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

Abstract

AbstractNitrite (NO2−) and hydrazine (N2H4) are common N‐pollutants in groundwater. The electrochemical method can realize the treatment of N‐pollutants and the synthesis of energy substance ammonia (NH3). Designing and synthesizing efficient electrocatalysts is of great significance. Herein, ultrathin Co0.5NiS nanosheets attached on nickel foam (Co0.5NiS‐NSs/NF) are synthesized via cyanogel‐NaBH4 hydrolysis process and succedent sulfurization approach. Owing to the ultrathin nanosheet structure and the interaction between Ni and Co, Co0.5NiS‐NSs/NF exhibits high activity for NO2− reduction reaction (NO2−RR), in which the Faraday efficiency is 92.2% and the NH3 yield is 0.25 mmol h−1 cm−2 at −0.15 V potential. Meanwhile, Co0.5NiS‐NSs/NF also displays remarkable activity for N2H4 oxidation reaction in KOH electrolyte. Therefore, a symmetrical Co0.5NiS‐NSs/NF||Co0.5NiS‐NSs/NF electrolyzer is assembled, which only needs the operating voltage of 0.36 V to reach 10 mA cm−2 for NO2−‐to‐NH3 conversion in the presence of N2H4. This work reports a promising and efficient strategy for NH3 production at a small operating voltage and treatment of the N‐pollutants.