In situ growth of copper/reduced graphene oxide on graphite surfaces for the electrocatalytic reduction of nitrate

A fast and simple electrochemical method was developed to make composite electrodes containing monodispersed copper nanoparticles (Cu NPs) and reduced graphene oxide (rGO) for nitrate removal. The Cu/rGO/graphite plate (GP) electrodes were fabricated after in situ electrochemical exfoliation and a one-step simultaneous graphene oxide (GO) reduction and Cu deposition. Bulk electrolysis results showed the percentage of nitrate removal up to 96.8% after 3 h and the reaction rate constant of the Cu/rGO/GP electrode was 14.08, 8.00 and 1.94 times higher than those of GP, GO/GP and Cu/GP electrodes, respectively. Further analysis revealed improvements in electron transfer, adsorption of the electroactive species and electrochemically active surface area, which all contributed to the enhancement of electrocatalytic nitrate reduction. Furthermore, the mechanism of nitrate reduction with the Cu/rGO/GP electrode was studied in detail by cyclic voltammetry. The voltammogram profile of the Cu/rGO/GP electrode after 50 scanning cycles was similar to that of the initial cycle, and the percentage of nitrate removal was still at 92.4% after the eighth application, demonstrating the high stability of the composite electrode. Taking together, results showed the promising application of graphene-based electrodes with copper nanoparticles in electrocatalytic denitrification.