Identifying the Origin of Ti3+ Activity toward Enhanced Electrocatalytic N2 Reduction over TiO2 Nanoparticles Modulated by Mixed-Valent Copper

The ambient electrocatalytic N(2)reduction reaction (NRR) enabled by TiO(2)has attracted extensive recent attention. Previous studies suggest the formation of Ti(3+)in TiO(2)can significantly improve the NRR activity, but it still remains unclear what kinds of Ti(3+)are effective. Herein, it is demonstrated that mixed-valent Cu acts as an effective dopant to modulate the oxygen vacancy (V-O) concentration and Ti(3+)formation, which markedly improves the electrocatalytic NRR performance. In 0.5mLiClO(4), this electrocatalyst attains a high Faradic efficiency of 21.99% and a large NH(3)yield of 21.31 mu g h(-1)mg(cat.)(-1)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 TiO2(101) surface with multiple oxygen vacancies, which is beneficial for generating different Ti(3+)3d(1)defect states localized below the Fermi energy. N(2)activation and adsorption are effectively strengthened when Ti(3+)3d(1)defect states present the splitting of e(g)and t(2g)orbitals, which can be modulated by its coordination structure. The synergistic roles of the three ion pairs formed by the V(O)defect, including Cu1+-Ti4+, Ti3+-Ti(4+)and Ti3+-Ti3+, are together responsible for the enhanced NRR performance.