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

The electrocatalytic nitrate reduction reaction (NO 3 RR) has emerged as a promising strategy for ammonia (NH 3 ) synthesis under ambient conditions. However, the sluggish anodic oxygen evolution reaction (OER) not only significantly restricts the overall efficiency of the NO 3 RR 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 NO 3 RR at the cathode and organic pollution degradation at the anode. Specifically, Cu 2 Co 1 -LDH nanosheets exhibit an exceptional NH 3 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 Cu 4 Co 1 -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 Cu 1 Co 1 -LDH. Ultimately, the Cu 2 Co 1 -LDH cathode and Cu 4 Co 1 -LDH anode were coupled to form an asymmetric NO 3 RR||DOR bifunctional system that maintains a high NH 3 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 NO 3 RR||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 NO 3 RR and a strategy for asymmetric coupling with the degradation of organic pollutants.