Highly efficient electrochemical reduction of nitrate to ammonia on cobalt doped Ti3C2 MXene nanosheets

The discharge of large amounts of industrial wastewater and waste residue in industry and agriculture can lead to a continuous increase in nitrate concentration in groundwater, causing pollution of water resources. Currently, there is an urgent need for an efficient catalyst for nitrate reduction. This article analyzed the performance of Co doped Ti3C2 mxenes composites (Co-Ti3C2) electrodes for reducing nitrate, and summarized the possible pathways for reducing nitrate to synthesize ammonia through theoretical calculations. In the experimental section, Co-Ti3C2 was successfully prepared by the hydrothermal method. Electrochemical experiments were conducted in a mixed electrolyte of 0.5 mol·L-1 Na2SO4 solution and 0.05 mol·L-1 NaNO3 solution. The results showed that the Co-Ti3C2 exhibited considerable long-term stability in the nitrate electrochemical reduction reaction (NITRR) at −0.55 V (VS. RHE) under mild environmental conditions, with an ammonia yield of 102.06 mg·h−1·mg−1, the Faraday efficiency (FE) of 50.9 %, and a slope of 102.06 mV·dec-1 for Tafel. The maximum yield at −0.95 V (VS. RHE) was 208.5 mg·h−1·mg−1, with FE of 66.8 %. The free energy diagram of Co-Ti3C2 was calculated using density functional theory, indicating that surface Co plays a crucial role in improving the catalytic activity of Ti3C2 materials. This work provided a feasible strategy for designing more efficient MXene-based electrocatalysts.