Nitrate Electrochemical Reduction Using Modified Boron- Doped Diamond Electrode from Copper Electroless

Abstract

Modified boron- doped diamond (BDD) electrodes from copper (Cu) electroless process were produced and characterised aiming their application at nitrate electrochemical removal. Cu deposits on BDD surface may promote its conductivity and selectivity increase mainly for nitrate ions reduction using the flow electrochemical reactor. Cu/BDD composites were obtained with optimised parameters to produce high- quality electrodes in suitable doping level associated with Cu particle deposits. BDD films were grown on titanium (Ti) substrates from hot filament chemical vapour deposition reactor. Higher deposit density as well as better Cu particles uniformity was observed for the highest doped BDD electrodes. Considering the nitrate reduction, four cathode and four anode electrodes with 2.5 × 2.5 cm2 were necessary for each electrolysis. The experiments were carried out by varying current density, reactor flow rate, and supporting electrolyte. The process effectiveness was analysed as a function of BDD/Ti and/or Cu/BDD/Ti electrodes as cathode where the results were monitored by Ion Chromatography. This analyses showed the highest electrolysis efficiency for 300 L h-1 flow rates, when BDD/Ti electrodes were used both as an anode and as cathode simultaneously. These results were corroborated by X-ray photoelectron spectroscopy (XPS) measurements for electrode surfaces before and after the electrolysis. This behaviour may be associated with the lower impurity adsorption on the film surface due to the turbulent regime used in the flow reactor. On the other hand, when Cu/BDD/Ti was used as a cathode, the best efficiency was obtained for the flow rate of 50 L h-1, which may be associated to the low hydrogen adsorption on the electrode surface due to the Cu presence.