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

Abstract

Selective electrochemical nitrate reduction reaction to nitrogen gas (NO3-N2RR) has emerged as a promising strategy. Herein, a self-growing Co4Cu1N-CN/CF composite electrode was successfully fabricated as cathode for electrochemical nitrate reduction reaction to ammonia (NO3-NH3RR) with the high NH4+-N selectivity (SNH4+-N over 97.8%), which coupled with IrO2-RuO2/Ti anode via hyperchlorination for NO3-N2RR (RTN over 96.1%). Electrochemical and quenching experiments indicated that direct electron transfer (DET) took precedence over indirect reduction (the surface-adsorbed H*) in NO3-NH3RR: 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 Co4Cu1N-CN/CF cathode was attributed to the predominance of DET form NO3－to NH4+ by skipping over some intermediate pathway. This study deepened the understanding of one-step electron reduction in the bimetal synergic NO3-NH3RR reduction and this electrochemical system has practically potential to treat nitrate wastewater efficiently.