Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel

3D‐Poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes are prepared using the multi‐step template‐assisted approach. Specifically, poly(lactic acid) nano‐ and microfibers collected on a previously polymerized PEDOT film are used as templates for PEDOT nano‐ and microtubes, respectively. Morphological analysis of the samples indicates that 3D‐PEDOT electrodes obtained using a low density of templates, in which nano‐ and microtubes are clearly identified, exhibit higher porosity, and specific surface than conventional 2D‐PEDOT electrodes. However, a pronounced leveling effect is observed when the density of templates is high. Thus, electrodes with microtubes still present a 3D‐morphology but much less marked than those prepared using a low density of PLA microfibers, whereas the morphology of those with nanotubes is practically identical to that of films. Electrochemical studies prove that solid supercapacitors prepared using 3D‐PEDOT electrodes and κ‐carrageenan biohydrogel as electrolytic medium, exhibit higher ability to exchange charge reversibly and to storage charge than the analogues prepared with 2D‐electrodes. Furthermore, solid devices prepared using 3D‐electrodes and κ‐carrageenan biohydrogel exhibit very similar specific capacitances that those obtained using the same electrodes and a liquid electrolyte (i.e., acetonitrile solution with 0.1 M LiClO₄). These results prove that the success of 3D‐PEDOT electrodes is independent of the electrolytic medium.

     

A Contribution to the Mechanism of Formation of Humic Acids in Coal

This paper presents a study of the influence of mechanochemical activation of coal on the process of formation and degradation of humic acids. The increasing period of mechanical activation of coal causes an increase in hydrophility, electrophoretic mobility, and of electrokinetic potential of surface layers as a result of acidic carboxyl and phenolic OH groups. The effective activation requires a short period of grinding. The increased time of activation causes the secondary processes of grain agglomeration and degradation of humic acids.     

Reactivity of Coal Activated by Mechanochemical Treatment

The paper presents new information on the transformation changes in the chemical structure of coal caused by mechanical activation using the GACL procedure. In the case of chemical treatment of Pittsburgh bituminous coal, the CAPTO method has confirmed a temperature T _max shift for identification of carbonaceous and sulfur compounds (T _max/S_organic) – 50°C; T _max/C_organic – 50°C). The temperature reduction of the thermal destruction maximum of carbonaceous and sulfur aromatic compounds is a result of activation of the coal structure of bituminous coals. The environmental effect of desulfurization (approx. 70%), detoxication, e.g., removal of arsenic (approx. 95%) and increase in the content of humic acids in the treated coal batch, have been proved by mechanical activation of Nováky brown coal using the GACL procedure. It is possible to improve the technological parameters of chemical treatment by optimization of the GACL procedure.     

Course of degradation and build‐up reactions in isotactic polypropylene during peroxide decomposition

In the investigation of the course of degradation and build‐up reactions during the decomposition of the tert‐butyl perbenzoate (TBPB) (at eight different concentrations) in isotactic polypropylene (iPP), it was found that, at the beginning of the peroxide decomposition at all investigated peroxide concentrations from 4.62–200 mmol/kg iPP, the degradation reactions of iPP prevailed. At the TBPB concentration of ≤37.0 mmol/kg iPP during the whole period of peroxide decomposition, degradation reactions leading to a lower of molecular mass of PP prevailed. But at higher peroxide concentrations of TBPB ≥74.4 mmol/kg iPP and at the later stage of peroxide decomposition, a predominance of the build‐up reactions, that is, an increase the molecular mass, was observed. The degradation and build‐up reactions were determined from the measurements of the melting‐flow indexes of the peroxide‐treated iPP samples. The reaction mechanism of the degradation and build‐up reactions in iPP is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 886–893, 2000