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

Abstract 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.