High-Performance Asymmetric Flow-Electrode Capacitive Mixing with MnO2-CoatedActivated Carbon Flow-Electrode for Energy Harvesting from Salinity Gradient Power

Abstract

Flow-electrode capacitive mixing (F-CapMix) is apromising energy harvesting system, utilizing the salinitygradient difference between seawater and river water. However,the conventional F-CapMix system has a low power density dueto the limited charge storage of porous carbon materialsthrough the electrical double layer. In this study, wefirst reportmanganese dioxide-coated activated carbon (MO@AC) as aflow-electrode material for the F-CapMix system. MnO2nanoparticles could be easily decorated on the surface ofactivated carbon (AC) by the reduction of KMnO4in an acidicmedium. We systematically study electrochemical properties of AC and MO@AC-basedflow-electrodes as positive andnegative electrodes for both symmetric and asymmetric F-CapMix systems. The asymmetric F-CapMix system employing theMO@ACflow-electrode exhibits an outstanding power density of 2.22 W/m2through the reversible redox reaction with Na+ions. Our strategies can be extended to other materials that have redox reactions with Na+and Cl-ions for the F-CapMixsystem.