Synergistic Coupling of CuNi Alloy with CoFe LDH Heterostructure on Nickel Foam toward High-Efficiency Overall Water Splitting

Accelerating the kinetics of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital for high-efficiency green hydrogen production. However, developing cost-effective and highly active bifunctional catalysts for overall water splitting electrolysis remains a huge challenge. Herein, CuNi/CoFe LDH heterostructure is synthesized in situ on the nickel foam (CuNi/CoFe LDH@NF) by a simple two-step electrodeposition process. The synergy of CuNi alloy and CoFe LDH optimizes the electron distribution at the interface and improves the intrinsic activity of HER/OER. Consequently, the optimal CuNi/CoFe LDH@NF bifunctional catalyst displays low overpotentials of 56 mV (10 mA cm−2) and 268 mV (50 mA cm−2) for HER and OER, respectively, along with high stability in alkaline electrolyte. Remarkably, CuNi/CoFe LDH@NF as the cathode and anode requires a low voltage (1.49 V) to achieve 10 mA cm−2 for overall water splitting. Meanwhile, it also displays favorable stability for operation for 17 h (50 mA cm−2) without obvious decline of cell voltage. Density functional theory calculations indicate that constructing heterojunction interfaces promotes the redistribution of interface electrons and optimizes the free energy of adsorbed intermediates, thereby reducing the energy barrier of the rate-determining step (from *O to *OOH).