Abstract: Renewable energy-driven water electrolysis is considered as an environmentally friendly hydrogen (H₂) production technology. Replacing the oxygen evolution reaction (OER) with the urea oxidation reaction (UOR) is a more effective way to improve the energy efficiency of H₂ generation. Herein, a highly efficient 2D NiFeMo-based UOR catalyst and 1D NiFeMo-based HER catalyst are prepared by adjusting the concentration of MoO₄^‒. The MoO₄^‒ can serve as the key regulator to adjust the balance between the electrolytic dissociation (α) of the reactants and the supersaturation (S) to modulate the morphological and electronic structure. The prepared 2D NiFeMo nanosheet UOR catalyst and 1D NiFeMo nanorod HER catalyst can achieve a current density of 100 mA cm^-2 at a potential of 1.36 and 0.062 V, respectively. In a HER/UOR system, a cell voltage of 1.58 V is needed to achieve a current density of 100 mA cm^-2. The HER/UOR system operated stably for over 60 h with 3 times the direct water electrolysis current density. Moreover, the in situ Raman characterization coupled with XPS analysis clarifies that the addition of high-valence Mo can lower the transition energy barrier between the low and high oxidation state of Ni, which in turn lowers the overpotential of UOR. This work provides a novel strategy for synthesizing morphology-dependent electrocatalysts for different catalytic systems.

Key words: Urea oxidation reaction, NiFe-based catalyst, Hydrogen evolution, Morphological and electronic structure, Active sites