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Węgle aktywne jako materiał elektrodowy dla kondensatorów elektrochemicznych

Nowicki P., Wachowska H.

Wiadomości Chemiczne

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2009

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[Z] 63, 5-6

461-476

EN

Electrochemical capacitors (also known as supercapacitors, ultracapacitors or electric double-layer capacitors) have been extensively investigated at a number of research centres in the world. The main reason of this interest is the possibility of their use as an alternative or complement to other electric energy storage or generation devices, e.g. batteries or fuel cells as well as their potential applications in many fields including surge-power delivery devices for electric vehicles, backup-power storage for calculators, starting power for fuel cells, etc. [1]. Research concerning electrochemical capacitors is presently divided into two main areas: (a) the redox supercapacitors (also called pseudocapacitors) and (b) the electrochemical double layer capacitors (EDLC) [2]. Development of electrochemical capacitors is connected with a search of optimal electrode materials able to a high, efficient accumulating of electrical energy, high dynamic of charge exchange with a simultaneous long durability [3]. The most widely used materials for electrochemical capacitors are active carbons. This is due to their unique physico-chemical properties such as: high electrical and thermal conductivity, low density, high corrosion resistance, well developed surface area, controlled porosity as well as availability and relatively low cost [2, 4]. This paper presents the review of literature on the influence of the physico-chemical properties of active carbons on their capacitance parameters. Much attention has been paid to the redox supercapacitors.

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Modyfikowane węgle aktywne : otrzymywanie oraz perspektywiczne kierunki ich wykorzystania

Nowicki P., Wachowska H.

Wiadomości Chemiczne

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2008

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[Z] 62, 11-12

999-1016

EN

The attractive properties of active carbons are determined by the well-developed surface area and the type, number and mode of bonding of different heteroatoms (oxygen, sulphur, nitrogen, boron, phosphorus, chlorine) with the carbon surface [3-16]. Recently, much attention has been devoted to oxygen and/or nitrogen-enriched active carbons because of a wide gamut of their applications: for adsorption of compounds of acidic character such as SO2, H2S, NOx, CO2 from the gas phase [77-90] or for adsorption of metal ions [96-100]. Modified active carbons are also very effective in removal of many organic compounds, such as aromatic and aliphatic amines or phenol and its derivatives [101-107]. Of particular importance is the application of these carbons for production of electrodes in electrochemical capacitors in order to increase their capacity [21, 61, 117-121]. This article presents a survey of literature devoted to methods of synthesis and application of modified active carbons. A special emphasis was placed on the method of preparation nitrogen-enriched active carbons.

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Badanie fizykochemicznych właściwości chemicznie modyfikowanych węgli aktywnych

Repelewicz M., Choma J.

Inżynieria i Ochrona Środowiska

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2005

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T. 8, nr 1

5-17

PL

Badano fizykochemiczne właściwości węgli aktywnych otrzymanych przez modyfikację węgla handlowego poprzez osadzanie depozytu węglowego z rozkładu chlorku metylenu. Na podstawie niskotemperaturowej adsorpcji azotu wyznaczono podstawowe parametry struktury porowatej. Stosując metodę Boehma, wyznaczono stężenie powierzchniowych grup funkcyjnych zawierających tlen. Metodą inwersyjnej chromatografii gazowej (IGC) wyznaczono izotermy adsorpcji alkoholi alifatycznych od C=1 do C=4 oraz benzenu i chloroformu. Na podstawie otrzymanych izoterm adsorpcji obliczono wartości izosterycznego ciepła adsorpcji qst. Stwierdzono istotny wpływ depozytu węglowego na właściwości strukturalne i powierzchniowe węgla aktywnego.

EN

Physicochemical properties of activated carbons prepared by chemical modification of a commercial active carbon were studied. The modification consisted in forming so-called carbon deposit from methylene chloride pyrolysis. The obtained modified activated carbons contained carbon deposit within the range of 7.28 to 20.91% by weight. The basic parameters of porous structure were calculated by means of low-temperature nitrogen adsorption. The specific surface, determined by BET method within the range of relative pressures (p/p0 0.01 to 0.2, is going down regularly from 790 m2/g (the commercial carbon) to 360 m2/g (the carbon containing 20.91% by weight carbon deposit). Moreover, the micropore volume (calculated by means Barrett, Joyner and Halenda method) changes also regularly from 0.34 to 0.15 cm3/g, similarly as total pore volume from 0.40 to 0.19 cm3/g. The results point out that, forming a carbon deposit has a great influence on the pore structure of the carbon materials, and during the modification adsorptive properties to nitrogen are getting worse markedly. Using the Boehm method the concentration of surface acidic functional groups containing oxygen such as: carboxylic, lactic, carbonyl and phenyl groups, were determined. The total concentration of surface functional groups is almost the same for the studied carbons except carbon possessing 20.91% by weight carbon deposit (here the concentration is smaller). On the other hand, the carbons differ in the concentration of individual groups. This effect is most visible in the concentration of carboxylic groups: the commercial carbon contains 0.016 mmol/g carboxylic groups and the all modified carbons contain about 0.55 mmol/g of these groups. Adsorption isotherms of aliphatic alcohols (C=1 to C=4), benzene and trichloromethane on all studied carbons were determined by means of inverse gas chromatography (IGC). The measurements were carried out by a Mera-Elmet type N-504 chromatograph, using a thermoconductometic detector (TCD), helium as a carrier gas, within the temperature range from 333 to 493 K. The adsorption isotherms were calculated by the peak profile method by graphic integration of an individual chromatogram. The measurements of adsorption isotherms at various temperatures permit to calculate isosteric adsorption heat (qst). It can be said generally that the isosteric adsorption heat is going up with the degree of surface covering. If the degree of surface covering is small, the magnitude of heat effect depends mainly on interaction between adsorbate-adsorbent. Whereas for the increasing degree of surface covering there can be additional adsorbate--adsorbate interaction. Additionally, the molecules of aliphatic alcohols can create hydrogen bonds with the carbon surface having adequate surface functional groups. The obtained values of isosteric adsorption heats are about 60 kJ/mol to the extent of degree of surface covering to 30 μmol/g. It can suggest that the dominant adsorption mechanism is physical adsorption.