Contamination of Metal Impurities during Hydrogen Evolution/Oxidation Reaction

Reliable and reproducible activity investigations on platinum provide a basis for fundamental understanding of kinetics and mechanism for hydrogen evolution/oxidation reaction (HER/HOR) in alkaline media. In this work, we studied the catalytic performance of polycrystalline Pt and HSAC-Pt in commonly used 0.1 M NaOH. Unexpectedly, we encountered difficulties in which an accumulation of impurities occurs during HER/HOR measurements in NaOH. For identifying the source of impurities, we systematically analyzed our electrochemical set-up like cell material, hydrogen gas, etc. Finally, X-ray photoelectron spectroscopy (XPS) data enable an improved identification of the observed impurities after HER/HOR. Thereby, we showed that traces of metal cations in the electrolyte solution can be deposited on the electrode surface during the HER and leads to catalyst poisoning. We suggest an electrochemical purification step to reduce these impurities from the electrolyte solution. The use of purified NaOH electrolyte solution provides reliable and reproducible studies for HER/HOR activity benchmarking of Pt-based catalysts in alkaline media.