Ti₂O₃ Nanoparticles with Ti³⁺ Sites toward Efficient NH₃ Electrosynthesis under Ambient Conditions

Electrocatalytic nitrogen reduction reaction (NRR) enabled by introducing Ti³⁺ defect sites into TiO₂ through a doping strategy has recently attracted widespread attention. However, the amount of Ti³⁺ ions is limited due to the low concentration of dopants. Herein, we propose Ti₂O₃ nanoparticles as a pure Ti³⁺ system that performs efficiently toward NH₃ electrosynthesis under ambient conditions. This work has suggested that Ti³⁺ ions, as the main catalytically active sites, significantly increase the NRR activity. In an acidic electrolyte, Ti₂O₃ achieves extraordinary performance with a high NH₃ yield and a Faradaic efficiency of 26.01 μg h^-1 mg^-1 cat. and 9.16%, respectively, which are superior to most titanium-based NRR catalysts recently reported. Significantly, it also demonstrates a stable NH₃ yield in five consecutive cycles. Theoretical calculations uncovered that the enhanced electrocatalytic activity of Ti₂O₃ originated from Ti³⁺ active sites and significantly lowered the overpotential of the potential-determining step.