LPS current peaks arising from hydrogen evolution involving proton donors

Abstract

Linear potential sweep (LPS) voltammetry was applied to study hydrogen evolution in the systems containing acetic or gluconic acid as proton donors. LPS voltammograms display well-defined current peaks (ip) that vary linearly with √–υ (υ is a potential sweep rate). According to the model, developed for the CE (chemical step + electrochemical step) mechanism and accounting for kinetics of chemical interactions in the diffusion layer, current peaks depend on the total concentration of proton donors and acceptors (cH). This conclusion is in line with linear dependences between ∂ip / ∂√–υ and cH, observed experimentally in both systems. At least two factors seem to be responsible for diminution of current peaks in gluconate system. The first of them is related to a lower diffusion coefficient of gluconate; the second factor derives from notably slower kinetic steps involving formation or dissociation of gluconic acid.