Grain Boundary-Mediated Electrocatalytic C−N Coupling for Urea Synthesis from CO2 and NOx

Abstract

Electrocatalytic urea synthesis from CO2 and NOx offers a sustainable route for chemical production and environmental remediation. While grain-boundary engineering has emerged as a promising strategy to accelerate the sluggish kinetics of C–N coupling, whether it can simultaneously regulate the reaction pathways of both carbon and nitrogencontaining molecules remains unclear. Hence, we employed single-active-site TiO2 as a model catalyst and constructed polycrystalline grain boundaries to boost both the activity and selectivity of urea synthesis. Atomic-scale structural inducers (Fe) served as nucleation nodes for grain-boundary formation and promote the generation of abundant oxygen vacancies, which captured and locally concentrated electrons to facilitate the adsorption, activation, and C−N coupling of key reaction intermediates. Operando electrochemical impedance spectroscopy demonstrated enhanced interfacial charge transfer and faster interfacial response frequencies. In situ infrared spectroscopy directly tracked the adsorption and activation of both reactants as well as the formation of the critical C–N bond. This work provides a general design principle for developing advanced electrocatalysts for efficient C–N coupling.