Suppressed Hydrogen Peroxide Generation and Enhanced Electrochemical Hydrogen Oxidation Activity for Tungsten-Oxide-Modified Platinum Surface Model Catalyst System

Suppressed hydrogen peroxide (H2O2) generation and practical H2 oxidation reaction (HOR) activity of the anode catalyst surface is crucial to improve proton exchange membrane fuel cells (PEMFCs) performance. Here, the influence of surface modification on H2O2 generation and HOR activity by introducing tungsten suboxides (WOx) was investigated for platinum catalyst surfaces. A Pt(111) single-crystal substrate surface was used as the model of Pt-nanoparticle anode catalyst surface and modified with WOx through the reactive arc plasma deposition (APD) of W under an O2 partial pressure (p(O2) = 1 × 10−1 or 10−3 Pa). The oxidation states of WOx were estimated by X-ray photoelectron spectroscopy, and the resulting electrocatalytic properties of H2O2 generation and HOR activity were investigated using a scanning electrochemical microscope. The as-prepared oxidation states of WOx were modified depending on p(O2) during the APD. Contrarily, potential cycle (PC) loadings resulted in a similar oxidation state of WOx: substoichiometric oxides containing W4+ or W5+, irrespective of the as-prepared oxidation states of the deposited tungsten. Regardless of the WOx oxidation state, the WOx/Pt(111) surfaces exhibited suppressed H2O2 generation, even accompanied by enhanced HOR activity compared with the clean Pt(111). Therefore, the WOx surface modification can improve the properties of Pt-based anode catalysts and contribute to high-performance catalyst developments.