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/TiO_2-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/TiO_2-x catalyst attains a high rate of NH₃ evolution, reaching 5.0 mmol g_cat. ^-1 h^-1. This work paves a pathway of defect-engineering metal-supported electrocatalysts for high-efficient ammonia electrosynthesis.