In situ redox deposition of palladium nanoparticles on oxygen-deficient tungsten oxide as efficient hydrogenation catalysts

Abstract

Noble metal/metal oxide support hybrid materials have attracted tremendous interest due to their wide applications in catalysis. Herein, we have developed a novel and surfactant-free method to prepare Pd/WO_3−x composite materials with clean surfaces. Oxygen-vacancy-rich WO_3−x nanowires (NWs) provide free electrons to reduce Pd²⁺, and surface-clean Pd nanoparticles (NPs) directly grow on WO_3−x surfaces through an in situ redox reaction between reductive WO_3−x and metal salt precursor (Na₂PdCl₄) in aqueous solution. The as-obtained Pd/WO_3−x nanocomposites show excellent catalytic activities for the hydrogenation of 4-nitrophenol (4-NP) and styrene. The apparent rate constant for 4-NP reduction is 0.045 s⁻¹, over the Pd/WO_3−x catalyst. The turnover frequency (TOF) value for styrene hydrogenation is 1074.5 h⁻¹, thus, exhibiting high catalytic performance. Moreover, the obtained Pd/WO_3−x catalyst exhibits good stability. Oxygen vacancies in WO_3−x NWs can accelerate electron transport and promote hydrogen adsorption and dissociation on the surface of the catalyst. The strong interaction between Pd NPs and WO_3−x support contributes to the excellent performance. Our work provides a novel and simple strategy to directly fabricate other-noble metal NP loaded oxygen-deficient metal oxides as highly efficient catalysts for chemical transformation.