Synergistic W-doping and Co3S4 heterostructuring in NiFe LDH for energy-saving hydrogen production via urea-assisted water electrolysis

Abstract

The development of efficient electrocatalysts to replace the sluggish oxygen evolution reaction (OER) with the urea oxidation reaction (UOR) is crucial for achieving energy-saving hydrogen production. To this end, we constructed a heterostructure comprising W-doped NiFe layered double hydroxide (W-NiFe LDH) and Co₃S₄ on a nickel foam (NF) substrate using a two-step hydrothermal method. The incorporation of W dopants and the formation of a heterointerface induce significant electron redistribution, leading to an optimized electronic structure. The resulting W-NiFe LDH@Co₃S₄/NF electrode exhibited exceptional electrocatalytic activity for the UOR, which required only 1.41 V to achieve a current density of 100 mA cm⁻² in 1 M KOH with 0.33 M urea. This potential is 119 mV lower than that required for the OER at the same current density, highlighting the significant energy-saving advantage of the urea oxidation pathway. When integrated into an anion exchange membrane electrolyzer, the electrode enables overall urea-assisted water splitting at a low cell voltage of 1.83 V (100 mA cm⁻²). Density functional theory calculations indicate that the remarkable UOR performance stems from enhanced adsorption of the CO(NH₂)₂* intermediate and a reduced energy barrier for the dehydrogenation step to CO* and NH*.