No abstract

In this study, the degradation of Methylene Blue (MB) dye accompanied with the reduction of CO2 was performed in an electrochemical (EC) process by using carbon nanotubes grown on carbon fiber (CNTs/CFM) electrodes as the cathode and anode in a two-compartment electrochemical cell. The growth of CNTs on CFM via chemical vapor deposition led to the significant improvement in physicochemical properties of CNTs/CFM which were beneficial for the EC process. The effects of various operating parameters including supporting electrolytes (KHCO3 and H2SO4), initial concentration of MB (5, 10, 15 and 20 mg L− 1) and applied currents (10, 50 and 100 mA) on the degradation of MB were investigated. The results confirmed the vital influence of applied current and initial concentration of MB while the supporting electrolytes played a minor role in MB degradation. On the contrary, the influence of electrolytes in the performance of CO2 reduction was more significant on the production and selectivity of generated products. The optimal electrochemical system included 0.1 M KHCO3 as the electrolyte and an applied current of 50 mA in anodic cell and CO2 saturated solution in cathodic cell; such a system resulted in the EC degradation efficiency of 72% at the MB initial concentration of 10 mg L− 1 in the anodic cell and production of 4.7 mM cm− 2 CO, 67 mM cm− 2 H2, and 11.3 mg L− 1 oxalic acid in the cathodic cell corresponding to the Faradaic efficiencies of 28, 40 and 4%, respectively. The results of reusability test deduced that the stability of CNTs/CFM was still satisfactory after 4 runs. The results of this study demonstrated the good applicability of CNTs/CFM to be simultaneously used the electrodes for the EC oxidation of dye and the EC reduction of CO2 to obtain valuable compounds.

No abstract

Simultaneous degradation of methylene blue (MB) and reduction of CO2 by electrochemical process using CNTs/CF electrodes have been performed in various supporting electrolytes and applied current conditions in this study. The CNTs/CF electrodes have been successfully synthesized by chemical vapor deposition (CVD) method and employed as both cathode and anode in a two-compartment electrochemical cell. The synthesized electrodes were characterized by SEM and FTIR. The electrochemical oxidation efficiency of CNTs/CF electrodes in the anodic cell was evaluated using MB as model compound under electrolytes of H2SO4 and KHCO3 and applied currents of 10, 50 and 100 mA. The electrochemical reduction activity of CNTs/CF electrodes in the cathodic cell was assessed by the conversion of CO2 into CO and oxalic acid, and the generation of H2 under electrolytes of Na2SO4 and KHCO3 and a fixed applied current of 50 mA. The degradation kinetics of MB followed the pseudo-first-order model and the degradation efficiency was significantly affected by applied current rather than the sort of electrolyte under optimum condition. The optimal applied current can promote the high enough production of oxidant but also avoid electrode damage. The synthesized electrode of CNTs/CF combined with the electrochemical systems developed in this study provide a good solution for the simultaneous electrochemical oxidation of organic pollutants and reduction of CO2 to CO to yield H2 and CO, in which reaches the dual benefits of reduction of environmental hazards and production of green energy.