Carbon-Bifunctionalized Mo2N Coupled Atomic Pb Sites for Efficient Nitrogen Reduction.

The electrocatalytic nitrogen reduction reaction (ENRR) offers a sustainable pathway for ambient ammonia (NH3) synthesis but suffers from kinetic limitations and competing hydrogen evolution (HER). Herein, a new type of ENRR catalyst is designed consisting of carbon-bifunctionalized Mo2N nanoparticles (NPs) embedded in a hierarchical porous carbon matrix with atomic Pb sites (PbNC) through a one-step carbonitridation strategy. The carbon-bifunctionalization effect not only creates nitrogen vacancies through interstitial carbon doping to form molybdenum carbonitride (Mo2CN) phase that enhances N2 adsorption and activation, but also stabilizes active sites via nanoconfinement of the in situ formed carbon layer on Mo2CN NPs. Concurrently, the atomically dispersed Pb within the PbNC matrix suppresses HER due to its weak H* affinity. The optimized catalyst demonstrates 38.7 µg h-1 mg-1 NH3 yield at a low potential of -0.1 V with 50 h operational stability. Density functional theory calculations reveal that carbon-induced nitrogen vacancies modulate the Mo d-band center, which facilitates electron back-donation to N2 and thus shifts the potential-determining step from initial protonation to the NH3 desorption step via the Mars-van Krevelen mechanism with a lower energy barrier for ENRR. This study proposes an integrated approach involving vacancy engineering, atomic-level HER suppression, and nanoconfinement toward efficient ENRR catalysis.