Electrochemical Enhancement of Copper in a Nickel–Iron Layered Double Hydroxide Catalyst for Alkaline Oxygen Evolution Reactions

The development of an efficient and cost-effective oxygen evolution reaction (OER) catalyst is important in increasing the overall efficiency of the electrochemical water splitting process to produce green hydrogen. In this work, the substitution of copper in NiFe layered double hydroxide (LDH) was utilized to improve the sluggish kinetics of the water oxidation process. The simple in situ hydrothermal method was used to introduce copper into the NiFe LDH structure. All of the prepared catalysts displayed a sheet-like morphology, with the optimized NiCuFe LDH sample exhibiting a BET specific surface area of 117.5 m² g^-1. The optimized Cu-substituted LDH exhibited a superior performance in the alkaline water splitting process by requiring a lower overpotential of 230 mV to attain a current density of 10 mA cm^-2, accompanied by a low Tafel constant of 47.7 mV dec^-1, by outperforming the pristine NiFe LDH. The electronic structure modification of NiFe LDH by Cu atoms favors the OER process, which is verified by the density functional theory (DFT). Further, the optimized electrode was utilized in real-world conditions of the saline-alkaline electrolyte for water splitting, necessitating a minimal overpotential of 247.5 mV to oxidize water, and the electrode demonstrated long-term stability. Thus, NiCuFe LDH is a potential OER catalyst for large-scale electrochemical water splitting applications.