Cyclic voltammetry and X-ray photoelectron spectroscopy studies of electrochemical stability of clean and Pt-modified tungsten and molybdenum carbide (WC and Mo_2C) electrocatalysts

摘要

The electrochemical stability of tungsten carbide (WC), Pt-modified WC, molybdenum carbide (Mo_2C), and Pt-modified Mo_2C has been examined using an in situ electrochemical half-cell in combination with X-ray photoelectron spectroscopy (XPS). The WC surface, created via the carburization of a tungsten foil, was electrochemically stable to ～0.8 V with respect to the normal hydrogen electrode (NHE) when exposed to dilute sulfuric acid. At higher potentials, XPS confirmed the surface oxidation of WC to form W_xO_y species. The deposition of submonolayer coverage of Pt on the WC surface increased the region of stability of WC, extending the onset of catalyst oxidation to ～1.0 V (NHE). These results suggest that both WC and Pt/WC have the potential to be used as anode electrocatalysts. In contrast, both Mo_2C and Pt-modified Mo_2C underwent oxidation at ～0.4V (NHE), indicating that molybdenum carbides are not stable enough for applications as anode electrocatalysts.