Effect of Hydrogen Pressure on the Intrinsic Kinetics of Hydrogen Evolution Reaction at Pt(111) Electrode

Abstract

Many kinetic studies on hydrogen evolution reaction (HER) were done in N2 saturated solutions in order to avoid possible H2 leakage, which results in a variation of H2 concentration at the electrode/electrolyte interface ( c H 2 s ). It will induce the drift of equilibrium potential (Eeq) and applied activation overpotential (η act) for HER. Consequently, it may result in errors for estimating the kinetic parameters for HER. By taking HER at Pt(111) under RDE configuration as a model reaction, quantitative relation among c H 2 s and the reaction current density (j) is established based on the mass transport equations. From the j–η act plots, our results reveal that i) with the increase of HER current, the equivalent c H 2 s increases, which accompanies with a drift of thermodynamic equilibrium potential (Eeq) for HER decreases; ii) when η act is negative of −50 mV, the j–η act plot for HER is the same in N2 and H2 saturated solution, with a slope of 30 mV Dec−1; Our results suggest that HER activity should be compared in solutions with the same composition and at the same activation overpotential instead of at the same applied potential. Proper experimental methods for post data analysis are proposed in order to derive the intrinsic HER kinetics.