Ni₃N/NF as Bifunctional Catalysts for Both Hydrogen Generation and Urea Decomposition

Abstract

Oxygen evolution reaction (OER) has a high overpotential, which can significantly reduce the energy efficiency in water decomposition. Using urea oxidation reaction (UOR) to replace OER has been a feasible and energy-saving approach because of its lower electrode potential. Furthermore, UOR is also an important process in wastewater treatment. This paper successfully synthesizes a high-performance bifunctional catalyst for urea electrolysis. The catalyst is nickel nitride bead-like nanospheres array supported on Ni foam (Ni₃N/NF). Several characterization methods are used to analyze the catalyst's morphology, structure, and composition as well as catalytic activity/stability, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical methods (cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, and CAM). A concurrent two-electrode electrolyzer (Ni₃N/NF∥Ni₃N/NF) is constructed and used to validate the catalyst performance, and the results show that the cell achieves 100 mA·cm^-2 at 1.42 V, while the cell voltage of Pt/C∥IrO₂ is 1.60 V, indicating that the Ni₃N/NF catalyst is superior to precious metals.