A facile surface engineering approach for fabricating the superwetting Ni–Fe–Co LDH@Ni–S heterojunction as a bi-functional electrode for green hydrogen production: experiment and theory

Abstract

In comparison to the oxygen evolution reaction (OER), the urea electrooxidation reaction (UOR) is a more energy-efficient technique for producing hydrogen. To make this process economically viable, stable and effective electrocatalysts are essential. In two steps, this study created a Ni–Fe–Co LDH/Ni–S/NF electrocatalyst: using the dynamic hydrogen bubble template (DHBT) method, a porous Ni–S structure was first electrodeposited on nickel foam (NF). Next, Ni–Fe–Co nanosheets were created via cyclic voltammetry (CV). The electrocatalyst showed excellent activity for both the hydrogen evolution reaction (HER) and UOR, with HER performances of −73 and −173 mV vs. RHE, and UOR performances of 1.32 and 1.37 V vs. RHE at 10 and 100 mA cm⁻², respectively. These UOR values were significantly lower than the OER values. In a two-electrode system, the electrocatalyst exhibited cell voltages of 1.42 V at 10 mA cm⁻² and 1.71 V at 100 mA cm⁻². The preparation process enhanced the electrochemically active surface area (ECSA), exposing more active sites. The catalyst showed remarkable durability in a 50-hour stability test at 100 mA cm⁻², with excellent mass transportability attributed to its porous structure. DFT calculations further validated the electronic coupling between Ni–Fe–Co LDH and Ni–S, highlighting the role of charge redistribution in optimizing catalytic activity. This work provides a cost-effective and scalable strategy for designing efficient bifunctional electrocatalysts for sustainable hydrogen production and urea-rich wastewater treatment.