Ultrathin Co0.5NiS Nanosheets for Hydrazine Oxidation Assisted Nitrite Reduction

Abstract Nitrite (NO 2 − ) and hydrazine (N 2 H 4 ) are common N‐pollutants in groundwater. The electrochemical method can realize the treatment of N‐pollutants and the synthesis of energy substance ammonia (NH 3 ). Designing and synthesizing efficient electrocatalysts is of great significance. Herein, ultrathin Co 0.5 NiS nanosheets attached on nickel foam (Co 0.5 NiS‐NSs/NF) are synthesized via cyanogel‐NaBH 4 hydrolysis process and succedent sulfurization approach. Owing to the ultrathin nanosheet structure and the interaction between Ni and Co, Co 0.5 NiS‐NSs/NF exhibits high activity for NO 2 − reduction reaction (NO 2 − RR), in which the Faraday efficiency is 92.2% and the NH 3 yield is 0.25 mmol h −1 cm −2 at −0.15 V potential. Meanwhile, Co 0.5 NiS‐NSs/NF also displays remarkable activity for N 2 H 4 oxidation reaction in KOH electrolyte. Therefore, a symmetrical Co 0.5 NiS‐NSs/NF||Co 0.5 NiS‐NSs/NF electrolyzer is assembled, which only needs the operating voltage of 0.36 V to reach 10 mA cm −2 for NO 2 − ‐to‐NH 3 conversion in the presence of N 2 H 4 . This work reports a promising and efficient strategy for NH 3 production at a small operating voltage and treatment of the N‐pollutants.