Towards sustainable solid-state supercapacitors: Electroactive conducting polymers combined with biohydrogels

Solid-state organic electrochemical supercapacitors (OESCs) have been fabricated using poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes, a biohydrogel as electrolyte system, and polyaniline fibers as redox additive. The effectivity of sodium alginate, κ-carrageenan, chitosan and gelatin hydrogels as electrolytic media has been evaluated considering different criteria. Results indicate that κ-carrageenan-based hydrogel is the most suitable to perform as electrolyte due to the appropriate combination of properties: mechanical stability, ease of preparation, lack of water leaking, and good medium for the electrochemical response of PEDOT electrodes. Cyclic voltammetry and galvanostatic charge-discharge assays indicate that OESCs based on PEDOT electrodes and κ-carrageenan hydrogel as electrolyte exhibits a good supercapacitor response in terms of specific capacitance, cycling stability, small leakage current and low self-discharging tendency. On the basis of these good properties, four OESC devices were assembled in series and used to power a red LED, confirming that, in addition to advantageous characteristics (e.g. elimination of liquid leaking and enhancement of the device compactness), the designed biohydrogel-containing OESC exhibits potential for practical applications. On the other hand, preliminary assays have been performed loading the κ-carrageenan hydrogel with polyaniline nanofibers, which act as a redox additive. OESC devices prepared using such loaded biohydrogel have been found to be very promising and, therefore, future work is oriented towards the improvement of their design. © The Royal Society of Chemistry 2016.Authors are indebted to supports from MICINN and FEDER (MAT2012-34498), the University of Regensburg and the DFG (DI 1748/3-1). M. M. P.-M. thanks financial support through a FPI-UPC grant and a mobility DAAD Research Grant for Doctoral Candidates and Young Academics and Scientists (German Academic Exchange Service, DAAD). D. D. D. thanks the DFG for the Heisenberg Professorship Award. Support forthe research of C.A. was received through the prize ?ICREA Academia? for excellence in research funded by the Generalitat de Catalunya.Peer reviewe