The hydrogen evolution reaction (HER)

Recent results collected within the corrosion group of the RMR department at the SCK CEN indicate that the cathodic current observed on steel in neutral and alkaline PWR water could increase with increasing pH. The question was raised whether we were still facing the hydrogen evolution reaction or we were confronted to another overall electrochemical reaction. Having reviewed some basic literature in the field, we conclude that an appropriate treatment of the mechanism related to the HER can possibly explain the experimental observations. Furthermore, we found literature data stressing the importance of the proton carrier involved in the mechanism. More specifically, we noted that boric acid or B-containing species could replace water for carrying protons to the electrode in alkaline media. We suggest examining carefully the kinetic mechanisms of the HER on steels, extending the scope of the experimental work to conditions that are closer to the ones prevailing in PWR reactors. The help of an in-house specialist in the field of spectroscopie techniques would be welcome.