) and manganese–nickel (Mn–Ni/TiO₂) surface sites have only Lewis acidity, with no apparent Brönsted acidity. The catalytic performance of various Mn–M′/TiO₂ (M′/Mn=0, 0.2, 0.4, 0.6, 0.8) catalysts was studied for the low-temperature SCR reaction at a range of temperatures (160–240°C) under industrial conditions using GHSV=50,000h⁻¹. The intrinsic activity of Mn–Ni/TiO₂ catalyst with M′/Mn=0.4 atomic ratio measured under differential reaction conditions, was found to be highly active, selective and broadening the temperature window for this reaction.

Keywords: Low-temperature NH; ₃; -SCR; Manganese oxide (MnO; _x; ); NO; XPS; In situ; FTIR; Optimization for NO reduction

Enhancing the photoelectrochemical performance of hematite (α-Fe₂O₃) electrodes by cadmium incorporation by Ayoung Bak; Wonyong Choi; Hyunwong Park (pp. 207-215).

Display Omitted► The photocurrent of hematite film is four-fold enhanced by Cd doping at 1%. ► Cd exists mainly as CdO and/or Cd(OH)₂ in the hematite surface. ► The photoactive spectral region is red-shifted by Cd doping. ► The primary role of Cd is to increase the electrical conductivity of hematite.Photoelectrochemical (PEC) water oxidation using hematite (α-Fe₂O₃) is of great interest in terms of solar fuels and artificial photosynthesis. In this study, Cd-incorporated nanocrystalline hematite films (Cd–Fe₂O₃) supported on conducting glass have been prepared via co-electrodeposition of aqueous Fe(III) and Cd(II) with varying Cd:Fe atomic ratios (up to 3.2at.%) and optimized for their PEC performances under a simulated solar light (AM 1.5-irradiation). Surface analysis indicates that the Cd co-deposition increases the hematite particle size from ca. 50nm to 70–100nm due to interparticle agglomeration and decreases the overall UV–Vis absorbance of hematite. X-ray photoelectron spectroscopic study also indicates that Cd incorporation shifts the binding energy of oxygen atoms to lower energy direction whereas it does not affect the binding energy of Fe 3d. This suggests that Cd exists mainly as CdO and/or Cd(OH)₂ in the hematite surface. When an optimal level of Cd content (∼1at.%) is electrodeposited, the photocurrent of hematite film is significantly enhanced by a factor of ca. four at E=1.23V_RHE under AM 1.5-irradiation and the photoactive spectral region is red-shifted. Electrochemical impedance spectroscopic analysis further reveals that the flat band potential of hematite is shifted by ca. −30mV to negative potential direction and the charge transfer resistance ( R_ct) is significantly reduced by Cd incorporation. Detailed surface analyses, optimization for preparation condition of hematite films, and discussion for PEC behaviors were described.

Keywords: Electrodeposition; Semiconductor; Water oxidation; Conductivity; Doping

Solvent-free aerobic alcohol oxidation using Cu/Nb₂O₅: Green and highly selective photocatalytic system by Shinya Furukawa; Ayaka Tamura; Tetsuya Shishido; Kentaro Teramura; Tsunehiro Tanaka (pp. 216-220).

Solvent-free aerobic oxidation of alcohols proceeds selectively at room temperature and atmospheric pressure by using Nb₂O₅ or Cu/Nb₂O₅ photocatalysts. Cu/Nb₂O₅ shows remarkably enhanced photocatalytic activity without lowering selectivity than Nb₂O₅ in oxidation of various alcohols.Display Omitted► Solvent-free aerobic oxidation of alcohols using Cu/Nb₂O₅ photocatalyst. ► Enhanced photocatalytic activity of Nb₂O₅ by the addition of Cu. ► The 1-phenylethanol is quantitatively converted to acetophenone under solvent-free and mild conditions.Photooxidation of alcohols without organic solvents in the presence of O₂ took place at the atmospheric pressure and room temperature over Nb₂O₅ and Cu/Nb₂O₅, avoiding the cost, toxicity, and purification problems associated with transition-metal systems. Loading of a small amount of copper on Nb₂O₅ significantly enhanced activity without lowering selectivity. On the other hand, loading of Pt, Ni, Rh, Ru, and Ag showed no promotion effect. The selectivities of the photooxidation of aliphatic, aromatic and heteroatom-containing alcohols over Cu/Nb₂O₅ were in the range of 80–99%. Cu/Nb₂O₅ was easily separated from the reaction mixture and was reusable without reducing the catalytic performance.

Keywords: Alcohol oxidation; Niobium oxide; Photocatalyst; Selective oxidation; Solvent-free

Er³⁺ doped bismuth molybdate nanosheets with exposed {010} facets and enhanced photocatalytic performance by Tengfei Zhou; Juncheng Hu; Jinlin Li (pp. 221-230).

Display Omitted► Upconverter Er³⁺ doped Bi₂MoO₆ nanosheets were synthesized using a simple hydrothermal method. ► Bi₂MoO₆ nanosheets selectively exposed {010} facets at the main external surfaces. ► The photoactivities of the Er³⁺ doped Bi₂MoO₆ nanosheets were much superior to that of Degussa P25. ► The enhanced photocatalytic activity can be attributed to the abundantly exposed {010} facets and the dopant Er³⁺.Er³⁺ doped Bi₂MoO₆ nanosheets with enhanced photocatalytic activity were synthesized for the first time using a simple hydrothermal method. The morphology of Bi₂MoO₆ can be controlled from nanosheets to nanowires by adjusting the pH values. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), photoluminescence spectra (PL) and X-ray photoelectron spectroscopy (XPS). Er³⁺ doped Bi₂MoO₆ nanosheets selectively exposed {010} facets as the main external surfaces and the nanowires grew along the (010) direction. The nanosheets were found to be highly active for photocatalytic degradation of dyes and phenol. The activities of the Er³⁺ doped Bi₂MoO₆ nanosheets were much superior to that of commercial Degussa P25. The effect of Er³⁺ on the photocatalytic activity of Bi₂MoO₆ was investigated in detail. The enhanced photocatalytic activity of Bi₂MoO₆ nanosheets can be attributed to the exposed {010} facets and the dopant Er³⁺ which can transform visible light into ultraviolet light.

Keywords: Upconversion; Erbium; {0; 1; 0} facets; Bismuth molybdate; Photocatalysis

VOCs combustion catalysed by platinum supported on manganese octahedral molecular sieves by O. Sanz; J.J. Delgado; P. Navarro; G. Arzamendi; L.M. Gandía; M. Montes (pp. 231-237).

Partial conversion of toluene and ethyl acetate in the VOCs mixture (B).Display Omitted► OMS-2 has been synthesized and used as catalyst and support for Pt. ► Pt-OMS-2 showed high dispersion and improved the activity for toluene oxidation. ► Pt does not improve the performance of OMS-2 for the oxygenated VOCs combustion. ► In Pt-OMS-2 active sites coexistence for aromatic and oxygenated VOCs combustion.In this work a manganese oxide in the form of octahedral molecular sieve (OMS-2, also called cryptomelane) has been synthesized and used as catalyst and support for Pt. The catalysts were tested and compared with Pt-Al₂O₃ in the combustion of methyl-ethyl-ketone (MEK), toluene, ethyl acetate and a mixture of toluene and ethyl acetate. Bare OMS-2 was significantly active for the combustion of the oxygenated VOCs and in the case of MEK partial oxidation product was detected at intermediate conversion levels. Platinum on OMS-2 showed high dispersion and improved the activity for toluene oxidation, showing a performance better than that of Pt-Al₂O₃. As for the VOCs mixture, Pt-OMS-2 presented the highest combustion activity due to the coexistence of active sites for the total oxidation of both aromatic and oxygenated VOCs. Competitive adsorption effects were not observed with this catalyst that achieved complete conversion of 1000mgC/m³ of VOCs at temperatures below 260°C (1200mgCg_catalyst⁻¹h⁻¹).

Keywords: Pt-OMS-2; Catalytic VOCs combustion; VOCs mixture; Cryptomelane

Photocatalytic transformation of flufenacet over TiO₂ aqueous suspensions: Identification of intermediates and the mechanism involved by V.A. Sakkas; P. Calza; A.D. Vlachou; C. Medana; C. Minero; T. Albanis (pp. 238-250).

Display Omitted► Study of the photolytic and photocatalytic transformation of flufenacet in water. ► We study effects of several important parameters, such as pH values, TiO₂ loading, H₂O₂, and light intensity on flufenacet photocatalysis. ► The optimal experimental condition for flufenacet degradation is obtained. ► We identify 36 phototransformation products using HPLC–HMS and propose a tentative reaction pathway.In order to exploit the efficiency of titania suspensions in photocatalysis for the degradation of the herbicide flufenacet, chemometric optimization tools were employed, such as response surface methodology and experimental design. The aqueous samples were irradiated under a variety of experimental conditions with different amounts of catalyst (TiO₂), electron acceptor (H₂O₂) as well as pH. Results indicated that the degradation efficiency of the herbicide in the experimental domain investigated was mainly affected by the concentration of H₂O₂, followed by TiO₂, pH, as well as their interaction effects.Additionally, the phototransformation products formed during the photocatalytic process were investigated and characterized by means of HPLC/HRMS. The photocatalysed transformation of flufenacet proceeds through the formation of thirty-two (32) products, involving reactions of mono- and di-hydroxylation, dealkylation, detachment of the thiadiazole ring, defluorination on the benzene ring followed by the detachment of the latter ring. The thiadiazole ring appears to be involved in the process to a lesser extent and only as a secondary path. The measurement of acute toxicity, evaluated using the Vibrio fischeri bacteria test, showed that the transformation of flufenacet proceeds through the formation of compounds more toxic than the parent molecule. Although the identified intermediates were easily degraded and within two hours of irradiation were completely disappeared, mineralization was much slower and complete formation of CO₂ and inorganic constituents was only achieved after 24h of irradiation.

Keywords: Photocatalysis; TiO; ₂; Experimental design; Mineralization; Toxicity; Flufenacet

Highly selective one-dimensional TiO₂-based nanostructures for air treatment applications by María D. Hernández-Alonso; Sergio García-Rodríguez; Silvia Suárez; Raquel Portela; Benigno Sánchez; Juan M. Coronado (pp. 251-259).

Display Omitted► Hydrothermal parameters modulate morphology and photoactivity of titanate nanotubes. ► Shoddily defined nanotubes show higher photoactivity due to their larger S_BET. ► Increasing calcination temperature boosts the photoactivity of these materials. ► Nanotubes calcined at 300–350°C exhibit the highest conversion and selectivity. ► Titanate nanotubes present higher selectivity than reference photocatalyst Degussa P25.The aim of the present research is to determine the optimum hydrothermal synthesis procedure for using TiO₂-based one-dimensional materials as photocatalysts for air treatment applications, in order to enhance their mineralization capacity. The prepared samples were thoroughly characterized by means of TEM, N₂ adsorption–desorption isotherms, XRD and Raman spectroscopy. Trichloroethylene (TCE) was selected as a convenient model volatile organic compound (VOC) due to its elevated reactivity. In this study, it is described how the selection of the synthesis parameters (TiO₂ precursor, hydrothermal treatment conditions, washing procedure or calcination temperature) allows modulating the nanotubes physicochemical characteristics and, thus, photoactivity. The optimization process led to nanotubes with remarkable photocatalytic performance, with high TCE conversion and selectivity to CO₂, which can be favourably compared to that of the benchmark photocatalyst Degussa P25.

Keywords: Photocatalysis; Air treatment; Trichloroethylene; Titanate; Nanotubes; TiO; ₂; Hydrothermal synthesis; Photo-oxidation

One-pot hydrothermal synthesis of a hierarchical nanofungus-like anatase TiO₂ thin film for photocatalytic oxidation of bisphenol A by Jiawei Ng; Xiaoping Wang; Darren Delai Sun (pp. 260-272).

. A mesoporous, hierarchical nanofungus-like anatase thin film was synthesized via a facile one-pot hydrothermal synthesis and exhibited excellent photocatalytic efficiency, in comparison with a Degussa P25 coated film.Display Omitted► Unique anatase TiO₂ thin film with hierarchical nanofungus-like structure. ► Mesoporous, surface-fluorinated photocatalyst of high BET surface area (102.1m²/g). ► Enhanced photocatalytic degradation of BPA over P25 nanoparticulate film. ► Facile one-pot hydrothermal synthesis accentuates potential in engineering applications.This article reports the synthesis of an anatase thin film bearing a unique, hierarchical nanofungus-like structure. The nanostructures were directly grown from a Ti substrate via a facile, one-pot hydrothermal reaction, thus rendering ease of catalyst separation, recycle and reuse. High-resolution images of field emission scanning electron microscope (FESEM) indicated presence of small titania nanoparticulates of ca. 20nm on the nanoflakes, which constitute to the final overall nanofungus-like morphology. Hydrothermal duration-progressive FESEM images illustrated evolution of the nanofungus-structure and provided some evidence of the probable mechanism in obtaining the final nanostructure. The crystallographic phases and orientation of the photocatalyst were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nitrogen adsorption–desorption isotherm indicated that the as-prepared catalyst possessed a mesoporous structure and a Brunauer–Emmett–Teller (BET) surface area of 102.1m²/g. Greater light absorbance as shown from the UV–vis diffuse reflectance spectra, denoted enhanced light harvesting effects for UV penetration, possibly induced by inherent mesopores. Surface elemental analysis by means of X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) underlined purity of the titania sample with detected presence of only Ti and O in the sample. High resolution XPS scan of F 1s region revealed presence of fluoride ions adsorbed on the surface of TiO₂, which promoted etching and surface fluorination within the acidic hydrothermal environment. The photocatalyst exhibited efficient photocatalytic degradation of Bisphenol A (BPA) under UV-A irradiation, in comparison with a Degussa P25 TiO₂ coated film. The mechanism behind UV photocatalytic degradation of BPA over TiO₂ was elucidated using charge-trapping species as diagnostic tools and evidence have shown hydroxyl radicals (OH) to be the predominant active species in associated oxidation processes.

Keywords: Anatase; Hydrothermal; Mesoporous; Thin film; Photocatalysis

Removal of NO_x from air through cooperation of the TiO₂ photocatalyst and urea on activated carbon fiber at room temperature by Jin Miyawaki; Takaaki Shimohara; Noriaki Shirahama; Akinori Yasutake; Masaaki Yoshikawa; Isao Mochida; Seong-Ho Yoon (pp. 273-278).

NO conversion over TiO₂–urea/ACF mixture under UV irradiation at 50% RH.Display Omitted► NO was successfully removed into N₂ with reactions with TiO₂ and urea supported ACF. ► The produced NO₂ on TiO₂ was passed over urea to be continuously reduced into N₂. ► Humidity accelerated NO₂ desorption from TiO₂, not interfering NO conversion into N₂.Removal of atmospheric NO to harmless N₂ was successfully achieved through the continuous oxidation and reduction of NO into N₂ using pitch-based activated carbon fiber (ACF), in which TiO₂ and urea were co-supported. The combination of TiO₂ and urea on the ACF gave high oxidation and reduction of NO. The TiO₂ photocatalyst converted NO into NO₂, which was immediately passed over urea on the ACF and reduced into harmless N₂. Humidity seemed to accelerate the desorption of NO₂ from the TiO₂ surface, but did not affect the NO oxidation, indicating that humidity did not interfere with the reaction of NO into N₂. The ACF system described is potentially very useful for the harmless removal of NO in the atmosphere near the roadside of urban area using natural wind effectively.

Keywords: NO; _x; TiO; ₂; Photooxidation; Urea; Activated carbon fiber

High surface area Au/CeO₂ catalysts for low temperature formaldehyde oxidation by Hong-Fang Li; Na Zhang; Ping Chen; Meng-Fei Luo; Ji-Qing Lu (pp. 279-285).

Display Omitted► High surface area Au/CeO₂ catalysts are active for formaldehyde oxidation. ► Au⁺ and Au³⁺ species provide sites for HCHO adsorption to form formate intermediates. ► Au_xCe1−_xO2−_δ solid solution contains more oxygen vacancies for oxygen activation.Gold catalysts supported on high surface area CeO₂ were synthesized and tested for low temperature formaldehyde oxidation. It was found that the reactivity was greatly enhanced by increasing surface area of the support. Complete conversion of formaldehyde was obtained on a 3.0Au/CeO₂-270 catalyst with a surface area of 270m²g⁻¹ at 50°C, and a conversion of 92.3% was obtained at 37°C over the same catalyst, which made it promising for indoor formaldehyde removal. Detailed characterizations of the catalyst showed that the enhancement could be attributed to two factors. One was that Au species mainly in high oxidation states formed on the high surface area CeO₂ resulted in a high degree of HCHO adsorption, as revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy. The other was the high surface area CeO₂ provided more oxygen vacancies by the nano effect and the formation of Au_xCe1−_xO2−_δ solid solution as revealed by Raman spectroscopy, on which oxygen molecules could be transformed to active species for the reaction.

Keywords: Formaldehyde oxidation; Gold catalyst; CeO; ₂; High surface area; Au; _x; Ce; 1−; _x; O; 2−; _δ; solid solution

Novel urea assisted hydrothermal synthesis of hierarchical BiVO₄/Bi₂O₂CO₃ nanocomposites with enhanced visible-light photocatalytic activity by Puttaswamy Madhusudan; Jingrun Ran; Jun Zhang; Jiaguo Yu; Gang Liu (pp. 286-295).

Hierarchical BiVO₄/Bi₂O₂CO₃ nanocomposite photocatalysts, prepared by a urea-assisted hydrothermal approach, exhibit an enhanced photocatalytic activity for degradation of Rhodomine B aqueous solutions under visible-light irradiation.Display Omitted► Hierarchical BiVO₄/Bi₂O₂CO₃ nanocomposites with {001} reactive crystalline facets were synthesized by a urea-assisted hydrothermal approach. ► The urea concentration and reaction time play a crucial role in determining the morphology. ► BiVO₄/Bi₂O₂CO₃ nanocomposites show enhanced photocatalytic activity.A novel hydrothermal approach is developed for the first time to synthesize hierarchical BiVO₄/Bi₂O₂CO₃ nanocomposites with reactive crystalline facets using urea as a morphology mediator. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, N₂ absorption–desorption isotherms and UV–visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated towards degradation of Rhodomine B (RhB) by visible-light. Our results indicate that both physical parameters and associated photocatalytic activity of BiVO₄/Bi₂O₂CO₃ nanocomposites can be tuned by urea concentration and reaction time in the synthesis process. With increasing urea concentration, the specific surface area, pore volume and average pore size increase. Compared to BiVO₄ and Bi₂O₂CO₃ bulk counterpart, BiVO₄/Bi₂O₂CO₃ nanocomposites show enhanced photocatalytic degradation activity of RhB. The mechanisms for the formation of BiVO₄/Bi₂O₂CO₃ nanocomposites and enhanced photoreactivity are discussed.

Keywords: Hierarchical structures; BiVO; ₄; /Bi; ₂; O; ₂; CO; ₃; Nanosheet; Visible light; Photocatalysis

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Applied Catalysis B, Environmental (v.110, #)

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Applied Catalysis B, Environmental (v.110, #)