Enhancing Localized Electron Density over Pd1.4Cu Decorated Oxygen Defective TiO2‐x Nanoarray for Electrocatalytic Nitrite Reduction to Ammonia

Electrocatalytic nitrite (NO2−) reduction to ammonia (NH3) is a promising method for reducing pollution and aiding industrial production. However, progress is limited by the lack of efficient selective catalysts and ambiguous catalytic mechanisms. This study explores the loading of PdCu alloy onto oxygen defective TiO2‐x, resulting in a significant increase in NH3 yield (from 70.6 to 366.4 µmol cm−2 h−1 at −0.6 V vs reversible hydrogen electrode) by modulating localized electron density. In situ and operando studies illustrate that the reduction of NO2− to NH3 involves gradual deoxygenation and hydrogenation. The process also demonstrated excellent selectivity and stability, with long‐term durability in cycling and 50 h stability tests. Density functional theory (DFT) calculations elucidate that the introduction of PdCu alloys further amplified electron density at oxygen vacancies (Ovs). Additionally, the Ti─O bond is strengthened as the d‐band center of the Ti 3d rising after PdCu loading, facilitating the adsorption and activation of *NO2. Moreover, the presence of Ovs and PdCu alloy lowers the energy barriers for deoxygenation and hydrogenation, leading to high yield and selectivity of NH3. This insight of controlling localized electron density offers valuable insights for advancing sustainable NH3 synthesis methods. This study elucidates the mechanism of modulating and amplifying localized electron density in OvTPd1.4Cu electrocatalysts for ammonia (NH3) production, resulting in improved catalytic efficiency. In situ and operando investigations demonstrate that the introduction of oxygen vacancies (Ovs) and PdCu lowers energy barriers of deoxygenation and hydrogenation, thereby facilitating the adsorption and activation of *NO2. These findings offer valuable insights for advancing sustainable NH3 synthesis.