The mass implementation of renewable energies is limited by the absence of efficient and affordable technology to store electrical energy. Thus, the development of new materials is needed to improve the performance of actual devices such as batteries or supercapacitors. Herein, the facile consecutive chemically oxidative polymerization of poly(1-amino-5-chloroanthraquinone) (PACA) and poly(3,4-ethylenedioxythiophene (PEDOT) resulting in a water dispersible material PACA-PEDOT is shown. The water-based slurry made of PACA-PEDOT nanoparticles can be processed as film coated in ambient atmosphere, a critical feature for scaling up the electrode manufacturing. The novel redox polymer electrode is a nanocomposite that withstands rapid charging (16 A g−1) and delivers high power (5000 W kg−1). At lower current density its storage capacity is high (198 mAh g−1) and displays improved cycling stability (60% after 5000 cycles). Its great electrochemical performance results from the combination of the redox reversibility of the quinone groups in PACA that allows a high amount of charge storage via Faradaic reactions and the high electronic conductivity of PEDOT to access to the redox-active sites. These promising results demonstrate the potential of PACA-PEDOT to make easily organic electrodes from a water-coating process, without toxic metals, and operating in non-flammable aqueous electrolyte for large scale pseudocapacitors. 

Powering the future, while maintaining a cleaner environment and a strong socioeconomic growth, is going to be one of the biggest challenges faced by mankind in the 21st century. The first step in overcoming the challenge for a sustainable future is to use energy more efficiently so that the demand for fossil fuels can be reduced drastically. The second step is a transition from the use of fossil fuels to renewable energy sources. In this sense, organic electrode materials are becoming increasingly attractive compared to inorganic electrode materials which have reached a plateau regarding performance and have severe drawbacks in terms of cost, safety and environmental friendliness. Using organic composites based on conducting polymers, such as polypyrrole, and abundant, cheap and naturally occurring biopolymers rich in quinones, such as lignin, has recently emerged as an interesting alternative. These materials, which exhibit electronic and ionic conductivity, provide challenging opportunities in the development of new charge storage materials. This review presents an overview of recent developments in organic biopolymer composite electrodes as renewable electroactive materials towards sustainable, cheap and scalable energy storage devices.

Developing sustainable organic electrode materials for energy storage applications is an urgent task. We present a promising candidate based on the use of lignin, the second most abundant biopolymer in nature. This polymer is combined with a conducting polymer, where lignin as a polyanion can behave both as a dopant and surfactant. The synthesis of PEDOT/Lig biocomposites by both oxidative chemical and electrochemical polymerization of EDOT in the presence of lignin sulfonate is presented. The characterization of PEDOT/Lig was performed by UV-Vis-NIR spectroscopy, FTIR infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, cyclic voltammetry and galvanostatic charge-discharge. PEDOT doped with lignin doubles the specific capacitance (170.4 F g(-1)) compared to reference PEDOT electrodes (80.4 F g(-1)). The enhanced energy storage performance is a consequence of the additional pseudocapacitance generated by the quinone moieties in lignin, which give rise to faradaic reactions. Furthermore PEDOT/Lig is a highly stable biocomposite, retaining about 83% of its electroactivity after 1000 charge/discharge cycles. These results illustrate that the redox doping strategy is a facile and straightforward approach to improve the electroactive performance of PEDOT.

Two self-doped conjugated polyelectrolytes, having semiconducting and metallic behaviors, respectively, have been blended from aqueous solutions in order to produce materials with enhanced optical and electrical properties. The intimate blend of two anionic conjugated polyelectrolytes combine the electrical and optical properties of these, and can be tuned by blend stoichiometry. In situ conductance measurements have been done during doping of the blends, while UV vis and EPR spectroelectrochemistry allowed the study of the nature of the involved redox species. We have constructed an accumulation/depletion mode organic electrochemical transistor whose characteristics can be tuned by balancing the stoichiometry of the active material.

We report spectroelectrochemical studies to investigate the charge storage mechanism of composite polypyrrole/lignin electrodes. Renewable bioorganic electrode materials were produced by electropolymerization of pyrrole in the presence of a water-soluble lignin derivative acting as a dopant. The resulting composite exhibited enhanced charge storage abilities due to a lignin-based faradaic process, which was expressed after repeated electrochemical redox of the material. The in situ FTIR spectroelectrochemistry results show the formation of quinone groups, and reversible oxidation-reduction of these groups during charge-discharge experiments in the electrode materials. The most significant IR bands include carbonyl absorption near 1705 cm(-1), which is attributed to the creation of quinone moieties during oxidation, and absorption at 1045 cm(-1) which is due to hydroquinone moieties.

We report that hydrophobically modified amyloid fibrils form macroscopic films at the air-water interface. The hydrophobically modified fibrils are prepared in a two step process. First bovine insulin is ground with a hydrophobic compound. The resulting material is dissolved in acidic water and heated to induce assembly into fibrils incorporating the hydrophobic compounds. Upon dilution followed by asymmetric heating, resulting in convection flow, the fibrills form highly ordered films with thicknesses from 80 nm and up. The thickness of the film can be controlled by the fibril concentration and/or reaction time. The films contain anisotropic domains spanning several square centimeters. In addition, the films contains ordered assemblies of dyes that display emission of polarized light.

We show here the preparation and characterization of micrometer sized conductive helices. We utilize protein fibrils as structural templates to create chiral helices with either right or left handed helicity. The helices are coated with the conductive polymer alkoxysulfonate poly(ethylenedioxythiophene) (PEDOT-S) to create micrometer sized conductive helices. The coating acts as a stabilizer for the template structure, facilitates the preparation of solid state films and shows significant conductivity. The helices have been investigated using Circular Dichroism (CD) and scanning electron microscopy (SEM) and the conductivity have been measured for solid state films.