Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst

Nitrate, a common pollutant in wastewater and groundwater, has been efficiently converted into valuable ammonia products via an electrochemical method using Ru-dispersed Cu nanowire as the catalyst. Electrochemically converting nitrate ions, a widely distributed nitrogen source in industrial wastewater and polluted groundwater, into ammonia represents a sustainable route for both wastewater treatment and ammonia generation. However, it is currently hindered by low catalytic activities, especially under low nitrate concentrations. Here we report a high-performance Ru-dispersed Cu nanowire catalyst that delivers an industrial-relevant nitrate reduction current of 1 A cm(-2) while maintaining a high NH3 Faradaic efficiency of 93%. More importantly, this high nitrate-reduction catalytic activity enables over a 99% nitrate conversion into ammonia, from an industrial wastewater level of 2,000 ppm to a drinkable water level <50 ppm, while still maintaining an over 90% Faradaic efficiency. Coupling the nitrate reduction effluent stream with an air stripping process, we successfully obtained high purity solid NH4Cl and liquid NH3 solution products, which suggests a practical approach to convert wastewater nitrate into valuable ammonia products. Density functional theory calculations reveal that the highly dispersed Ru atoms provide active nitrate reduction sites and the surrounding Cu sites can suppress the main side reaction, the hydrogen evolution reaction.

Automated summary

The research team has efficiently converted nitrate, a common pollutant in wastewater and groundwater, into valuable ammonia products using a Ru-dispersed Cu nanowire catalyst through electrochemical methods. This sustainable approach not only treats wastewater but also generates ammonia, but current low catalytic activities pose challenges. However, the team has developed a high-performance catalyst that achieves over 99% nitrate conversion into ammonia and successfully obtains high purity NH4Cl solid and NH3 liquid products.