Understanding Water Structure and Hydrogen Association on Platinum-Electrolyte Interface

Platinum (Pt) is a benchmarked catalyst for several electro-catalytic processes, although the complex nature of heterogeneous charge transfer processes at the platinum-electrolyte interface hinders an atomistic level understanding of the electrodics. In this study, we aim to capture the chemical changes of Pt surfaces brought on by an applied potential, which can probe the catalytic efficacy under varying applied bias. Through a combined experimental and reactive molecular dynamics (MD) simulation approach, we uncover the effect of charge build up on the surface of the Pt electrode, which can be directed towards capacitive and faradaic processes. In the case of a moderately acidic pH shown here, the potential dependence of simulated electrodic processes align well with the experimental results from electrochemistry and in situ surface enhanced Raman spectroscopy (SERS). Using reactive MD and SERS based studies, we are able to probe into the interfacial water structure and the formation of the Helmholtz layer. At reductive potentials of ∼0.3-0.0 V vs RHE, we simulate phenomenon such as under potential hydrogen adsorption and hydrogen evolution/oxidation reaction. Together, the investigation establishes a framework for quantitative exploration of catalytic processes in electrolytes at very high spatial and temporal resolution.