Theoretical description of the kinetics of proton adsorption at the oxide/electrolyte interface based on the statistical rate theory of interfacial transport and the 1pK model of surface charging

A new approach describing ion adsorption kinetics on metal oxide surfaces from electrolyte solution is presented. It was assumed that the diffusion of ions to the oxide surface is fast, and the kinetics of ion adsorption is controlled by the transition of ions from the bulk to the adsorbed state. The transition rate is considered in terms of the statistical rate theory (SRT) of interfacial transport. To simplify the theoretical considerations, the simple Gouy-Chapman model of the electric double layer is applied together with the 1pK protonation model. The above theoretical approach was used to analyze the rate of proton adsorption. Additionally, that kinetic model was applied to study the hysteresis of potentiometric titration curves and the heat of proton adsorption (i.e., difference in the measured quantity at a given pH from acid and base titration). According to the SRT approach, the rate of hydrogen ion adsorption strongly depends on pH, which has a significant influence on numerically simulated titration curves and the heat of proton adsorption.