High-Efficiency Ammonia Electrosynthesis on Anatase TiO 2- x Nanobelt Arrays with Oxygen Vacancies by Selective Reduction of Nitrite.

Electrocatalytic reduction of nitrite to NH 3 provides a new route for the treatment of nitrite in wastewater, as well as an attractive alternative to NH 3 synthesis. Here, we report that an oxygen vacancy-rich TiO 2- x nanoarray with different crystal structures self-supported on the Ti plate can be prepared by hydrothermal synthesis and by subsequently annealing it in an Ar/H 2 atmosphere. Anatase TiO 2- x (A-TiO 2- x ) can be a superb catalyst for the efficient conversion of NO 2 - to NH 3 ; a high NH 3 yield of 12,230.1 ± 406.9 μg h -1 cm -2 along with a Faradaic efficiency of 91.1 ± 5.5% can be achieved in a 0.1 M NaOH solution containing 0.1 M NaNO 2 at -0.8 V, which also exhibits preferable durability with almost no decay of catalytic performances after cycling tests and long-term electrolysis. Furthermore, a Zn-NO 2 - battery with such A-TiO 2- x as a cathode delivers a power density of 2.38 mW cm -2 as well as a NH 3 yield of 885 μg h -1 cm -2 .