Ni(OH)2/CeO2 heterointerface catalysts for energy-efficient urea electrooxidation

초록

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 alpha-Ni(OH)2 to beta-Ni(OH)2, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal the 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 Ni(OH)2/MnO2, the Ni(OH)2/CeO2 composite exhibits a lower UOR potential of 0.534 V vs. Ag/AgCl to reach 10 mA cm-2, and 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 mu F 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.

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