Effect of Titanium Dioxide Supports on the Activity of Pt-Ru toward Electrochemical Oxidation of Methanol

Abstract

TiO(2) and Nb-TiO(2) were investigated as stable supports for Pt-Ru electrocatalysts towards methanol oxidation. X-ray photo-electron spectroscopy (XPS) data for all these TiO(2)-based supports show oxidation states of Ti(4+), with no Ti(3+), suggesting low electronic conductivity. However, the deposition of metal nanoparticles onto the supports at loadings of 60 wt% metal dramatically increased conductivity, making these electrodes (metal particles + support) suitable for electrochemistry even though the supports have low conductivity. For some of these TiO(2)-based supports, the activity of Pt-Ru towards methanol oxidation was excellent, even surpassing the activity of the same electrocatalysts supported on carbon. The activity of the electrocatalyst depended on TiO(2) crystalline structure, the addition of Nb into the support and the weight loading of metal. For example, using anatase Nb-TiO(2) as a support increased the electrochemical activity of Pt-Ru by 83% compared to the same electrocatalysts supported on either carbon Vulcan XC-72R or rutile Nb-TiO(2). This electrode was also 64% more active than the one that had anatase TiO(2) as the support with no Nb. Finally, increasing the weight loading of metal from 5 to 60% increased the conductivity by 5 orders of magnitude and the activity by a factor of 20. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3559495] All rights reserved.