Lattice Strain and Built-In Field Synergistically Boost Urea Oxidation via Dynamic NiOOH Mediation at Multiphase Heterointerfaces.

Abstract

The practical application of nickel-based heterojunction electrocatalysts for the urea oxidation reaction (UOR) is impeded by insufficient active sites and sluggish multi-step reaction kinetics. Herein, a sulfur-doped lignin-derived carbon encapsulated Ni-NiO-MoO₂ micro-nano array (Ni-NiO-MoO₂@SC) is fabricated to tackle these issues. Experimental and theoretical results demonstrate that the multiphase heterointerfaces spontaneously generate a built-in electric field due to the distinct work function and electronic structure of each component, and simultaneously induce lattice strain, which synergistically optimizes the electronic structure and accelerates the dynamic formation of active NiOOH species. In-situ electrochemical characterizations and density functional theory calculations further confirm that the engineered interface promotes urea adsorption, facilitates N─N coupling and C─N bond cleavage, expedites *COOH intermediate desorption, and avoids excessive accumulation of NiOOH. Consequently, Ni-NiO-MoO₂@SC delivers superior UOR activity with low potentials of 1.34/1.40 V at 10/500 mA cm^-2, respectively. Moreover, the sulfur-doped carbon encapsulation and micro-nano array architecture endow the catalyst with excellent corrosion resistance and mass transport capability, realizing long-term stability (500 mA cm^-2 at 1.53 V for 500 h) in membrane electrode assemblies. This work provides a versatile interface engineering and encapsulation strategy for high-performance nickel-based electrocatalysts toward urea electrolysis and beyond.