Blue energy harvesting: development of supercapacitor devices with CNT-based electrodes for CapMix applications

In the next few decades, the world needs new energy sources to face population growth and increasing energy demand. Furthermore, these new energy sources must be renewable and sustainable in order to replace fossil energy. A good example can be the “blue energy”, an energy that can be harvested from the salinity difference of two solutions, the so-called “Salinity Gradient Power” (SPG). In particular, Capacitive Mixing (CapMix) is a SGP technique that recovers energy by cyclically injecting high and low salinity water in a cell. The aim of this thesis is to demonstrate that CapMix can be performed using carbon nanotubes (CNTs) based electrodes in a supercapacitor device with NaCl solutions. Electrochemical characterizations are performed on a CNTs tape. The potential rise of the CNTs is measured when high salinity solution is replaced by low salinity solution at different applied potentials. Different functionalization procedures were investigated to tune the properties of the CNTs. The CapMix cycle is performed in a cell with the best performing electrodes. Currents and voltages are measured in each cycle and an evaluation of energy density and power density is obtained. The measurements conducted show that energy production is possible using CNTs electrodes and NaCl solutions. Future research should be focused on optimizing this technique to maximize power production.