The role of proton dynamics on the catalyst-electrolyte interface in the oxygen evolution reaction

The development of non-precious metal catalysts that facilitate the oxygen evolution reaction (OER) is important for the widespread application of hydrogen production by water splitting. Various perovskite oxides have been employed as active OER catalysts, however, the underlying mechanism that occurs at the catalyst-electrolyte interface is still not well understood, prohibiting the design and preparation of advanced OER catalysts. Here, we report a systematic investigation into the effect of proton dynamics on the catalyst-electrolyte interfaces of four perovskite catalysts: La0.5Sr0.5CoO3-δ (LSCO), LaCoO3, LaFeO3, and LaNiO3. The pH-dependent OER activities, H/D kinetic isotope effect, and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate-limiting steps of the OER. For oxides with small charge-transfer energies, such as LSCO and LaNiO3, non-concerted proton-coupled electron transfer steps are involved in the OER, and the activity is strongly controlled by the proton dynamics on the catalyst surface. The results demonstrate the important role of interfacial proton transfer in the OER mechanism, and suggest that proton dynamics at the interface should carefully be considered in the design of future high-performance catalysts.