Mechanism of interaction of molecular hydrogen with adsorbed oxygen on platinum electrodes under open circuit conditions

Transients of open-circuit potential observed at the reaction of hydrogen molecules with oxygen preliminarily adsorbed (O(ads)) on the smooth polycrystalline (pc Pt) and platinized platinum (Pt/Pt) electrodes are measured under conditions of controlled stirring of solution (0.5 M H(2) SO(4)). The dependence of the surface coverage with O(ads)(theta(O)) on the potential in the cause of the potential decay on pc Pt are determined. It is found that for Pt/Pt, the reaction kinetics is largely determined by diffusion of H(2). For pc Pt in the range of high theta(O), the Eley-Ridiel mechanism is realized. For medium theta(O), the regions where the reaction obeys the mechanisms of Eley-Ridiel, "conjugated reactions", and diffusion control are observed to overlap (even at the most intense stirring possible). The rate of H(2) reaction with O(ads) is substantially higher compared with analogous reactions of CO, HCOOH, and CH(3)OH.