Activated TiO2 with tuned vacancy for efficient electrochemical nitrogen reduction

Renewable energy-driven electrochemical N 2 reduction reaction (NRR) provides a green and sustainable route for NH 3 synthesis under ambient conditions but is plagued by a high reaction barrier and low selectivity. To promote NRR, modification of the catalyst surface to increase N 2 adsorption and activation is key. Here, we show that engineering surface oxygen vacancies of TiO 2 permits significantly enhanced NRR activity with an NH 3 yield rate of about 3.0 μg NH3  h −1 mg cat. −1 and a faradaic efficiency (FE) of 6.5% at -0.12 V ( vs . the reversible hydrogen electrode, RHE). Efficient conversion of N 2 to NH 3 is achieved in a wide applied potential range from -0.07 to -0.22 V ( vs . RHE) with NH 3 production rates ≥ 2.0 μg NH3  h −1 mg cat. -1 and NH 3 FEs ≥ 4.9%, respectively. An NH 3 FE as high as 9.8% is obtained at a low overpotential of 80 mV. Density functional theory calculations reveal that the surface oxygen vacancies in TiO 2 play a vital role in facilitating electrochemical N 2 reduction by activating the first protonation step and also increasing N 2 chemisorption (relative to *H).