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  g_cat ^-1 , which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h^-1  g_cat ^-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.