Trimesic acid modified copper‑cobalt layered double hydroxide nanosheets boost electrocatalytic reduction of nitrate...

The electrocatalytic reduction of nitrate into valuable ammonia (NH₃) presents an environmentally friendly and sustainable strategy for the elimination of nitrate pollution and the synthesis of ammonia. Nevertheless, the activity and selectivity for ammonia production remain unsatisfactory, particularly at low applied negative potentials. Herein, we present the synthesis of layered double hydroxide (LDH) electrocatalysts featuring adjustable Cu/Co molar ratios and organic molecule trimesic acid (TA) modification, designated as Cu_xCo_1-x-LDH/TA (x = 0.75, 0.67, or 0.5), aiming to facilitate the electrochemical nitrate reduction reaction (NITRR). Intriguingly, the microstructure, crystalline form and electrical conductivity of LDH, are substantially modified by organic molecule TA with three carboxyl groups that play a pivotal role in bridging [M(OH)₆]^n-6 species (M = Cu or Co), thus facilitating the development of a conjugated two-dimensional layered framework. This conjugated, extended planar configuration augments the inherent conductivity, and ensures the uniform dispersion of copper and cobalt active sites on its surface, maximizing their synergistic effect during the NITRR. The resulting Cu_0.67Co_0.33 - LDH/TA exhibits a high NH₃ yield of 355.9 μmol·mg^-1·h^-1 and a Faradaic efficiency for NH₃ (FE_NH3) of 93.9 % for the NITRR, even at an extremely low applied negative potential of -0.6 V versus the reversible hydrogen electrode (vs RHE), which was significantly higher than that of pristine Cu_0.67Co_0.33 - LDH (55.0 μmol·mg^-1·h^-1 and 71.0 %, respectively). This work provides a significant reference for the utilization of organic molecules in modifying inorganic materials to boost electrocatalytic NITRR performance.