Preparation of  WC  x Thin Films by RF Sputtering and Their Electrocatalytic Property for Anodic Methanol Oxidation

Thin films of W‐C compounds were prepared by RF sputtering and the electrocatalytic characteristics for anodic methanol oxidation were studied by taking into account their surface compositional and structural properties: ultrahigh vacuum (UHV) Auger electron spectroscopy system was combined with an RF sputtering apparatus so as to analyze the surface of sputtered films in the same vacuum without handling in the ambient atmosphere, thus avoiding surface contamination. Two kinds of films which were prepared from WC or W target by normal or reactive RF sputtering in Ar or mixed atmosphere were found to be electrocatalytically active toward the anodic methanol oxidation. Particularly, films containing the crystalline phase obtained by the normal RF sputtering of WC target or by the reactive RF sputtering of W target in the mixed atmosphere with concentration below 10 mole percent (m/o) provided only a poor activity or stability toward methanol oxidation, but amorphous films prepared by the reactive RF sputtering in the atmosphere of Ar containing of 10.0 m/o or above exhibited a platinum‐like electrocatalytic behavior with excellent stability as electrode materials.