Combining soft electrode and ion exchange membranes for increasing salinity difference energy efficiency

Abstract A large variety of routes have been envisaged for improving the efficiency of methods aimed at producing clean, renewable energy. One of them includes the so-called capmix techniques, whereby clean electrical energy is obtained by alternately contacting salty and fresh solutions with capacitive electrodes. Investigations in this area have focused on optimizing materials, cycle implementation, up-scaling, and so on. One possibility that has been explored regards the use of ion exchange membranes for producing the necessary voltage differences between electrodes when in contact with concentrated and dilute ionic solutions. A related, but different approach consists in treating the electrodes with charged layers, notably polyelectrolytes. In this work, we propose an original combination of the two most efficient capmix techniques by simultaneously coating the carbon electrodes with membranes and polyelectrolytes. With the objective of analyzing the benefit of this new proposal in terms of energy and power, CAPMIX cycles were performed and carefully examined. These results will lead to the first insight into the ensemble behavior of polyelectrolyte layers and exchange membranes which will be key for the overall improvement of the CAPMIX methods.