Built‐In Electric Field in MoS ₂ /NiMoO ₄ Heterojunction Modulates Ni ²⁺ /Ni ³⁺ Cycling to Optimize the Urea Oxidation Reaction Pathway

ABSTRACT The electrocatalytic urea oxidation reaction (UOR) demonstrates significant potential in energy conversion and wastewater treatment. In nickel‐based electrocatalytic systems, the UOR process characterized by NiOOH (Ni ³⁺ ) formation in the conventional pathway tends to generate harmful by‐products at high potentials while facing oxygen evolution reactuion (OER) competition. Herein, we synthesized a MoS ₂ /NiMoO ₄ heterostructure and regulate the built‐in electric field in the heterojunction, while the conversion process from Ni ³⁺ to Ni ²⁺ is accelerated, thus resulting in a reduction in the static accumulation of Ni ³⁺ . This delays the cleavage of the carbon‐nitrogen (C─N) bond, thereby steering the reaction pathway toward the complete oxidation products, CO ₂ and N ₂ . The MoS ₂ /NiMoO ₄ catalyst exhibits exceptional electrocatalytic activity toward UOR, requiring a low driving potential of just 1.365 V to achieve a current density of 100 mA cm ⁻² . The urea electrolyzer assembled with MoS ₂ /NiMoO ₄ and Pt electrodes achieves the same current density at 1.61 V and operates stably for 180 h. This work provides fundamental insights into the UOR mechanism and offers a new direction for designing efficient nickel‐based heterostructure catalysts.