Atomic-Layer-Deposited Oxygen-Deficient TiO2 on Carbon Cloth: An Efficient Electrocatalyst for Nitrogen Fixation

Graphical Nitrogen fixation : Oxygen-vacancy-rich TiO 2 supported on carbon cloth (V-TiO 2 /CC) are prepared by atomic layer deposition technique coupled with annealing process, and used as a high-performance electrocatalyst for N 2 reduction to NH 3 . The as-obtained V-TiO 2 /CC shows a Faradaic efficiency as high as 31.6 % and a yield of 3.4 μg h −1 cm −2 in 0.5 M LiOH aqueous electrolyte. Electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the traditional Haber-Bosch process for ammonia production, but plagued by the high bonding energy of N≡N and the hydrogen evolution side reaction. Recent studies show that enhancing the adsorption and activation of N 2 on the catalyst is the key to improving the NRR performance, and the introduction of oxygen vacancies on the surface of metal oxides is an effective way to design high-performance catalysts. Here, TiO 2 with different thicknesses was deposited on conductive carbon cloth by atomic layer deposition, and then oxygen vacancies were introduced on the catalyst surface by an annealing process. The abundant oxygen vacancies on TiO 2 surface are found to be beneficial for enhancing the NRR activity of the catalysts. Moreover, the NRR activity is significantly influenced by the thickness of the deposited TiO 2 layer, and an over-thick TiO 2 layer leads to a decrease in the conductivity of the catalysts and hinders the charge transfer process. With the optimum thickness, the atomic-layer-deposited oxygen-deficient TiO 2 catalysts can achieve a Faradaic efficiency of 31.6 % and a yield of 3.4 μg h −1 cm −2 for ammonia production in 0.5 M LiOH aqueous electrolyte at 0 vs. RHE. It is anticipated that ultrathin semiconducting oxide catalysts synthesized by atomic layer deposition will have broad and promising applications for efficient electrochemical NRR. Introduction