Vacancy-Mediated Control of Local Electronic Structure for High-Efficiency Electrocatalytic Conversion of N2 to NH3.

Ambient electrocatalytic nitrogen (N2) reduction has gained significant recognition as a potential substitute for producing ammonia (NH3). However, N2 adsorption and *NN protonation for N2 activation reaction with the competing hydrogen evolution reaction remain a daunting challenge. Herein, a defect-rich TiO2 nanosheet electrocatalyst with PdCu alloy nanoparticles (PdCu/TiO2-x) is designed to elucidate the reactivity and selectivity trends of N2 cleavage path for N2-to-NH3 catalytic conversion. The introduction of oxygen vacancy (OV) not only acts as active sites but also effectively promotes the electron transfer from Pd-Cu sites to high-concentration Ti3+ sites, and thus lends to the N2 activation via electron donation of PdCu. OVs-mediated control effectively lowers the reaction barrier of *N2H and *H adsorption and facilitates the first hydrogenation process of N2 activation. Consequently, PdCu/TiO2-x catalyst attains a high rate of NH3 evolution, reaching 5.0 mmol gcat. -1 h-1. This work paves a pathway of defect-engineering metal-supported electrocatalysts for high-efficient ammonia electrosynthesis.