STRUCTURAL, MORPHOLOGICAL AND SURFACE-PROPERTIES AS A FUNCTION OF COMPOSITION OF RU-OXIDE ELECTRODES(TI+PT MIXED)

A systematic investigation of the structural, morphological and surfac e properties of thermally prepared Ru0.3Ti(0.7 - x)PtxO2 (0 less than or equal to x less than or equal to 0 7) electrodes was conducted by e x situ (SEM, EDX, XPS) and in situ (voltammetry and open circuit poten tial) techniques. Significant changes were observed on substituting Ti O2 for PtOx. The electrochemical surface area increased dramatically ( similar to 10 times) reaching a maximum at 40% PtOx (nominal). Ru surf ace enrichment was observed while Pt + Ru segregates as rectangular cr ystals from the coatings. At the higher Pt-contents, surface electroch emistry is mainly dominated by Pt solid-state transitions, especially after continuous potential cycling (0.4-1.4 V vs r.h.e.). Pt-containin g coatings were revealed to be unstable (erosion) when the cathodic sw itching potential, E-lambda,E-c,, was fixed at 0.4 V. Limiting En, to 0.9 V vs r.h.e, eliminates coating instability. Preferential Ru dissol ution, promoted by cathodic Pt dissolution, was revealed by ICPES. Wit h the exception of the 0-20% PtOx containing coatings, where evidence for the presence of Ru-VI was found, Ti and Ru are present in the +4 o xidation while the +2 oxidation state predominates for Pt. (C) 1998 El sevier Science Ltd. All rights reserved.