MoP@NiCo-LDH on nickel foam as bifunctional electrocatalyst for high efficiency water and urea–water electrolysis

Abstract

Water electrolysis is an important way to produce hydrogen at the cathode, but the oxygen evolution reaction (OER) at the anode has a high overpotential. Using the urea oxidation reaction (UOR) to replace OER has been an energy-saving approach for its lower electrode potential, and also a potential approach for wastewater treatment. In this paper, novel materials of MoP@NiCo-LDH/NF-x (x = 10, 20, 30 minutes) are synthesized and explored as bifunctional catalysts for both the hydrogen evolution reaction (HER) at the cathode and the urea oxidation reaction (UOR) or the oxygen evolution reaction (OER) at the anodes of urea–water or water electrolysis. The morphologies and compositions of such catalyst materials are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The catalytic activity and stability are measured by linear sweep voltammetry, electrochemical impedance spectroscopy, chronoamperometry, etc. The results indicate that MoP@NiCo-LDH/NF-20 has better catalytic performance, and can be used as a bifunctional catalyst for both HER and OER/UOR in the electrolysis. A two-electrode electrolyser (MoP@NiCo-LDH/NF-20‖MoP@NiCo-LDH/NF-20) is constructed. At 100 mA cm⁻², the two-electrode electrolyser needs only 1.405 V, while the precious metal electrolyser Pt/C/NF‖IrO₂/NF needs 1.697 V at the same current density, indicating that MoP@NiCo-LDH/NF-20 could be a promising bifunctional electrocatalyst in water and urea–water electrolysis for the treatment of urea wastewater and hydrogen production.