Boosting the Electrocatalytic Urea Oxidation Performance by Amorphous–Crystalline Ni-TPA@NiSe Heterostructures and Mechanism Discovery

Developing cost-effective electrocatalysts and elucidating the in situ catalytic mechanism of the urea oxidation reaction (UOR) is a cornerstone for developing urea-based technology. Amorphous–crystalline (A–C) heterostructures have attracted extensive attention owing to their highly exposed active sites and superior stability. However, the complicated synthesis approach and inefficient A–C boundary severely limit their industrial application in UOR electrolysis. In this study, a simple hydrothermal method was reported to fabricate novel heterostructure nanoarrays comprising NiSe nanorods evenly integrated with nickel-terephthalic acid (Ni-TPA) nanosheets. In the A–C heterostructure electrocatalyst, highly conductive NiSe nanorods facilitate axial charge transfer in the interconnection network. TPA-induced formation of crystalline–amorphous heterostructures exposes more active sites and regulates the electronic structure of Ni. As expected, the optimal Ni-TPA@NiSe/NF electrode presents a low potential of 1.37 V to deliver 100 mA cm–2 for UOR while maintaining impressively robust stability at high current densities for at least 40 h. In situ electrochemical Raman spectroscopy and differential electrochemical mass spectrometry analyses reveal that the superior UOR activity originates from NiOOH species and the terminal product of nitrogen is generated via intramolecular N–N coupling in the urea molecule. More importantly, this study offers deep insights into designing and fabricating effective UOR electrocatalysts with abundant A–C grain boundaries.