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Surface morphology induced electrical conductivity and specific surface area of a material play a significant role to facilitate electrochemical behavior for supercapacitor application. Therefore, the synthesis step for controlling such parameters becomes very imperative and challenging. Herein, a ZnS nanoweb is deposited directly onto Ni foam with a pre-deposited thin layer of hydrothermally prepared graphene oxide. The structure and surface morphology of the deposited ZnS is observed using XRD and SEM, respectively. The electrical conductivity of the graphene oxide supported ZnS nanoweb, determined using the four probes method, is 100.15 Scm(-1). The specific surface area is 104.42 m(2)g(-1) as determined by BET measurements. Pseudocapacitive behavior is monitored by cyclic voltammetry, and the excellent specific capacity of 3052 Fg(-1) has been found at a scan rate of 2 mVs(-1), while it is 2400.30 Fg(-1) according the galvanostatic charge-discharge profile at a current density of 3 mAcm(-2). Both values are significantly higher than those measured for bare GO or ZnS layers. The energy and power densities of GO supported ZnS nanoweb are determined in a three electrode setup, are 120 WhKg(-1) at 3 mAcm(-2) and 4407.73 Wkg(-1), respectively. In a symmetric two electrode setup, an energy density of 20.29 WhKg(-1) at 2 mAcm(-2) is observed. Hence, both symmetric and asymmetric measurements suggest that GO supported ZnS nanoweb can be applied as a suitable electrode for supercapacitors.

Paper-based conductive electrode materials of polypyrrole (PPy) and nanocellulose (NC) have received much attention lately for applications in non-metal-based energy storage devices, ion exchange, etc. The aim of this study was to study how the primary characteristics of NC raw materials impact and electrochemical properties of conductive NC-PPy composite sheets. Three NC raw materials were used: Cladophora cellulose (NCUU) produced at Uppsala University, Cladophora cellulose (NCFMC) produced at FMC Biopolymer, and microfibrillated cellulose (NCINN) produced at Innventia AB. Composite paper sheets of PPy coated on the substrate NC material were produced. The NC raw materials and the composites were characterized with a battery of techniques to derive their degree of crystallinity, degree of polymerization, specific surface area, pore size distribution, porosity, electron conductivity, charge capacity and tensile properties. It was found that the pore size distribution and overall porosity increase upon coating of NC fibres for all the samples. The charge capacity of the composites was found to decrease with the porosity of the samples. It was further found that the mechanical strength of the pristine NC sheets was largely dependent on the overall porosity, with NCINN having the highest mechanical strength and lowest porosity in the series. The mechanical properties of the composite NC-PPy sheets were significantly diminished as compared with pristine NC sheets because of the impaired H-bonding between fibres and PPy-coated nanofibres. It was concluded that to improve the mechanical properties of PPy-NC sheets, a fraction of additive bare NC fibres is beneficial. Future study may include the effect of both soluble and insoluble additives to improve the mechanical strength of PPy-NC sheets.

Composites of polypyrrole (PPy) and Cladophora nanocellulose, reinforced with 8 mu m-thick chopped carbon filaments, can be used as electrode materials to obtain paper-based energy-storage devices with unprecedented performance at high charge and discharge rates. Charge capacities of more than 200 C g-1 (PPy) are obtained for paper-based electrodes at potential scan rates as high as 500 mV s-1, whereas cell capacitances of 6070 F g-1 (PPy) are reached for symmetric supercapacitor cells with capacitances up to 3.0 F (i.e.,0.48 F cm-2) when charged to 0.6 V using current densities as high as 31 A g-1 based on the PPy weight (i.e., 99 mA cm-2). Energy and power densities of 1.75 Wh kg-1 and 2.7 kW kg-1, respectively, are obtained when normalized with respect to twice the PPy weight of the smaller electrode. No loss in cell capacitance is seen during charging/discharging at 7.7 A g-1 (PPy) over 1500 cycles. It is proposed that the nonelectroactive carbon filaments decrease the contact resistances and the resistance of the reduced PPy composite. The present straightforward approach represents significant progress in the development of low-cost and environmentally friendly paper-based energy-storage devices for high-power applications.

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg(-1), were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30-50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m(2) g(-1)) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)(6), (dT)(20), and (dT)(40) DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules.

It is demonstrated that it is possible to coat the individual fibers of wood-based nanocellulose with polypyrrole using in situ chemical polymerization to obtain an electrically conducting continuous high-surface-area composite. The experimental results indicate that the high surface area of the water dispersed material, to a large extent, is maintained upon normal drying without the use of any solvent exchange. Thus, the employed chemical polymerization of polypyrrole on the microfibrillated cellulose (MFC) nanofibers in the hydrogel gives rise to a composite, the structure of which—unlike that of uncoated MFC paper—does not collapse upon drying. The dry composite has a surface area of 90 m2/g and a conductivity of 1.5 S/cm, is electrochemically active, and exhibits an ion-exchange capacity for chloride ions of 289 C/g corresponding to a specific capacity of 80 mAh/g. The straightforwardness of the fabrication of the present nanocellulose composites should significantly facilitate industrial manufacturing of highly porous, electroactive conductive paper materials for applications including ion-exchange and paper-based energy storage devices.

This work investigates the movement of anions during potentiostatic controlled reduction of novel compositematerials consisting of high surface area cellulose substrates, extracted from the Cladophora sp. algae, coatedwith thin (∼50 nm) layers of the intrinsically conducting polymer (ICP) polypyrrole. The coating was achievedby chemical polymerization of pyrrole on the cellulose fibers with iron(III) chloride and phosphomolybdicacid, respectively. The composites are in the form of paper sheets and can be directly immersed into anelectrolyte solution for ion absorption/desorption. The motion of glutamate and aspartate anions during cathodicpolarization was investigated as a function of preceding anodic polarization at various potentials. The compositewas found to exhibit memory effect as the response to a cathodic polarization of constant magnitude produceddifferent responses depending on the magnitude of the preceding anodic potential. After the application of acathodic potential to the composite, the reduction current curvessgenerated by anions leaving thecompositeswere found to initially increase in magnitude followed by a monotonic decay. A similar responsehas not been described and analyzed for electrochemical reduction of anion containing ICP materials earlier.A theoretical model was developed to aid the analysis of the experimental data. The model accounts for bothfreely mobile anions and anions that may be temporarily trapped in a contracting PPy network during cathodicpolarization. By fitting the recorded reduction current curves to this model, detailed information about theionic movement in the composite could be obtained, which may be used to further optimize the materialsproperties of conducting polymer systems aimed for specific electrochemical ion exchange processes.

Conducting polymers for battery applications have been subject to numerous investigations during the last two decades. However, the functional charging rates and the cycling stabilities have so far been found to be insufficient for practical applications. These shortcomings can, at least partially, be explained by the fact that thick layers of the conducting polymers have been used to obtain sufficient capacities of the batteries. In the present letter, we introduce a novel nanostructured high-surface area electrode material for energy storage applications composed of cellulose fibers of algal origin individually coated with a 50 nm thin layer of polypyrrole. Our results show the hitherto highest reported charge capacities and charging rates for an all polymer paper-based battery. The composite conductive paper material is shown to have a specific surface area of 80 m(2) g(-1) and batteries based on this material can be charged with currents as high as 600 mA cm(-2) with only 6% loss in capacity over 100 subsequent charge and discharge cycles. The aqueous-based batteries, which are entirely based on cellulose and polypyrrole and exhibit charge capacities between 25 and 33 mAh g(-1) or 38-50 mAh g(-1) per weight of the active material, open up new possibilities for the production of environmentally friendly, cost efficient, up-scalable and lightweight energy storage systems.