In situ iron coating on nanocatalysts for efficient and durable oxygen evolution reaction

The oxygen evolution reaction (OER) is essential to many important energy conversion and storage systems. To achieve high-performance and low-cost OER electrocatalysts, great effort has been devoted to the development of noble-metal-free OER nanocatalysts. While nanostructured materials have been shown effective at improving the catalytic activity, the stability of the nanocatalyst has yet to be significantly improved. Furthermore, nanocatalyst syntheses are typically complex, limiting their practical application. Herein, we design a noble-metal-free nanocatalyst which has a CoFePx core and an in situ Fe coating layer to enhance the material's catalytic activity and durability for OER. We utilize the vapor pressure difference of Fe and Co at high temperature to synthesize the CoFePx-Fe core-shell nanoparticles via a one-step high-temperature shock technique. The high-temperature method strongly anchors the CoFePx nanoparticles onto a carbon substrate. The thin Fe shell layer (~2 nm) coated on the CoFePx greatly enhances the durability of the CoFePx catalyst without hampering its activity due to the geometric effect. This nanocatalyst with an in situ Fe shell demonstrates a successful nanocoating approach for fabricating catalytically active protection layers on catalysts with improved activity and durability.