Self-growing nitrogen doped cobalt-copper Co4Cu1N-CN/CF electrode for electrochemical nitrate removal.

Selective electrochemical nitrate reduction reaction to nitrogen gas (NO 3 -N 2 RR) has emerged as a promising strategy. Herein, a self-growing Co 4 Cu 1 N-CN/CF composite electrode was successfully fabricated as cathode for electrochemical nitrate reduction reaction to ammonia (NO 3 -NH 3 RR) with the high NH 4 ⁺-N selectivity (S NH4 ⁺ -N over 97.8%), which coupled with IrO 2 -RuO 2 /Ti anode via hyperchlorination for NO 3 -N 2 RR (R TN over 96.1%). Electrochemical and quenching experiments indicated that direct electron transfer (DET) took precedence over indirect reduction (the surface-adsorbed H*) in NO 3 -NH 3 RR: Cu sites favored the nitrate to nitrite, and Co sites made for the subsequent reduction to ammonia. Furthermore, the high electron transfer number (n) demonstrated that the excellent performance of Co 4 Cu 1 N-CN/CF cathode was attributed to the predominance of DET form NO 3 ^－to NH 4 ⁺ by skipping over some intermediate pathway. This study deepened the understanding of one-step electron reduction in the bimetal synergic NO 3 -NH 3 RR reduction and this electrochemical system has practically potential to treat nitrate wastewater efficiently. [Display omitted] • The binderless Co 4 Cu 1 N-CN/CF was fabricated by self-growth of Co/Cu on carbon felt. • The NO 3 ^－-N removal of Co 4 Cu 1 N-CN/CF attained 97.2 % with 97.8 % selectivity to NH 4 ⁺-N. • Cu and Co sites favored the reduction of nitrate to nitrite and nitrite to ammonia, respectively. • Excellent electrocatalytic activity was related with skipping many intermediate reaction. [ABSTRACT FROM AUTHOR]