Efficient Electroreduction of Nitrate into Ammonia at Ultralow Concentrations Via an Enrichment Effect

The electroreduction of nitrate (NO3-) pollutants to ammonia (NH3) offers an alternative approach for both wastewater treatment and NH3 synthesis. Numerous electrocatalysts have been reported for the electroreduction of NO3- to NH3, but most of them demonstrate poor performance at ultralow NO3- concentrations. In this study, a Cu-based catalyst for electroreduction of NO3- at ultralow concentrations is developed by encapsulating Cu nanoparticles in a porous carbon framework (Cu@C). At -0.3 V vs reversible hydrogen electrode (RHE), Cu@C achieves Faradaic efficiency for NH3 of 72.0% with 1 x 10(-3) m NO3-, which is 3.6 times higher than that of Cu nanoparticles. Notably, at -0.9 V vs RHE, the yield rate of NH3 for Cu@C is 469.5 mu g h(-1) cm(-2), which is the highest value reported for electrocatalysts with 1 x 10(-3) m NO3-. An investigation of the mechanism reveals that NO3- can be concentrated owing to the enrichment effect of the porous carbon framework in Cu@C, thereby facilitating the mass transfer of NO3- for efficient electroreduction into NH3 at ultralow concentrations.