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Biniak S.,Nicolaus Copernicus University | Pakula M.,Naval University of Gdynia | Swiatkowski A.,Military University of Technology | Bystrzejewski M.,University of Warsaw | Blazewicz S.,Academy of Mining and Metallurgy of Poland
Journal of Materials Research

Activated carbon Norit R3-ex (demineralized) was annealed at various temperatures (950-2700 °C) in an argon atmosphere. The changes of the porosity of the products were characterized on the basis of N2 adsorption isotherms (at 77 K). The texture of the samples was investigated by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The presence of surface oxygen (Fourier transform infrared) and its content in the surface layer (from energy dispersive spectroscopy) were determined. The electrical resistivity of powdered samples was measured. Cyclovoltammetry of carbon (powdered electrodes) were carried out and the electrical double-layer capacitances were estimated from the cyclic voltammetry curves. Heat treatment increased the degree of crystallization of the samples, which was correlated with changes in their conductivity. A rapid drop in porosity (at 1800-2100 °C) took place in parallel with a decrease in the electrical double layer capacity. The presence of surface oxygen as a result of oxygen chemisorption on freshly annealed carbon samples was confirmed using several methods. © 2010 Materials Research Society. Source

Bratek W.,Wroclaw University of Technology | Swiatkowski A.,Military University of Technology | Pakula M.,Naval University of Gdynia | Biniak S.,Nicolaus Copernicus University | And 2 more authors.
Journal of Analytical and Applied Pyrolysis

Poly(ethylene)terephthalate (PET) waste was subjected to carbonization in a nitrogen stream at 1098 K. The coke was then activated in a carbon dioxide stream under various conditions: temperatures of 1173, 1198 and 1213 K as well as process times of 4, 5, 6 and 8 h. The activated carbons were characterized using various methods: the structure from Raman and XRD measurements, the porosity from low temperature nitrogen adsorption, the surface properties from cyclic voltammetry and the hydrogen storage capacity from the low temperature adsorption isotherm of H2. The results demonstrated the importance of the temperature and the duration of the process. Higher temperatures result in the etching of graphitic domains of better crystallinity. A relatively small increase in activation time at the highest temperature used yielded a significant increase in the degree of burn-off and porous structure development. The microporosity of these carbons is similar to that of commercial activated carbons. They also have a similar capacity to adsorb water pollutants (e.g. 4-chlorophenol). The PET carbon sample with maximum burn-off exhibited higher values of the microporous structure parameters and the electric double layer capacity in electrolyte solution than the other three samples. The same sample exhibits a sufficient hydrogen storage capacity, which after optimization of the activation conditions should yield an effective storage material. This confirms the possibility of producing activated carbon from waste PET with satisfactory properties by the simple processes of carbonization and activation. The activated carbons obtained have potential use as water pollutant adsorbents, low-cost materials for hydrogen storage and electrode materials in supercapacitors or fuel cells. © 2012 Elsevier B.V. Source

Diduszko R.,Polish Tele and Radio Research Institute | Gac W.,Maria Curie Sklodowska University | Pakula M.,Naval University of Gdynia | Swiatkowski A.,Military University of Technology
Reaction Kinetics, Mechanisms and Catalysis

A commercial Pd/activated carbon catalyst (10%) was treated using several redox processes: reduction with gaseous hydrogen at 140 °C, reduction by negative electrochemical polarization in acidic and basic environments, oxidation with aqueous hydrogen peroxide, and positive electrochemical polarization in acidic and basic environments. To establish the electrochemical reduction/oxidation conditions, the potentials of hydrogen and oxygen evolution at Pd/AC powder electrodes were determined from cyclic voltammetric (CV) measurements. The samples were examined for the presence of palladium oxide phases on dispersed metal particles using XRD, TPR, and TPD. The metal oxide phase disappeared following hydrogen and electrochemical reduction. Oxidative treatment of the commercial catalyst differentiated the palladium oxide layers on the metal particle surface. Changes in the surface chemistry of the Pd/PdO/AC system were confirmed by the electrochemical behavior of electrodes prepared from the carbon samples. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source

Hofman M.,Adam Mickiewicz University | Swiatkowski A.,Military University of Technology | Pakula M.,Naval University of Gdynia | Biniak S.,Nicolaus Copernicus University
Reaction Kinetics, Mechanisms and Catalysis

Various Pd amounts (5 and 20 %wt) were chemically deposited on two different carbon materials (activated carbon and carbon black). Support materials were characterized using low-temperature N 2 adsorption and FTIR spectroscopy. SEM images and X-ray diffraction patterns were obtained for the samples tested. Cyclic voltammetric curves in 0.1 M H 2SO 4 were recorded over a variable sweep potential range for carbon materials with and without Pd. For comparison, the same electrochemical measurements were performed for powdered palladium. The hydrogen electro-oxidation potential decreased and the removal of adsorbed hydrogen by activated carbon-supported palladium was facilitated, which enables these systems to be used as anodes in hydrogen-oxygen fuel cells. © 2012 The Author(s). Source

Biniak S.,Nicolaus Copernicus University | Swiatkowski A.,Military University of Technology | Pakula M.,Naval University of Gdynia | Sankowska M.,Military University of Technology | And 2 more authors.

Several types of carbon materials (activated carbon, carbon black, multiwalled carbon nanotubes) differing in porosity and surface chemistry were used to prepare powdered electrodes. Activated carbon (Norit R3-ex) was demineralized and modified by oxidation with conc. HNO 3, heat treatment in NH 3 at 900 °C or heat treatment in argon at 1800 °C. Carbon black (Vulcan XC72) was flushed with an organic solvent, while the MWCNTs were functionalized to the hydroxyl and carboxyl forms. Nitrogen adsorption isotherms were used to characterize the pore structure of these materials. Their surface chemistry was assessed using thermogravimetry (TG), elemental analysis, FTIR, EDS and XPS. The ability to adsorb (isotherms) 4-chlorophenol (4-CP) in aqueous solution was determined. Cyclovoltammetric (CV) measurements of powdered carbon electrodes were carried out for blank electrolyte solution (0.1 M Na 2SO 4) and with different concentrations of 4-CP. Changes in the electric double layer capacity and other electrochemical parameters were estimated from the CV curves. The dependence of the electrochemical behavior of a powdered carbon bed on porosity and surface chemistry is analyzed and discussed. The electrochemical properties were related to chlorophenol adsorption ability and FTIR spectral analysis of the adsorption layer. © 2012 Published by Elsevier Ltd. Source

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