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.