Enhancing Localized Electron Density over Pd_1.4Cu Decorated Oxygen Defective TiO_2-x Nanoarray for Electrocatalytic...

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 TiO_2-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.