Theoretical study on the mechanism of the hydrogen evolution reaction catalyzed by platinum subnanoclusters.

The smallest subnanocluster models of platinum colloid (Pt) are supposed to diffuse in aqueous media in order to examine their behaviors when they are subjected to the electrocatalytic hydrogen evolution reaction under zero overpotential conditions at pH 0. The DFT approach allows us to clarify the nature of individual proton transfer (PT) and electron transfer (ET) processes together with the importance of relying on concerted proton-electron transfer (CPET) pathways to promote the majority of H* adsorption processes by Pt subnanoclusters. Although the CPET processes are closely correlated with the Volmer steps (Pt + H + e → Pt-H*) described so far in electrochemistry, our study for the first time points out the essential capability of the Pt clusters to promote the multiple PT steps without the need to transfer any electrons, revealing the fundamentally high basicity of the naked Pt clusters (p = 27-28 for Pt, Pt, and Pt).