Specific features of interaction between formic acid and oxygen adsorbed on smooth polycrystalline platinum: Transients of the open-circuit potential

Transients of the open-circuit potential, which are observed when formic acid is interacting with adsorbed oxygen (O-ads) preliminarily accumulated on polycrystalline "smooth" platinum (pcPt), are measured in an aqueous solution of sulfuric acid. It is shown that, as with platinized platinum (Pt/Pt), at large coverages by adsorbed oxygen (theta O = 1-0.8), adsorbed oxygen interacts directly with molecules of formic acid from solution. In the region of medium coverages (theta(O) = 0.8-0.2), on the other hand, a mechanism of "conjugated reactions" is realized. It is established that, in the case of pcPt, the direct interaction of O-ads with molecules of HCOOH from solution proceeds slower by nearly three times and the interaction via the mechanism of "conjugated reactions," faster by about three times, as compared with Pt/Pt.