Ligand-Engineered p-Orbital Occupancy Modulation Activates Lattice Oxygen for Efficient and Selective Urea Electrooxidation

Electrochemical urea oxidation reaction (UOR) offers a promising alternative to oxygen evolution reaction (OER) in water electrolysis, enabling simultaneous energy-efficient hydrogen production and urea-rich wastewater remediation. However, sluggish kinetics and the inevitable competition from OER, especially at high anodic potentials, continue to impede its practical application. Herein, we report a ligand-engineered NiFe layered double hydroxide intercalated with trifluoroacetate (CF₃COO^–), termed CF₃-LDH, to address these limitations. Leveraging the strong electron-withdrawing nature of the –CF₃ group, CF₃COO^– drives electron transfer from Ni and Fe centers to the ligand, thereby lowering the local electron density, stabilizing high-valent Ni^(2+δ)+ and Fe^(3+α)+ species, and unlocking the reactivity of adjacent lattice oxygen sites. In situ spectroscopic analyses reveal that CF₃COO^– intercalation suppresses NiOOH formation and mitigates OH^– oversaturation, thus attenuating the parasitic OER pathway and ensuring UOR selectivity. Theoretical calculations further confirm that the lattice oxygen sites with engineered p-orbital occupancy reduce the energy barriers of key UOR steps and optimize the adsorption of critical intermediates. As a result, CF₃-LDH exhibits superior UOR activity, requiring only 1.32 V to reach 10 mA cm⁻² with a Tafel slope of 29 mV dec⁻¹. When integrated into an anion exchange membrane (AEM) electrolyzer, the system delivers 100 mA cm⁻² at just 1.36 V at 60°C and maintains stable operation over 200 h. This work highlights the efficacy of ligand-directed lattice oxygen activation in promoting pathway-selective UOR and presents a viable strategy for designing high-performance anodes toward integrated clean hydrogen generation and wastewater treatment.