A potential and pH inclusive microkinetic model for hydrogen reactions on Pt surface

The Pt surface-based hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) are the two most basic electrochemical reactions. However, an accurate quantitative microkinetic model of HER and HOR on Pt surface is still missing. In the current work, the charge transfer coefficient and potential-dependent reaction barriers are obtained via grand canonical fixed-potential calculations to predict such polarization curves. Excellent agreements between the prediction and experiments have been obtained. We found that the common practice of relating a Tafel slope to one specific prominent reaction channel is not reliable. Instead, the balance of several pathways might determine the Tafel slope. Our work demonstrated the important roles of the fixed-potential approach, the explicit water layer structure, and the cations in predicting the Pt-HER/ HOR accurately. The proposed computational framework can be generally applied to other electrochemical processes.

Automated summary

This study utilized grand canonical fixed-potential calculations to obtain the charge transfer coefficient and potential-dependent reaction barriers, successfully predicting the polarization curves of hydrogen evolution reaction and hydrogen oxidation reaction. It demonstrated the unreliable correlation between Tafel slope and a specific reaction channel. The results highlighted the significant roles of the fixed-potential approach, explicit water layer structure, and cations in accurately predicting the Pt surface reactions.