Different Routes in the Forward and Backward Occurrences of the Hydrogen Electrode Reaction on Pt Single Crystal Electrodes in Acid Solution

Abstract

Abstract The hydrogen evolution and ionization reactions were studied on Pt single crystal electrodes in N2 or H2 saturated, acidic solutions. The hydrogen evolution reaction was structure insensitive and the ionization reaction was structure dependent. The Tafel constants of the respective reactions, and , and the reaction orders, and , with respect to proton, did not satisfy the relationships, + = 2 and − = −2, deduced by the rate-determining step which is the same for the hydrogen evolution and ionization reactions; The results were, + ≈ 4 and − ≈ −4. These suggest that the rate-determining steps is different for the evolution and ionization reactions in acidic solutions. A tentative model for the reaction routes was proposed.