WO2 nanoparticles with oxygen vacancies: a high-efficiency electrocatalyst for the conversion of nitrite to ammonia

Electrocatalytic reduction of nitrite (NO2-) is considered an effective method to solve its environmental pollution issue as well as sustainable ammonia (NH3) synthesis under ambient conditions but still requires high-performance catalysts. Herein, self-supported monoclinic WO2 nanoparticles with abundant oxygen vacancies (OVs) on a tungsten plate (WO2/W) are demonstrated as a highly efficient electrocatalyst for selectively reducing NO2- to NH3. In 0.1 M NaOH solution containing 0.1 M NO2-, such an electrocatalyst achieves an excellent yield of 14 964.25 +/- 826.06 mu g h(-1) cm(-2) and high faradaic efficiency (FE) of 94.32 +/- 1.15% at -0.9 V. Remarkably, the assembled Zn-NO2- battery delivers a high power density of 5.05 mW cm(-2) and simultaneously offers an abundant NH3 yield of 1923.88 mu g h(-1) cm(-2). Theoretical calculations reveal the critical role of OVs for WO2 in the nitrite electrocatalytic reduction process and its possible reaction pathway.