Catia Arbizzani

Conducting polymers as electrode materials in supercapacitors

Abstract This paper summarizes the performance data of conventional and especially designed thiophene-based conducting polymers for use as positive and negative electrodes in n/p type supercapacitors. Performance data of polymer composite electrodes are also compared with those of high surface area carbon-based composite electrodes. On the basis of capacity, capacitance and electrode charging resistance data, we selected the best electrode materials, and assembled and tested galvanostatic charge–discharge cycles n/p type pMeT-based supercapacitors and hybrid supercapacitors with pMeT as positive electrode active material and activated carbon as negative. The results of this investigation demonstrate that a conventional polymer such as pMeT can be successfully used in the supercapacitor technology when a hybrid configuration is realized; its use is, indeed, a great advantage because the hybrid supercapacitor outperforms the double-layer carbon supercapacitors presently on the market in terms of specific energy and power.

New trends in electrochemical supercapacitors

The present paper compares the performance of an n/p-type polymer supercapacitor based on n- and p-doped poly(3-methylthiophene) (pMeT) and of a hybrid supercapacitor, based on p-doped pMeT as positive electrode and activated carbon as negative, with that of a double-layer activated carbon supercapacitor (DLCSs), which is representative of the current state of supercapacitor technology. The data on the n/p-type supercapacitor demonstrate that this device is not fully competitive with the DLCSs because of its lower discharge capacity, although all the charge is delivered at high potentials and this makes it suitable for high-voltage applications. The data on the hybrid supercapacitor demonstrate that this device outperforms DLCSs, delivering higher average and maximum specific powers and significantly higher specific energy in the potential region above 1.0 V.

Polymer-based supercapacitors

The use of electronically conducting polymers (ECPs) as pseudocapacitive electrode materials in high-power supercapacitors is a challenge to overcome the performance of carbon-based double-layer supercapacitors for applications requiring high power levels. ECPs provide different supercapacitor configurations but devices with the polymer n-doped form as the negative electrode and the p-doped form as the positive one are the most promising in term of energy and power. This type of supercapacitor has indeed a high operating voltage, it is able to deliver all the doping charge and it has in the charged state both electrodes in the conducting (p- and n-doped) states. Data for poly(3-methylthiophene) positive and negative electrodes, envisioned for a n/p-type supercapacitor, as well as data for cyclability of supercapacitors with composite electrodes based on such conventional polymer are here reported and discussed. The capacitance and cycling stability of poly(3-methylthiophene) are sufficiently high to take this polymer into consideration for supercapacitor technology.

Microbial fuel cells: From fundamentals to applications. A review

In the past 10–15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

Polymer Selection and Cell Design for Electric‐Vehicle Supercapacitors

Supercapacitors are devices for applications requiring high operating power levels, such as secondary power sources in electric vehicles (EVs) to provide peak power for acceleration and hill climbing. While electronically conducting polymers yield different redox supercapacitor configurations, devices with the n-doped polymer as the negative electrode and the p-doped polymer as the positive one are the most promising for EV applications. Indeed, this type of supercapacitor has a high operating potential, is able to deliver all the doping charge and, when charged, has both electrodes in the conducting (p- and n-doped) states. This study reports selection criteria for polymer materials and cell design for high performance EV supercapacitors and experimental results of selected polymer materials.

N- and P-doped polydithieno[3,4-B:3',4'-D] thiophene : a narrow band gap polymer for redox supercapacitors

Abstract We studied polydithieno[3,4-b:3′,4′-d]thiophene (pDTT), an electronically conducting polymer with a narrow band gap, and our data clearly demonstrated that the charge injection of both signs is possible in electrolytic media with tetraalkylammonium salts. This is an important feature for the development of polymer-based redox supercapacitors with high charge storage capacity and high operating potential. Electrochemical characterization data of p- and n-doped pDTT films electrosynthesized in different conditions and on several electrode materials are reported. Successful results were achieved on carbon paper electrodes where the same p- and n-doping levels were reached.

Preparation and electrochemical characterization of a polymer Li1.03Mn1.97O4/pEDOT composite electrode

Abstract The development and characterization of a polymeric composite based on non-stoichiometric Li 1.03 Mn 1.97 O 4 spinel operating at 4 V and poly(3,4-ethylenedioxy)thiophene (pEDOT) are reported. In this composite the pEDOT substitutes the carbon usually mixed with the inorganic oxide-based electrodes to improve their electronic conductivity; the pEDOT thus functions as an electronic conductor and is electroactive in the same potential range of LiMn 2 O 4 . Electrochemical data for pure pEDOT and for composites of pEDOT/carbon, conventional Li 1.03 Mn 1.97 O 4 /carbon and polymer Li 1.03 Mn 1.97 O 4 /pEDOT are reported and discussed.

Polymer-based electrochromic devices—I. Poly(3-methylthiophenes)

Abstract The basic aspects of electrochromism induced by a p-doping/undoping process of conjugated polymers are briefly described. The most important requisites for an electrochromic device are discussed, and polymer electrochromic performance data as well as the test results of a polymer-based variable light transmission electrochromic device are reported. The colour contrast control of conjugated polymers by “tailoring” their conjugation length is discussed and spectroelectrochemical data of poly(3-methylthiophenes) electrosynthesized from 3-methylthiophene isomeric dimers and isomeric tetramers are reported.

Characterization by impedance spectroscopy of a polymer-based supercapacitor

Abstract The performance of a polymer redox supercapacitor based on poly(dithieno[3,4-b: 3′,4′-d] thiophene) in liquid and in polymer gel electrolyte was tested for capacity, energy density, power density and self-discharge. The results are very promising and demonstrate the viability of a symmetric supercapacitor based on an n -and p -doped electronically conducting polymer.

Self-powered supercapacitive microbial fuel cell: The ultimate way of boosting and harvesting power

In this work, for the first time, we demonstrate a supercapacitive microbial fuel cell which integrates the energy harvesting function of a microbial fuel cell (MFC) with the high-power operation of an internal supercapacitor. The pursued strategies are: (i) the increase of the cell voltage by the use of high potential cathodes like bilirubin oxidase (BOx) or iron-aminoantipyrine (Fe-AAPyr); (ii) the use of an additional capacitive electrode (additional electrode, AdE) which is short-circuited with the MFC cathode and coupled with the MFC anode (MFC-AdE). The high working potential of BOx cathode and the low impedances of the additional capacitive electrode and the MFC anode permitted to achieve up to 19 mW (84.4 Wm(-2), 152 Wm(-3)), the highest power value ever reported for MFCs. Exploiting the supercapacitive properties of the MFC electrodes allows the system to be simpler, cheaper and more efficient without additional electronics management added with respect to an MFC/external supercapacitor coupling. The use of the AdE makes it possible to decouple energy and power and to achieve recharge times in the order of few seconds making the system appealing for practical applications.