Preparation of a novel Cu-Sn-Bi cathode and performance on nitrate electroreduction

Cu-Sn-Bi layer coated on Ti substrate was prepared using electrodeposition method and applied as cathode material for electrochemical reduction of nitrate in this research. Linear sweep voltammetry (LSV), chronoamperometry (CA), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) were used to scrutinize the electrochemical performance and the cathode materials. LSV results illustrated that Cu-Sn-Bi cathode possessed the ability for nitrate reduction. Preparation conditions including deposition time, current density, temperature and the content of Bi were optimized based on NO₃ ^-N removal and byproducts selectivity. Results showed that the cathode with Bi content of 3.18 at.%, and electrodepositing at current density of 6 mA cm^-2, 35 °C for 30 min achieved the best performance during the experiment. The increase of Bi content could improve the electrocatalytic activity and stability of the cathode. Compared with other common researched cathodes (Cu and Fe), Cu-Sn-Bi (3.18 at.%) exhibited better performance, i.e. the highest NO₃ ^-N removal of 88.43% and the selectivity of harmless N₂ was 77.80%. The kinetic studies showed that the reduction of nitrate on Cu-Sn-Bi followed pseudo-first-order kinetics.