Structural optimization of oxygen vacancies in WO3 by Cu doping for enhanced electrocatalytic nitrate reduction to ammonia

Electrochemical nitrate reduction to ammonia can not only remove harmful nitrate pollutants from wastewater but also generate valuable ammonia. In this paper, a simple hydrothermal method was used to successfully synthesize the nanorod-shaped Cu-WO3 catalyst, demonstrating excellent NO3RR performance. Experimental results indicate that Cu-doped WO3 significantly increases the content of oxygen vacancies compared to the sample of WO3, resulting in improved NO3RR performance. As a result, Cu-WO3 exhibits high yield of NH3 is 2131.3 μg/h/mgcat and Faraday efficiency is 94% at optimum potential of −0.6 V (vs. RHE) in an alkaline electrolyte. 15N isotopic labeling tests confirm the origin of produced ammonia. Cu-WO3 also exhibits excellent electrochemical cycle stability and long-term durability, suggesting it possible application in industrial filed. In situ Fourier-transform infrared (FTIR) spectroscopy reveals that Cu-WO3 can effectively adsorb nitrate and nitrogen dioxide intermediates. This work provided valuable insights for the exploration of efficient nitrate NO3RR electrocatalysts.