Sonochemical synthesis of tungsten carbide–palladium nanocomposites and their electrocatalytic activity for hydrogen oxidation reaction

Nanocomposites between β-WC and Pd nanoparticles supported on carbon are synthesized and their electrocatalytic properties for the hydrogen oxidation reaction have been investigated. The Pd nanoparticles are obtained by a chemical reduction reaction of PdCl2 and the β-WC nanoparticles by a sonochemical decomposition of W(CO)6 on Pd-loaded carbon followed by heat-treatment. Depending on the relative amounts of W to Pd, the Pd nanoparticles can be reacted with W to form Pd–W alloy nanoparticles. The Pd–W alloy, whose composition is estimated to have W less than 18 at.% based on its lattice parameter, lost most of the catalytic activity of Pd. On the other hand, the nanocomposite between β-WC and pure Pd shows an enhanced activity compared with that of Pd nanoparticles alone. This enhancement can be explained with the H+-spill-over to β-WC.