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Abstract: Three polymorphs of Ga2O3 (α-, β-, and γ-Ga2O3) were prepared, and their photocatalytic activities were evaluated by the decomposition of volatile aromatic compounds (e.g., benzene, toluene, and ethylbenzene) in dry air stream under UV light illumination at room temperature. It was found that the Ga2O3 catalysts exhibited much higher photocatalytic activity than commercial TiO2. The photocatalytic activities of the Ga2O3 polymorphs were strongly influenced by their crystal structure, and their specific activities decreased in the following order: β-Ga2O3 > α-Ga2O3 > γ-Ga2O3. The reasons for the differences in photocatalytic activity of the Ga2O3 polymorphs are discussed in terms of crystallinity, geometric structure, and electronic properties of the polymorphs. [Copyright &y& Elsevier]

Efficient visible-light-driven selective oxidation of benzyl alcohol to benzaldehyde over Pt/5MnNS. [Display omitted] • Multicomponent Pt/Mn-Bi 4 Ti 3 O 12 ultrathin nanosheets were successfully constructed. • Pt/5MnNS exhibited high benzaldehyde yield rate (1180 μmol·g−1·h−1). • Surface Ti4+δ sites as stronger Lewis acid sites effectively activated benzyl alcohol. • The structure–function relationship for the multicomponent Pt/5MnNS was revealed. Herein, a series of Pt nanoparticles modificatory Mn doped Bi 4 Ti 3 O 12 ultrathin nanosheets (Pt/MnNS) are constructed as a surface functionalized photocatalyst for the visible-light-driven selective benzyl alcohol (BA) oxidation. Especially, Pt/5MnNS shows the best performance with a benzaldehyde (BD) yield rate of 1180 μmol·g−1·h−1 and a selectivity of 99.9 %. More importantly, experimental results reveal that Mn doping not only extends the optical absorption range of the photocatalyst to the visible region, but also induces the formation of more surface Ti4+δ atoms. Those Ti4+δ atoms as stronger Lewis acid centers achieve more conspicuous adsorption and activation of BA via the C O⋯Ti coordination. It makes the deprotonation of BA by photogenerated holes be easier. Meanwhile, Pt nanoparticles significantly promote the separation and transfer of the photogenerated carriers for supporting the formation of superoxide and carbon-centered radicals. Thus, the photocatalytic BA oxidation efficiency is markedly improved by surface multicomponent synergistic effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nickel disulfide decorated CdS nanosheets (NiS 2 /CdS) are synthesized. • NiS 2 can serve as the active sites for hydrogen evolution reaction and dehydrogenation reaction. • The integrated photocatalytic redox cycles for H 2 production and imine synthesis are achieved on NiS 2 /CdS. Photocatalytic hydrogen (H 2) evolution integrated with selective oxidation to produce fine chemicals is a promising strategy for solar energy conversion and storage; however, the efficiency of such coupled photocatalytic redox cycles is greatly limited by the poor surface kinetics of hydrogen evolution reaction (HER) and/or dehydrogenation reaction (DHR) on heterogenous photocatalysts. Herein, we demonstrate that the immobilization of ultrafine nickel disulfide (NiS 2) nanoparticles on CdS nanosheets (NiS 2 /CdS) is a simple yet efficient approach to kinetic improve the surface redox reactions for H 2 production and dehydrogenative coupling of amines to imines. The NiS 2 nanoparticles loaded on CdS not only function as the HER active sites to speed up charge separation and to boost H 2 release, but also enhance the adsorption of amines to facilitate the dissociation of C-H and N-H bonds to form aldimines intermediates, which are readily coupled with other amines to afford a high selectivity toward imine synthesis. Benefiting from such unique bifunctional catalytic behavior of NiS 2 in proton (H+) reduction and substrate activation, NiS 2 /CdS exhibits a remarkable enhanced photocatalytic performance toward simultaneous production of H 2 and imines. The apparent quantum efficiency (AQE) at 420 nm is calculated to be 54.7%. This strategy using bifunctional cocatalysts to kinetic improve the surface redox reactions will have broad implications in the development of high-performance photocatalysts for integrated production of solar hydrogen and value-added solar chemicals. [ABSTRACT FROM AUTHOR]

The multifunctional photocatalysts (Au-Pd/SnNb 2 O 6 ultrathin nanosheets) are developed for selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde under visible light. The superior catalytic performance is attributed to a synergistic effect of Au, Pd nanoparticles, and SnNb 2 O 6 ultrathin nanosheets. [Display omitted] • Au-Pd/SnNb 2 O 6 (SN) as photocatalysts for selective hydrogenation of cinnamaldehyde. • The C = C of cinnamaldehyde would be absorbed on the surface Lewis acid sites of SN. • Photogenerated electrons promoted H 2 dissociation on Pd, Au reduced overhydrogenation. • The superior performance is attributed to a synergistic effect of catalyst component. Au-Pd bimetallic nanoparticles (NPs) supported on SnNb 2 O 6 ultrathin nanosheets (SN) were developed as multifunctional photocatalysts for the selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) under visible light irradiation. A representative catalyst (Au 6 -Pd 1 /SN) exhibits optimum performances with 99.8% conversion and 91.0% selectivity. The structure and surface properties of the prepared samples were revealed by SEM, TEM, BET, TPD, XPS, and EPR. The results of in situ FTIR spectra and NH 3 -TPD reveal that the rich surface Lewis acid sites on SN can chemisorb and activate CAL via the C = C...Nb coordination. EPR experiments indicate that H 2 would dissociate to activated H atoms on Pd NPs following a photopromoted surface catalytic process. Experimental results suggest that Au NPs reduce the over hydrogenation of HCAL by inhibiting the formation of Pd-H species. The superior catalytic performance is attributed to a synergistic effect of Au, Pd NPs and SN. Finally, a possible synergetic mechanism for Au-Pd/SN is proposed to illustrate the photocatalytic process. This work offers a reference to guide a novel and more effective photocatalyst design for precise organic synthesis driven by sunlight. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline PbBi2Nb2O9 was successfully prepared by a modified sol–gel method. The as-prepared nanocrystalline PbBi2Nb2O9 was an active visible-light-driven photocatalyst for the photoreduction of 4-nitroaniline to p-phenylenediamine in aqueous solution upon purging with N2. Its photocatalytic activity was determined by the balance between the surface area and crystallinity. The best sample was obtained after calcination at 650°C, giving 4-nitroaniline conversion of ∼100% and p-phenylenediamine selectivity of ∼99% after irradiation for 150min, which was much higher than those of bulk PbBi2Nb2O9 and TiO2− x N x photocatalysts. Further experiments revealed that oxalate anion (as a hole scavenger) was indispensable for the photocatalytic reduction of 4-nitroaniline. Moreover, on the basis of the electron spin resonance analysis result, a mechanism was proposed to explain the photoreduction of 4-nitroaniline over nanocrystalline PbBi2Nb2O9. [Copyright &y& Elsevier]

Postnitridation annealing has a remarkable effect on the surface property and photocatalytic performance of N-doped TiO2 for photocatalytic oxidation of ethylene. The activity of N-doped TiO2 under visible light illumination () can be enhanced fourfold by annealing the sample at 400 °C. Characterization results show that the thermal annealing reduces surface oxygen vacancies, removes surface-adsorbed NH3, and facilitates the adsorption of molecular oxygen on catalyst surface. Such a surface reconstruction contributes to the enhanced photocatalytic activity of the N-doped TiO2. The postcalcination also improves the photocatalytic stability of the N-doped TiO2 by stabilizing nitrogen atoms in the TiO2 lattice. A N-doped TiO2 sample without postcalcination suffers from a gradual deactivation, due mainly to the passivation of the catalyst surface by oxidized nitrogen species (e.g., hyponitrite, nitrite ions, and nitrate ions) formed during the photocatalytic degradation of ethylene. [Copyright &y& Elsevier]