Dopant‐Induced Electronic States Regulation Boosting Electroreduction of Dilute Nitrate to Ammonium

Electrochemically converting NO3- into NH3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO3- is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO3- reduction reaction (NO3 RR) with dilute NO3- concentration (≤100 ppm NO3- -N). Notably, a linear relationship was established by plotting NH3 yield vs. the oxidation state of Cu, indicating that the increase of Cu+ content leads to an enhanced NO3- -to-NH3 conversion activity. Under a low NO3- -N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO3- -to-NH3 conversion at -0.55 to -0.6 V vs. RHE, and a record-high NH3 yield of 309 mmol h-1 gcat-1 , which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h-1 gcat-1 ). This research provides an effective method for conversion of dilute NO3- to NH3 , which has certain guiding significance for the efficient and green conversion of wastewater in the future.