PREPARATION OF WCX 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 WCx films in the same vacuum without handling in the ambient atmosphere, thus avoiding surface contamination. Two kinds of WCx films which were prepared from WC or W target by normal or reactive RF sputtering in Ar or Ar-CH4 mixed atmosphere were found to be electrocatalytically active toward the anodic methanol oxidation. Particularly, films containing the crystalline WC1−δ phase obtained by the normal RF sputtering of WC target or by the reactive RF sputtering of W target in the Ar-CH4 mixed atmosphere with CH4 concentration below 10 mole percent (m/o) provided only a poor activity or stability toward methanol oxidation, but amorphous a-WCx films prepared by the reactive RF sputtering in the atmosphere of Ar containing CH4 of 10.0 m/o or above exhibited a platinum-like electrocatalytic behavior with excellent stability as electrode materials. © 1990, The Electrochemical Society, Inc. All rights reserved.