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 (Oads) on the smooth polycrystalline (pc Pt) and platinized platinum (Pt/Pt) electrodes are measured under conditions of controlled stirring of solution (0.5 M H2 SO4). The dependence of the surface coverage with Oads(θO) 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 H2. For pc Pt in the range of high θO, the Eley-Ridiel mechanism is realized. For medium θO, 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 H2 reaction with Oads is substantially higher compared with analogous reactions of CO, HCOOH, and CH3OH.