Mixed conducting catalyst support materials for the direct methanol fuel cell

Finely dispersed Pt- and Pt/Ru-particles have been deposited on high surface-area ruthenium dioxide (RuO2) using the Petrow and Allen method [U.S. Patent No. 4,044,193 (23 August 1977)]. RuO2 has been synthesized according to different preparation methods. It turned out that the product showing the highest surface area could be produced by a simple fast precipitation method. The electrocatalytic activities of catalysts on different ruthenium oxide supports have been investigated in half-cell experiments by stationary current voltage measurements. Pt/Ru-catalysts deposited on a Vulcan XC-72 carbon black have been used for comparison. X-ray analysis methods (XRD, EDX) have been used to characterize the composition and crystallinity of the materials and their geometric surface areas have been determined by the BET method. It turned out that the electric conductivity of the RuO2 materials was comparable to that observed for Vulcan XC-72. Furthermore, RuO2 materials having a BET surface area above 125 m2/g could be synthesized. (Vulcan XC-71: not, vert, similar250 m2/g). Surprisingly, no significant electrochemical activity was found when Pt/Ru was deposited on freshly precipitated hydrous RuO2. Deposition of noble metals on calcined RuO2 resulted in electrochemical activities comparable to the ones obtained for the Vulcan XC-72 support. Thus, no extraordinary enhancement of catalytic activity for the methanol has been observed when RuO2 oxide was used as a mixed conducting catalyst support.