Enhancement of electrocatalytic activity of platinum for hydrogen oxidation reaction by sonochemically synthesized WC1−x nanoparticles

Two types of composite materials composed of Pt and WC_1−x nanoparticles supported on multiwalled carbon nanotubes (MWNT) are synthesized and evaluated in terms of their electrochemical properties, especially for the hydrogen oxidation reaction (HOR). The Pt nanoparticles are prepared by reduction of H₂PtCl₆ with NaBH₄, and the WC_1−x nanoparticles by a sonochemical method with a W(CO)₆ precursor. One of the composites is synthesized by forming WC_1−x nanoparticles on Pt-loaded MWNT and the other by physically mixing Pt-loaded MWNT with WC_1−x-loaded MWNT. The sonochemical synthesis of WC_1−x on Pt-loaded MWNT forms WC_1−x preferentially on Pt nanoparticles, which makes intimate contact between WC_1−x and Pt nanoparticles. The cyclic voltammograms of these composite materials show evidences for H⁺-spill-over from Pt to WC_1−x, thereby increasing the electrochemically active surface area (ECA). The composite in which WC_1−x is deposited on Pt shows a remarkable increase in ECA probably because the intimate contact between WC_1−x and Pt enhances the H⁺-spill-over. These materials exhibit enhanced HOR characteristics with Pt-specific mass activities about twice that of pure Pt nanoparticles.