CuCo Layered Double Hydroxide Nanosheet-Based Electrocatalysts for Asymmetric Coupled Nitrate Reduction to Ammonia and Dichlorophenol Degradation

The electrocatalytic nitrate reduction reaction (NO3RR) has emerged as a promising strategy for ammonia (NH3) synthesis under ambient conditions. However, the sluggish anodic oxygen evolution reaction (OER) not only significantly restricts the overall efficiency of the NO3RR process, but also inevitably wastes electrical energy. In this study, we synthesized a series of CuCo layered double hydroxide (LDH) nanosheets by adjusting the Cu/Co ratio, which demonstrate enhanced electrocatalytic activity for the NO3RR at the cathode and organic pollution degradation at the anode. Specifically, Cu2Co1-LDH nanosheets exhibit an exceptional NH3 yield of 0.32 mmol h–1 cm–2 and a high Faradaic efficiency (FE) of 82.24% at −1.0 V vs reversible hydrogen electrode (RHE). Meanwhile, the optimized Cu4Co1-LDH nanosheets achieve highly efficient 2,4-dichlorophenol (2,4-DCP) oxidation reaction (DOR) at 1.9 V vs RHE, which is 1.5 times higher than that of the Cu1Co1-LDH. Ultimately, the Cu2Co1-LDH cathode and Cu4Co1-LDH anode were coupled to form an asymmetric NO3RR||DOR bifunctional system that maintains a high NH3 yield and 2,4-DCP degradation at a current density of 10 mA cm–2 under a cell voltage of 1.89 V, 230 mV lower than that of the NO3RR||OER arrangement. A series of electrochemical tests reveal that the excellent electrocatalytic performance of the CuCo-LDH nanosheets stems from the bimetallic synergy and layered nanostructure, which effectively inhibit the competing reactions and enhance the charge-transfer efficiency. This study demonstrates an effective design for bifunctional nanocatalysts to address the kinetic sluggishness in the NO3RR and a strategy for asymmetric coupling with the degradation of organic pollutants.