Enhanced electrocatalytic reduction of nitrate over a ternary alloy catalyst of CuPdFe: Structure, performance, and mechanism

From the perspectives of environmental protection and resource reclamation, the electrocatalytic reduction of nitrate not only removes nitrate but also converts it into value-added ammonia. In this study, a galvanostatic deposition method was used to prepare a dendrite-like CuNi substrate, on which Cu, Pd, and Fe were co-deposited by pulse electrodeposition to fabricate a ternary alloy electrode for the highly efficient reduction of nitrate to ammonia. The physicochemical properties of the synthesized materials were characterized in detail by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical tests. The results indicated that, benefiting from the dendritic substrate, the electrochemically active surface area of the ternary alloy electrode increased by 1.65 times. Under optimal conditions (applied potential −1.6 V (vs. SCE); pH 7), the removal efficiency of NO3--N (100 mg L−1) over the C3P1F1 electrode reached 98.9 % in 180 min. The selectivity of NH3-N and its yield were 83.1 % and 309.5 μg h−1 cm−2, respectively. The faradaic efficiency was 83.7 %. Based on the experimental results and theoretical calculations, it is believed that the enhanced adsorption of NO3- to the ternary alloy electrode surface is one of the reasons for the improvement in electrocatalytic nitrate reduction. In addition, * H-capturing experiments clarified the important role of *H in nitrate reduction. [Display omitted] •A dendritic CuNi substrate was used to prepare Cu, Pd, and Fe ternary alloy electrode.•The ECSA of C3P1F1 is 2.65 times that of the electrode with Cu sheet as the substrate.•Good performance on NRA was obtained for C3P1F1 with a low Pd load of 0.18 mg cm−2.•DFT calculations confirm the highest adsorption capacity of C3P1F1 for NO3-.•H-capturing experiments identify the important role of *H in nitrate reduction.