Hydrogen evolution in aqueous solutions containing dissolved CO2 : Quantitative contribution of the buffering effect

The hydrogen evolution reaction (HER) occurring on steel in an oxygen-free aqueous solution containing dissolved CO2 was investigated. This reaction was modelled by taking into account the two dissociation reactions of dissolved CO2. The mathematical problem was solved numerically using a finite element method (FEM). A fair agreement between the measurements performed on a steel rotating disc electrode and the theoretical calculations was obtained. Thus, the cathodic behaviour of steel in CO2-containing solutions can be fully explained by the buffering effect induced by the presence of CO2. Some interfacial pH measurements performed on a gold electrode also support this conclusion.