High-valent metal site incorporated heterointerface catalysts for high-performance anion-exchange membrane water electrolysers

The design of heterointerface-structured catalysts with tunable active sites is critical to address the activity and durability challenges of water oxidation process. In this study, a novel interfacial engineering strategy based on the anionic diffusion-limited Kirkendall effect (KE) was employed for the synthesis of a FeCo/FeCoP with high-valent Fe (Fe+3.18) sites. Specifically, a model system of the FeCo/FeCoP heterointerface was obtained through the phosphidation of carbon-encapsulated FeCo nanoparticles. The highly efficient and stable oxygen evolution reaction (OER) performance of the FeCo/FeCoP catalyst was demonstrated in an anion-exchange membrane water electrolyser (12.26 A cm–2 at 2.0 V). Through density functional theory calculations, the high-valent Fe sites in the FeCo/FeCoP heterointerface were found to balance the adsorption energetics of the OER intermediates. The structure–oxidation state–OER activity correlation of the FeCo/FeCoP catalysts demonstrated herein emphasises the significance of understanding the water oxidation chemistry of heterointerface-structured catalysts for their potential applications in different energy conversion devices.