Enhanced electrocatalytic nitrate reduction via carbon material integration between Cu and Ni-foam: Mechanisms and performance analysis

[Display omitted] •Developed novel Cu@CNFs/NF, Cu@CNTs/NF, Cu@CB/NF electrodes, achieving 98% RNO3-.•Cu@CNFs/NF demonstrated superior N2 selectivity of 51% under optimized conditions.•Increased mesoporosity and surface area improved NO3–-N removal and N2 selectivity.•Cu@CNFs/NF maintained a 97% RNO3- after 10 cycles, confirming electrode stability. This study investigates the electrocatalytic reduction of nitrates using three novel electrodes: Cu@CNFs/NF, Cu@CNTs/NF, and Cu@CB/NF, synthesized via an impregnation-calcination-electrodeposition technique. The emphasis is on the role of different carbon materials, which serve as the base or matrix for Cu, and their influence on nitrate reduction and nitrogen selectivity. Experimental results indicated that all three-electrode variants outperformed the conventional Cu/NF electrode in nitrate reduction and nitrogen selectivity. Among these, the Cu@CNFs/NF electrode emerged as the standout performer, achieving an impressive nitrate reduction rate of up to 98 % and a nitrogen selectivity of 51 % under the optimized experimental conditions (pH 7, nitrate concentration of 100 mg∙L-1 as NO3–-N, a current density of 8 mA cm−2, a sodium sulfate concentration of 0.5 g∙L-1, 120 min, anode: Ti/RuO2-IrO2). Stability tests confirmed that the Cu@CNFs/NF electrode maintained over 97 % nitrate removal efficiency across ten cycles, highlighting its robustness and potential for practical water treatment applications. A significant enhancement in nitrogen selectivity of Cu@CNFs/NF to 96 % was observed when using 0.75 g∙L-1 NaCl as the electrolyte during an extended electrolysis period of 180 min, underscoring its potential to optimize catalytic efficiency. Characterization data from SEM, XRD, and other analyses substantiate that the incorporation of carbon materials augments the active sites of copper; Nitrogen adsorption–desorption experiments further illustrate that the integration of carbon materials leads to an increase in mesoporous volume. This increase promotes adsorptive interactions, enhances the conversion of intermediates, and contributes to the improvement of nitrate reduction and nitrogen selectivity. These results highlight the potential of tailored carbon material integration for enhancing the electrocatalytic performance of electrodes in practical water treatment applications.