Improved Urea Oxidation Performance via Interface Electron Redistributions of the NiFe(OH) x /MnO 2 /NF p-p Heterojunction.

The development of highly efficient urea oxidation reaction (UOR) electrocatalysts is the key to simultaneously achieving green hydrogen production and the treatment of urea-containing wastewater. Ni-based electrocatalysts are expected to replace precious metal catalysts for UOR because of their high activity and low cost. However, the construction of Ni-based electrocatalysts that can synergistically enhance UOR still needs further in-depth study. In this study, highly active electrocatalysts of NiFe(OH) x /MnO 2 p-p heterostructures are constructed on nickel foam (NF) by electrodeposition (NiFe(OH) x /MnO 2 /NF), illustrating the effect of electronic structure changes at heterogeneous interfaces on UOR and revealing the catalytic mechanism of UOR. The NiFe(OH) x /MnO 2 /NF only needs 1.364 V (vs Reversible Hydrogen Electrode, RHE) to reach 10 mA cm -2 for UOR. Structural characterizations and theoretical calculations indicate that energy gap leads to directed charge transfer and redistribution at the heterojunction interface, forming electron-rich (MnO 2 ) and electron-poor (NiFe(OH) x ) regions. This enhances the catalyst's adsorption of urea and reaction intermediates, reduces thermodynamic barriers during the UOR process, promotes the formation of Ni 3+ phases at lower potentials, and thus improves UOR performance. This work provides a new idea for the development of Ni-based high-efficiency UOR electrocatalysts.