Surface Reconstruction of an FeNi Foam Substrate for Efficient Oxygen Evolution

Designing earth-abundant electrocatalysts that are highly active, low-cost, and stable for the oxygen evolution reaction (OER) is crucial for electrochemical water splitting. However, in conventional electrode fabrication strategies, NiFe layered double hydroxide (NiFe LDH) catalysts are usually coated onto substrates as external components, which suffers from poor conductivity, easily detaches from the substrate, and hinders their long-term utilization. Herein, the surface-reconstruction strategy is used to synthesize in situ autologous NiFe LDH to increase the surficial active sites numbers. The FeNi foam (FNF) serves as both the metal source and substrate, and the obtained NiFe LDH nanosheets (NSs) are firmly anchored in the monolithic FNF. What needs to be emphasized is that the strategy does not involve any high-temperature or high-pressure processes, apart from a cost-effective etching and a specified drying treatment. The nanostructure of NiFe LDH and the synergistic effect between Fe and Ni simultaneously lead to an enhanced catalytic effect for the OER. Remarkably, the sr-FNF46 requires only an ultralow overpotential of 283 mV to achieve a current density of 100 mA cm-2 for the OER in 1 M KOH electrolyte, and exhibits excellent stability. Thus, the obtained electrode holds promise for electrocatalytic applications. Finally, the formation mechanism of NiFe LDH NSs due to surface reconstruction is investigated and discussed in detail.