Nanostructured Fe-ZIF Supported on Ni Foam as Electrocatalyst for the Oxygen Evolution Reaction

Developing and constructing highly stable and active electrocatalysts for the water oxidation or oxygen evolution reaction (OER) remains critical for achieving efficient water splitting. Herein, we report the in situ transformation of iron–cobalt hydroxycarbonate directly grown on nickel foam (NF) into nanostructured Fe 0.2 ZIF(67 + 9)/NF via a ligand-engineering strategy using a solvothermal approach. Post-OER characterization reveals a slight increase in oxygen content, suggesting surface reconstruction during electrochemical operation. The obtained Fe 0.2 ZIF(67 + 9)/NF exhibits outstanding catalytic performance, revealed in a low overpotential value of only 250 mV to reach the current density of 50 mA cm –2 with a small Tafel slope of 60 mV dec –1, indicative of accelerated reaction kinetics and favorable charge-transfer characteristics. Moreover, the electrochemically active surface area (ECSA) taken before and after 100 C–V cycles shows a 6.5% increase, indicating a structural activation, which is supported by an enhancement of anodic charge by about 13% as compared to Fe 0.2 ZIF-9/NF. Furthermore, just a 2 mV increase in potential after a 24 h chronopotentiometry test and a 37 mV decrease to sustain 25 mA cm –2 current density depicted the high stability and surface activation in Fe 0.2 ZIF(67 + 9)/NF. The enhanced catalytic efficiency is further supported by activation energy calculations, confirming improved reaction energetics. Moreover, from the Tafel slope analysis, the K H / K D ratio was calculated, which comes to about 0.42, suggesting a strong inverse kinetic isotopic effect, indicating that proton transfer is not involved in the rate-determining step and that O–H bond cleavage does not control the reaction kinetics. Overall, this study highlights ligand engineering as an effective strategy to regulate structural transformation and surface reconstruction, offering a promising pathway for the rational design of advanced nanostructured ZIF-based electrocatalysts for efficient and durable water oxidation.