Synthesis bifunctional catalysts with amorphous NiFe-LDH/crystalline CoMo bimetallic phosphide heterojunction by electrodeposition for efficient water splitting

Designing and preparing an efficient bifunctional catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for achieving electrochemical water splitting. Constructing amorphous/crystalline heterojunctions catalysts are considered an effective method to enhance bifunctional catalytic activity, In this work, we developed an interfacial engineering strategy to prepare a three-dimensional amorphous NiFe layered double hydroxide/crystalline CoMo bimetallic phosphide heterojunction bifunctional composite material NiFe-LDH@CoMo–P on nickel foam using a simple and efficient electrodeposition method. Combining the crystalline CoMo–P for enhanced HER catalytic activity with the amorphous NiFe-LDH for superior OER catalytic activity ensures the bifunctional catalytic performance. Moreover, the formation of unique amorphous/crystalline heterointerfaces accelerates electron transfer, inducing electron rearrangement at the interface and resulting in more suitable Gibbs adsorption energies for catalytic reaction intermediates. This significantly enhances the catalytic reaction kinetics and improves the electrocatalytic activity. Density functional theory (DFT) calculations and experimental studies have shown that the d-band center of the active sites in NiFe-LDH@CoMo–P catalyst shifts towards the Fermi level, thereby optimizing the adsorption strength of catalytic reaction intermediates on the catalyst surface. In 1 M KOH, as a bifunctional catalyst, NiFe-LDH@CoMo–P/NF requires an anodic overpotential of 236 mV to achieve an OER current density of 20 mA cm⁻², and a cathodic overpotential of −49 mV to achieve a HER current density of −10 mA cm⁻². The study provides a new approach for the efficient and low-cost preparation of amorphous/crystalline heterojunction bifunctional catalysts.