Characterization of ion exchange membranes for energy harvesting and storage devices

The energy demand in the world is growing day by day, providing continuously new challenges in the way of production. All the systems of connections and storage are investigated too. A smart and very useful solution to supply to needs for off-grid and compact situations, accompanied also by low losses, is represented by integrated Harvest and Storage (HS) devices. Many types of them exist, based on the integration of energy harvest devices, like DSSC and storage ones, like supercapacitors. In this work, many configurations have been studied and compared. They were distinguished according to their main components (DSSC, OPC, PVS or Si-PVC and supercapacitors, batteries or RFB) and their geometry (planr vs. fiber-shaped or depending on number of electrodes). HS devices have also the great advantage to be an eco-friendly solution, being born to be realized with only renewable sources. In order to build a device like the one made of DSSC and supercapacitor, a good component to keep redox mediators of DSSCs confined, is represented by Ion Exchange Membranes (IEMs). These components are necessary since the mediator can lead to reactions on storage device electrodes, making them to self-discharge. In this work, a PEM membrane (Nafion®) has been studied. Particular attention has been made on the use of platinum microelectrodes. Their polishing procedures were determined and reported. They were used since they allowed to find a limiting current in cyclic voltammetry. This current was connected to diffusion coefficient of the redox mediator. By determining it, it was possible to have the mediator concentration in an unknown solution. This technique has been used to determine membrane efficiency, according to future employment in a real device. Further tests were conducted on the membrane, like permselectivity and water uptake, in order to have a complete view. Every method used, gave really good results (efficiencies of more than 99% after a week were recovered). For this reason, it was possible to affirm that the Nafion® membrane was a good one in integration of HS devices. The redox mediator used in this work was potassium hexacyanoferrate(III) (K3Fe(CN)6). Proofs of the effect of redox shuttling have been found and used to confirm the need for a solution to keep redox mediator separated from the supercapacitor.