Rapid Two Surface Reconstructions of Ni/MnO Heterojunction for Superior Urea Electrolysis

Urea oxidation reaction (UOR) emerges as a promising alternative anodic half-reaction to oxygen evolution reaction (OER) in an electrochemical CO2 reduction reaction (ECRR) system. Herein, a Ni/MnO heterojunction with extraordinary UOR activity is synthesized on Ni foam. Ex situ/in situ characterization and theoretical calculation reveal that the outstanding UOR performance of Ni/MnO catalyst can be ascribed to two successive surface reconstructions. In the first and second surface reconstructions, Ni­(OH)2/MnOOH and NiOOH/MnOOH heterojunctions are formed on the catalyst surface, and Mn and Ni sites serve as the active sites, respectively. The heterojunctions formed can enhance UOR activity by reducing the surface reconstruction potential and optimizing the adsorption energy of intermediates through electronic structure modulation and d-band center regulation. When employed as the UOR anode in the CO2 electrolyzer, it requires 375 mV less voltage at 10 mA cm–2 than the OER, revealing the great potential of applying such Ni/MnO catalyst as the anodic UOR in an ECRR system for carbon neutrality.