Functionalized carbon nanotubes tape for energy harvesting from salinity gradients through asymmetric capacitive mixing

In this work, we investigated the possibility of using a commercial tape entirely made of continuous carbon nanotubes (CNTs) for blue energy harvesting application. The tape was used to build the electrodes of a device harvesting energy from salinity gradient based on the capacitive mixing (CapMix) technique. The tape was used as it is or functionalized to enhance its storage properties and to obtain an asymmetric device. The electrodes underwent a full set of electrochemical characterizations to test the impact of the functionalization. Thanks to high electrical conductivity, remarkable specific capacitance and good chemical stability, the tape acted both as active material and current collector, eliminating the need for metallic current collectors, reducing the mass of the system and avoiding possible corrosion of the metals due to close contact with saline solutions. This approach provided a simple and easily scalable device able to produce electrical power from the mixing of two solutions at different salinities. The achieved power output stands at 75 μW m−2 in artificial seawater/freshwater and 1.2 mW m−2 in artificial Mediterranean brine/seawater. These results contribute to the broader understanding of energy harvesting from salinity gradients, extending the technological application of CNT tape across the renewable energy field.