Effective regulation mechanisms of Fe-Ni(oxy)hydroxide: Ni-rich heteroatomic bonding (Ni–O–Fe–O–Ni) is essential

Although Fe-Ni combination performs well in transition metal-based oxygen evolution reaction (OER) electrocatalysts, there are lack of clear and general regulations mechanism to fully play the synergistic catalytic effect. Here, we made the utmost of the interaction of Fe–Ni heteroatomic pair to obtain a highly active Fe-Ni(oxy)hydroxide catalytic layer on iron foam (IF) and nickel foam (NF) by in-situ electrochemical deposition and rapid surface reconstruction, which only required 327 and 351 mV overpotential to provide a large current of 1,000 mA·cm⁻², respectively. The results confirm that the moderate Ni-rich heteroatomic bonding (Ni–O–Fe–O–Ni) formed by adjusting the Ni/Fe ratio on the catalyst surface is important to offer predominant OER performance. Fe is a key component that enhances OER activity of Ni(O)OH, but Fe-rich structural surface formed by Fe–O–Ni–O–Fe bonding is not ideal. Finally, the remarkable oxygen evolution performance of the prepared Ni₂Fe(O)OH/IF and FeNi₂(O)OH/NF can be chalked up to the optimized electronic structure of Fe–Ni heteroatomic bonding, the efficient gas spillover, the fast electron transport, and nanosheet clusters morphology. In summary, our work suggests a comprehensive regulation mechanism for the construction of efficient Fe-Ni(oxy)hydroxide catalytic layer on inexpensive, stable, and self-supporting metallic material surface.