Hydrogen Uptake Kinetics of Cathodic Polarized Metals in Aqueous Electrolytes

We use a unique combination of electrochemical techniques to elucidate thedependency of hydrogen evolution reaction (HER) and absorption on pH andoverpotential for iron and nickel. Impedance spectroscopy shows the dominanceof the Volmer-Heyrovsky reaction pathway, challenging the common considerationof Volmer-Tafel dominance. Polarization slopes agree with the Volmer orHeyrovsky rate-determining step, with limitations at high overpotential. Theevolution of steady-state permeation current density with overpotential isrationalised through newly-developed theory. Surface activity and absorptiontrends are captured. Combined with modelling, this work provides a path forquantifying hydrogen uptake and establishing an equivalent fugacity for aqueouselectrolytes.