On the Activity of Platinum Catalysts in Solution. Part 2. Kinetics of the Pt-O Reaction with Hydrogen and of Pt-H Deposition Using a Double-Pulse Technique

摘要

Surface coverages of oxygen and hydrogen were determined on electrodes of differing activities as a function of time and voltage in the potential decay curve following an anodic pulse. The electrolyte was 1M H2SO4 containing dissolved hydrogen. No important difference, other than rate, is found in the way Pt-O is removed from surfaces of differing activity; however, a significant difference is noted in the way hydrogen resorbs. The rate of Pt-O removal is of apparent first order in adsorbed oxygen when the initial fraction of the surface covered is about 1.0; it is zero order in adsorbed oxygen and amount reacted when the initial surface coverage is less than 0.8. It is zero order in hydrogen partial pressure in both cases. The rate of the decay reaction is probably not limited by mass transport of solution H2 to the surface, by obstruction of active surface sites by sorbed product molecules, or by slow chemisorption of solution H2 on the electrode prior to reaction with Pt-O. (Author)