A crystalline/amorphous FeCo alloy/FeCoNi-Pi bifunctional electrocatalyst for efficient overall water splitting

Electrochemical water splitting is crucial for sustainable energy and environmental conservation, meeting global energy needs while addressing environmental concerns. However, unlocking its potential requires addressing substantial technical and scientific challenges. Crystalline/amorphous composite catalysts represent a significant advancement in water-splitting research, with unique structural compositions and tailored properties that outperform conventional catalysts, thereby enhancing the efficiency and performance in essential aspects. In this study, crystalline/amorphous-structured FeCo alloy/FeCoNi-Pi (phosphate) was synthesized through one-step electrodeposition on Ni foam (NF). While FeCo alloy demonstrates excellent conductivity, the incorporation of FeCoNi-Pi enhances active site availability, improves hydrophilicity, and optimizes electrocatalytic reaction kinetics. Consequently, crystalline/amorphous FeCo alloy/FeCoNi-Pi required significantly lower overpotentials of 77/233 mV for the hydrogen/oxygen evolution reaction (HER/OER) compared to the FeCo alloy to acquire 10 mA cm⁻² current density in an alkaline environment. A complete cell comprised of crystalline/amorphous FeCo alloy/FeCoNi-Pi electrodes exhibits remarkable long-term stability and demonstrates a relatively lower voltage of 1.56 and 1.69 V, enabling 10 and 100 mA cm⁻² current densities. This crystalline/amorphous composite strategy has been proven effective in designing FeCo alloy-based electrocatalysts to achieve efficient hydrogen production.