Identifying the Origin of Ti Activity toward Enhanced Electrocatalytic N Reduction over TiO Nanoparticles Modulated by Mixed-Valent Copper.

The ambient electrocatalytic N reduction reaction (NRR) enabled by TiO has attracted extensive recent attention. Previous studies suggest the formation of Ti in TiO can significantly improve the NRR activity, but it still remains unclear what kinds of Ti are effective. Herein, it is demonstrated that mixed-valent Cu acts as an effective dopant to modulate the oxygen vacancy (V ) concentration and Ti formation, which markedly improves the electrocatalytic NRR performance. In 0.5 m LiClO , this electrocatalyst attains a high Faradic efficiency of 21.99% and a large NH yield of 21.31 µg h mg at -0.55 V vs reversible hydrogen electrode, which even surpasses most reported Ti-based NRR electrocatalysts. Using density function theory calculations, it is evidenced that mixed-valent Cu ions modulate the TiO (101) surface with multiple oxygen vacancies, which is beneficial for generating different Ti 3d defect states localized below the Fermi energy. N activation and adsorption are effectively strengthened when Ti 3d defect states present the splitting of e and t orbitals, which can be modulated by its coordination structure. The synergistic roles of the three ion pairs formed by the V defect, including Cu -Ti , Ti -Ti and Ti -Ti , are together responsible for the enhanced NRR performance.