Structural, morphological and surface properties as a function of composition of Ru+Ti+Pt mixed-oxide electrodes

A systematic investigation of the structural, morphological and surface 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 ex situ (SEM, EDX, XPS) and in situ (voltammetry and open circuit potential) techniques. Significant changes were observed on substituting TiO2 for PtOx. The electrochemical surface area increased dramatically (similar to 10 times) reaching a maximum at 40% PtOx (nominal). Ru surface enrichment was observed while Pt + Ru segregates as rectangular crystals from the coatings. At the higher Pt-contents, surface electrochemistry is mainly dominated by Pt solid-state transitions, especially after continuous potential cycling (0.4-1.4 V vs r.h.e.). Pt-containing coatings were revealed to be unstable (erosion) when the cathodic switching 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 dissolution, promoted by cathodic Pt dissolution, was revealed by ICPES. With 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 oxidation while the +2 oxidation state predominates for Pt. (C) 1998 Elsevier Science Ltd. All rights reserved.