Controllable Phase Separation Engineering of Iron-Cobalt Alloy Heterojunction for Efficient Water Oxidation

The tailor-made transition metal alloy-based heterojunctions hold a promising prospect for the electrocatalytic oxygen evolution reaction (OER). Herein, a series of iron-cobalt bimetallic alloy heterojunctions are purposely designed and constructed via a newly developed controllable phase separation engineering strategy. The results show that the phase separation process and alloy component distribution rely on the metal molar ratio (Fe/Co), indicative of the metal content dependent behavior. Theoretical calculations demonstrate that the electronic structure and charge distribution of iron-cobalt bimetallic alloy can be modulated and optimized, thus leading to the formation of an electron-rich interface layer, which likely tunes the d-band center and reduces the adsorption energy barrier toward electrocatalytic intermediates. As a result, the Fe_0.25Co_0.75/Co heterojunction exhibits superior OER activity with a low overpotential of 185 mV at 10 mA cm^-2. Moreover, it can reach industrial-level current densities and excellent durability in high-temperature and high-concentration electrolyte (30 wt % KOH), exhibiting enormous potential for industrial applications.