Multimetallic catalysts with rich oxygen vacancies for efficient reduction of nitrate to ammonia

The escalating levels of nitrate (NO3-) from industrial and agricultural activities have caused significant water pollution and eutrophication, threatening ecosystems and human health. Copper-based catalysts are preferred for converting NO3- to ammonia (NH3) because of their cost-effectiveness and high NO3- reduction activity. However, the NO3- reduction reaction faces the challenge of competing with the hydrogen evolution reaction (HER) and is prone to by-products such as nitrites (NO2-), resulting in low NH3 yield and poor selectivity. To further convert NO2- to NH3 with high Faradaic efficiency (FE), high yield, and high selectivity, we present Zn-doped Cu2O (Zn/Cu2O), offering an environmentally friendly substitute for the Haber-Bosch process. The Zn/Cu2O catalyst, synthesized through electrodeposition and high-temperature calcination, achieves a high FE of NH3 (90.74%) at -1.2 V vs. RHE. The by-product NO2- production is inhibited with a very low FE of 5.40%. The further incorporation of Au and Pd on the catalyst surface significantly boosts NH3 yield (1.12 mmol h-1 cm-2), demonstrating the potential for efficient and sustainable electrocatalytic NO3- reduction.