Ni(OH)₂/CeO₂ Heterointerface catalysts for Energy Efficient Urea Electrooxidation

Abstract

The electrochemical urea oxidation reaction (UOR) is an important half-reaction involved in urea electrolyzers and direct urea fuel cells. However, its practical implementation is hindered by sluggish kinetics and catalyst passivation. Herein, we report a facile hydrothermal synthesis of a Ni(OH)₂/CeO₂ hybrid electrocatalyst (molar ratio 2:1) that addresses these challenges through a well engineered heterointerface. X ray diffraction (XRD) confirms the phase transition from α Ni(OH)₂ to β Ni(OH)₂, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal uniform Ni(OH)2/CeO₂ dispersion and nanoscale morphology. X ray photoelectron spectroscopy (XPS) identifies abundant oxygen vacancies and strong electronic coupling between Ni and Ce species. Compared to pristine Ni(OH)₂, CeO₂, and a Ni(OH)₂/MnO₂, the Ni(OH)₂/CeO₂ composite exhibits lower UOR potential of 0.534 V vs. Ag/AgCl to reach 10 mA cm⁻², a Tafel slope of 105 mV dec⁻¹ signifying its improved electrocatalytic activity. Electrochemical double layer capacitance measurements reveal a threefold increase in Cdl (610 µF cm⁻²) relative to Ni(OH)₂/MnO₂, indicating a dramatically enlarged electrochemically active surface area. The combination of rapid charge transfer and favorable surface characteristics positions Ni(OH)₂/CeO₂ as a promising catalyst for electrooxidation of urea.