KINETICS OF HYDROGEN EVOLUTION REACTION ON BRIGHT PLATINUM-ELECTRODE IN AQUEOUS DIMETHYLFORMAMIDE SOLUTIONS BY CYCLIC VOLTAMMETRY

Kinetic behaviour of hydrogen evolution reaction (HER) has been studied on bright platinum electrode in aqueous mixtures of 0, 25, 50, 75, 90 and 100 wt% N,N-dimethylformamide (DMF) from both HCl and HClO4 solutions by cyclic voltammetry under varying sweep rates [500-1 mVs-1] in the cathodic potential region of 0-1000 mV. The cyclic voltammograms are characterized by single cathodic and the corresponding anodic peaks and are found to be quasi-reversible in nature. The relevant kinetic parameters like the diffusion coefficient (D(R)) of the reductant and the rate constant (k(s)) (based on apparent area of the electrode) have been derived using the formulations of Shain and Nicholson. The values of D(R) and k(s) in aq. DMF mixtures decrease from that in pure water due to possible increased protophilicity of DMF-water mixtures which hinders the solvated H+ ions to approach the electrode surface for undergoing HER.