High-Efficiency Ammonia Electrosynthesis on Anatase TiO<sub>2–<i>x</i></sub> Nanobelt Arrays with Oxygen Vacancies by Selective Reduction of Nitrite
Zhaofei Ren, Qiuyue Chen, Xuguang An, Qian Liu, Lisi Xie, Jing Zhang, Weitang Yao, Mohamed S. Hamdy, Qingquan Kong, Xuping Sun
Abstract
Electrocatalytic reduction of nitrite to NH3 provides a new route for the treatment of nitrite in wastewater, as well as an attractive alternative to NH3 synthesis. Here, we report that an oxygen vacancy-rich TiO2–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/H2 atmosphere. Anatase TiO2–x (A-TiO2–x) can be a superb catalyst for the efficient conversion of NO2– to NH3; a high NH3 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 NaNO2 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–NO2– battery with such A-TiO2–x as a cathode delivers a power density of 2.38 mW cm–2 as well as a NH3 yield of 885 μg h–1 cm–2.