Edge sites dominate the hydrogen evolution reaction on platinum nanocatalysts

Platinum nanocatalysts facilitate the hydrogen evolution reaction (HER) for renewable chemical fuel generation. These nanostructures encompass diverse surface sites, including (111) and (100) facets and edge sites between them. Identifying the exact active sites is essential for optimal catalyst design, but remains challenging. Here, combining electrical transport spectroscopy (ETS) with reactive force field (ReaxFF) calculations, we profile hydrogen adsorption on platinum nanowires and reveal two distinct peaks: one at 0.20 VRHE for (111) and (100) facets and one at 0.038 VRHE for edge sites. Concurrent ETS and cyclic voltammetry show that edge site adsorption coincides with the onset of the HER, indicating the critical role of edge sites. ReaxFF molecular dynamics calculations confirm lower activation barriers for the HER at edge sites, with two to four orders of magnitude higher turnover frequencies. ETS in alkaline media reveals substantially suppressed hydrogen adsorption on edge sites, contributing to the more sluggish HER kinetics. These findings resolve the elusive role of different sites on platinum surfaces, offering critical insights for HER catalyst design. Pt is the most active catalyst for the hydrogen evolution reaction in acidic media, but the precise nature of its active sites remains elusive. Now electrical transport spectroscopy and molecular dynamics are combined to map the hydrogen adsorption sites on Pt nanowires and reveal the much higher activity of (111)/(100) edge sites.