In search for non precious metal oxide electrodes with the case of BaMoO₃ thin films for hydrogen evolution reaction

Non-precious metal oxides are inexpensive catalysts for hydrogen evolution reaction (HER) in water electrolysis to realize the global-scale green hydrogen production. Here, we report on perovskite BaMoO₃ thin films fabricated by pulsed laser deposition. The metallic films, grown on single crystalline NdGaO₃ substrates, have the expected stoichiometry, are crystalline, and epitaxially grown in (001) direction. Relatively low electrochemical activity is found and the thin films rapidly degrade under HER conditions, contrary to expectations from the literature. Our research highlights that the processing conditions and the processing related properties of a material can have considerable effect not only on the activity, but also on the stability. In particular, stability assessment is key in identifying promising, alternative HER catalysts. In search for alternative materials, degradation needs to be investigated from the very first and specifically include catalyst characterization after electrochemical aging experiments. Attention must be paid to investigate the intrinsic properties of a material, to be aware of processing related properties of a catalyst, and to complement the performance analysis with detailed materials characterization.