Electrocatalytic Behavior of Pt/WO3 Composite Layers Formed Potentiodynamically on Tungsten Surfaces

The Pt/WO3 composites, in a form of thin layer on W support, were prepared by potentiodynamic polarization of either bare or oxide covered tungsten disc in hexachloroplatinic acid solutions. Both the Pt loading and the thickness of WO3 interlayer between Pt nanoparticles and W metal surface were varied. The chemical and electrochemical stability tests in 0.1 mol dm(-3) HCIO4 solution were performed by cyclic voltammetry. These test revealed that the shape of cyclovoltammetric curves displayed relatively slight dependence on the number of cycles. The shape changes were attributed to a slight redistribution of WO3 over the composite surface. Tracking for the synergistic effects in the Pt/WO3 system, the influence of both WO3 thickness and Pt loading on the kinetics of both hydrogen evolution/oxidation (HER/HOR) and oxygen reduction reactions (ORR) in acidic solution were investigated. The kinetics of HER was found to be a) independent on the WO3 thickness, and b) inversely proportional to the Pt loading. For ORR we found that the onset potential, approaching thermodynamic limit of 1.23 V vs. RHE, was almost independent on oxide thickness, while the reaction kinetics was commensurable to the Pt loading.