First-Principles-Based Kinetic Monte Carlo Model of Hydrogen Evolution Reaction under Realistic Conditions: Solvent, Hydrogen Coverage and Electric Field Effects

The hydrogen evolution reaction (HER) plays an important role in electrocatalytic water splitting. Despite the progress on the development of HER catalysts, the dynamic evolution of HER reaction under realistic electrochemical conditions considering the electric field, solvent, and hydrogen coverage effects is still unclear. In this study, a first-principles-based H surface coverage and potential-dependent kinetic Monte Carlo (KMC) HER model on the Pt (111)/Pt (100) surface is presented. The reaction kinetics and electronic structure analysis of HER on Pt surfaces in the presence of dihydrated proton (H5O2+) and H surface coverage is investigated using density functional theory (DFT). The HER KMC model was developed based on the DFT-calculated energetics. The KMC simulation results showed that consideration of H5O2+ species and dynamic evolution of H coverage is essential for accurate description of HER reaction on the Pt catalyst, which fits well with HER polarization data. Moreover, sensitivity analysis shows that HER on Pt (111) is mainly affected by the Tafel step. On the Pt(100) surface, HER is primarily governed by the Heyrovsky pathway. Surface species evolution analysis demonstrates that the high working potential accelerated the formation of [Pt-2H] species, leading to increased H coverage and accelerating the HER process. The predicted weakened H binding strength and increased H coverage at high HER working potential was verified by in situ attenuated total reflection Fourier transformed infrared spectroscopy analysis. Overall, the proposed DFT-KMC model represents the state-of-art dynamic simulation of catalytic HER reaction, providing important insights into the evolution of HER under realistic operation conditions.