Fundamental Aspects of Contamination during the Hydrogen Evolution/Oxidation Reaction in Alkaline Media

Abstract

This work discusses the experimental pitfalls and challenges for activity benchmarking of hydrogen evolution/oxidation reactions (HER/HOR) for Pt-based catalysts in alkaline media. For identifying the source of impurities, we systematically analyzed our electrochemical set-up like cell material, hydrogen gas, and electrolyte solutions. Commonly used 0.1 M electrolyte solutions like LiOH, NaOH, and KOH were tested. We could mainly eliminate the glass cell and hydrogen gas as a main source of contamination for poly-Pt during HER/HOR in alkaline media. Long-term chronoamperometric experiments in different electrolyte solutions were applied to accumulate the impurities at the electrode surface. X-ray photoelectron spectroscopy (XPS) data enable clear identification of the observed contamination after HER/HOR. Thereby, we showed that traces of metal cations in the electrolyte solution can be electro-deposited on the electrode surface during HER and leads to strong catalyst poisoning. We have developed an electrochemical purification step to reduce these impurities stemmed from the electrolyte solution. The use of purified electrolyte solutions provides reliable and reproducible studies for HER/HOR activity benchmarking of Pt-based catalysts which is essential to underderstand HER/HOR kinetics and mechanism in alkaline media.