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Abstract:
Despite much study the mechanism of the hydrogen evolution reaction (HER) on Pt is still controversial. Part of the challenge is that any comprehensive description may have to describe processes on timescales from the femtosecond, interfacial electron transfer, to millisecond, ion diffusion. Here we separate these timescales using a femtosecond perturbation approach: we collect cyclic voltammograms from several Pt electrodes with and without femtosecond laser irradiation. We find that at biases near hydrogen evolution laser irradiation lowers the barrier for H2 generation, while in the H under potential deposition range it induces partial charge transfer along the Pt‐H bond and interfacial dipole (re)arrangement. The trend in ultrafast partial charge transfer we measure, Pt(111) < Pt(100) < Pt(110) << Pt microelectrode, is the same as for H2 generation suggesting insight into both ultrafast electron transfer and slow double layer structural change is required to describe HER mechanism.
