Surface treatment effects on the electrocatalytic activity and characterization of intermetallic phases

Ordered intermetallic phases of PtBi and PtPb have been prepared and studied [using cyclic voltammetry, rotating disk electrode voltammetry, and Fourier transform infrared (FTIR)] as potential fuel cell electrocatalysts using formic acid as a model system, elucidating electrochemical activity, reaction kinetics, and resistance to CO surface poisoning. Both electrodes displayed activity superior to that of pure Pt under any conditions tested but were found to roughen at significantly positive potentials (typically above +400 mV vs. Ag/AgCl) in acidic media, likely due to preferential dissolution of the p-block metal (Bi, Pb). Each electrode was subjected to a variety of surface treatments to obtain suitable cleaning methods. Mechanical polishing with alumina was found to be the best treatment for PtBi, while PtPb was fairly insensitive to treatment procedures and parameters. Using the rotating disk electrode method, a value of 1.4 x 10(-4) cm s(-1) was obtained for the heterogeneous charge-transfer rate constant for PtPb in formic acid. Both PtBi and PtPb exhibited high tolerance to CO poisoning; no evidence of CO adsorption at any potential was found via FTIR. (C) 2004 The Electrochemical Society.