In-situ electrochemical flue gas desulfurization via carbon black-based gas diffusion electrodes: Performance, kinetics and mechanism

Electrochemical flue gas desulfurization technology has received much attention in recent years due to its good performance and environmental friendliness. However, there are still demands in energy efficiency enhancement and cost reduction. In this study, carbon black-based gas diffusion electrodes (GDEs) are used to produce H2O2 via oxygen reduction reaction (ORR) for in-situ oxidation of SO2 to SO42- in an electrolysis system. The effect of multi-walled carbon nanotubes (MWCNTs) and activated carbon (AC) as minor additive in the catalytic layers of GDEs is investigated. The results show that the MWCNTs play a positive role depending on its electrocatalysis for 2e-ORR, electron-bridge action and mesopore structure, giving the highest H2O2 production (1002.4 mg L-1), SO2 removal efficiency (98.0%) and reaction kinetics (0.52 mM min(-1)) and the lowest energy consumption (1.7 kW h kg(-1)) among the three GDEs. While the AC is adverse to the SO2 removal due to its excessive porous structure and catalysis on H2O2 reduction. The GDEs may be poisoned by SO32- or SO42- adsorption on active sites as sudden power failure and long-time running, but it can be restored by conducting only ORR, indicating great potential in industrial application. (C) 2016 Published by Elsevier B.V.