Low-Cost Ni₂P/Ni_0.96S Heterostructured Bifunctional Electrocatalyst toward Highly Efficient Overall Urea-Water Electrolysis

Water splitting is a sustainable approach for production of hydrogen to fuel some clean energy technologies. This process, unfortunately, has been significantly impeded by the puzzles in either the efficient but economically unaffordable noble-metal-based catalysts or the low-cost but kinetically sluggish abundant-element-based catalysts. Particularly, the discovery of efficient bifunctional catalysts that can simultaneously trigger the reactions of both anode and cathode for overall water splitting still remains as a grand challenge. Herein, a novel low-cost bifunctional Ni₂P/Ni_0.96S heterostructured electrocatalyst, which is active for both the urea oxidation reaction at the anode and the hydrogen evolution reaction at the cathode, is innovated for high-efficiency overall splitting of urea-rich wastewater. A systematic configuration of a Ni foam (NF)-supported Ni₂P/Ni_0.96S catalyst electrode exhibits superior catalytic activity and stability. The Ni₂P/Ni_0.96S/NF||Ni₂P/Ni_0.96S/NF cell needs only 1.453 V to reach a current density of 100 mA/cm² in basic urea-containing water, while it is 1.693 V for a reference noble-based Pt/C/NF||IrO₂/NF electrolysis cell. This work therefore not only contributes to develop a low-cost, high-efficiency, bifunctional electrocatalyst but also provides a practically feasible approach for urea-rich wastewater treatment.