Coupled Palladium-Tungsten Bimetallic Nanosheets/TiO2 Hybrids with Enhanced Catalytic Activity and Stability for the Oxidative Removal of Benzene.

Since the conventional Pd-based catalysts often suffer severe deactivation by water, development of a catalyst with good activity and moisture-resistance ability is of importance in effectively controlling emissions of volatile organic compounds (VOCs). Herein, we report the efficient synthesis of ultrathin palladium-tungsten bimetallic nanosheets with exceptionally high dispersion of tungsten species. The supported catalyst (TiO2/PdW) shows good performance for benzene oxidation, and 90% conversion is achieved at a temperature of 200 °C and a space velocity of 40 000 mL g-1 h-1. The TiO2/PdW catalyst also exhibits better water-tolerant ability than the traditional Pd/TiO2 catalyst. The high catalytic efficiency can be explained by the facile redox cycle of the active Pd2+/Pd0 couple in the close-contact PdO x-WO x-TiO2 arrangement. We propose that the reason for good tolerance to water is that the lattice oxygen of the TiO2/PdW catalyst can effectively replenish the oxygen in active PdO x sites consumed by benzene oxidation. A four-step benzene transformation mechanism promoted by the catalyst is proposed. The present work provides a useful idea for the rational design of efficient bimetallic catalysts for the removal of VOCs under the high humidity conditions.

Au-Pd/mesoporous Fe2O3: Highly active photocatalysts for the visible-light-driven degradation of acetone.

Three-dimensionally ordered mesoporous Fe2O3 (meso-Fe2O3) and its supported Au, Pd, and Au-Pd alloy (xAuPdy/meso-Fe2O3; x=0.08-0.72wt.%; Pd/Au molar ratio (y)=1.48-1.85) photocatalysts have been prepared via the KIT-6-templating and polyvinyl alcohol-protected reduction routes, respectively. Physical properties of the samples were characterized, and their photocatalytic activities were evaluated for the photocatalytic oxidation of acetone in the presence of a small amount of H2O2 under visible-light illumination. It was found that the meso-Fe2O3 was rhombohedral in crystal structure. The as-obtained samples displayed a high surface area of 111.0-140.8m2/g and a bandgap energy of 1.98-2.12eV. The Au, Pd and/or Au-Pd alloy nanoparticles (NPs) with a size of 3-4nm were uniformly dispersed on the surface of the meso-Fe2O3 support. The 0.72wt.% AuPd1.48/meso-Fe2O3 sample performed the best in the presence of 0.06mol/L H2O2 aqueous solution, showing a 100% acetone conversion within 4hr of visible-light illumination. It was concluded that the good performance of 0.72wt.% AuPd1.48/meso-Fe2O3 for photocatalytic acetone oxidation was associated with its ordered mesoporous structure, high adsorbed oxygen species concentration, plasmonic resonance effect between AuPd1.48 NPs and meso-Fe2O3, and effective separation of the photogenerated charge carriers. In addition, the introduction of H2O2 and the involvement of the photo-Fenton process also played important roles in enhancing the photocatalytic activity of 0.72wt.% AuPd1.48/meso-Fe2O3.

Carbon Monoxide Oxidation over rGO-Mediated Gold/Cobalt Oxide Catalysts with Strong Metal-Support Interaction.

The strong interaction between Au nanoparticles and support (Au-metal oxide interface) usually governs the performance of a supported Au catalyst in heterogeneous catalysis. In this study, a series of Au/reduced graphene oxide (rGO)/three-dimensionally ordered macroporous (3DOM) Co3O4 catalysts with similar textural properties were prepared using the poly(methyl methacrylate)-templating and poly(vinyl alcohol)-protected reduction strategies. It was found that introducing reduced graphene oxide (rGO) as an electron-transfer bridge between Au and 3DOM Co3O4 could significantly strengthen the strong metal-support interaction (SMSI), thus enhancing the catalytic activity for CO oxidation. Among all of the catalysts, 1.86 wt % Au/2 wt % rGO/3DOM Co3O4 (1.86Au/2rGO/3DOM Co3O4) showed the highest catalytic activity: the CO reaction rate at 40 °C (432.8 µmol/(gAu s)) was 2 times higher than that (208.2 µmol/(gAu s)) over 1.87Au/3DOM Co3O4. The introduction of rGO could improve the activation of oxygen molecules and hence increase the low-temperature catalytic activity. The strategy for strengthening the SMSI via rGO mediation would guide the designing of highly efficient supported metal catalysts for low-temperature oxidation of CO.