Thermally Expanded Graphite Incorporated with PEDOT:PSS Based Anode for Microbial Fuel Cells with High Bioelectricity Production

Modification of anodes with highly biocompatible materials could enhance bacterial adhesion, growth, and improve the rate of electron-transfer ability in microbial fuel cells (MFCs). As such, there has been increasing interest in the development of innovative anode materials to prepare high-performance MFCs. We report the synthesis of poly(3,4-ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) doped with thermally expanded graphite (TEG) composite coated carbon felt (CF) as anode for MFCs. For this purpose, as-synthesized PEDOT:PSS/TEG composite was characterized using high-resolution scanning electron microscopy (HR-SEM), and Raman and Fourier transform infrared (FT-IR) spectroscopies which indicated successful incorporation of TEG within PEDOT:PSS film. Furthermore, the electrochemical activity of the PEDOT:PSS/TEG coated CF was employed as the anode in the MFCs with sewage water as an anolyte. PEDOT:PSS/TEG@CF anode exhibited higher ion-transfer ability, superior bio-electrochemical conductivity, and excellent capacitance. Using the PEDOT:PSS/TEG@CF anode, we have constructed MFCs which exhibited good power (68.7 mW/m2) and current (969.3 mA/m2) densities compared to the unmodified CF based anode. The reliability of the MFCs performance was also investigated by testing three independently prepared MFCs with PEDOT:PSS/TEG@CF anodes which all showed a constant voltage (~540 mV) due to the higher stability and biocompatibility of PEDOT:PSS/TEG@CF.

CARBON NANOPARTICLES BASED ON THERMALLY EXPANDED GRAPHITE: EFFECT OF THE TEG OBTAINING ROUTE ON THE PARTICLES MORPHOLOGY

В работе представлены результаты исследования морфологии углеродных наночастиц, образующихся при жидкофазном расслоении терморасширенного графита в трет-бутаноле. Используемый в работе терморасширенный графит получен путем термического расширения соинтеркалата нитрата графита с уксусной и муравьиной кислотами в режиме термоудара при 500°С и 900 °С. Исходный соинтеркалант по данным рентгенофазового анализа представляет собой смесь соединений II-й и IV-й стадий интеркалирования. Методом просвечивающей электронной микроскопии установлено, что дисперсии углеродных наночастиц, образующиеся при расслоении терморасширенного графита в трет-бутаноле под действием ультразвука, содержат в основном малослойные графены, планарные размеры которых достигают 8 мкм. Обсуждается влияние условий получения терморасширенного графита на морфологию образующихся углеродных наночастиц. Дисперсии на основе терморасширенного графита, полученного при более низкой температуре, помимо малослойных графенов содержат также значительное количество аморфных углеродных частиц с планарными размерами до 100 нм. The paper presents the investigation results of the morphology of carbon nanoparticles formed during liquid-phase exfoliation of thermally expanded graphite in tert-butanol. The thermally expanded graphite used in this work was obtained by thermal expansion of graphite nitrate with acetic and formic acids in the thermal shock mode at 500 °C and 900 °C. Initial cointercalate was shown by powder X-ray diffraction analysis to be the mixture of the II and the IV stage intercalation compounds. It has been established by transmission electron microscopy that dispersions of carbon nanoparticles formed during the exfoliation of thermally expanded graphite in tert-butanol via sonication contain mainly few-layer graphenes, the planar dimensions of which reach 8 pm. The influence of the conditions for thermally expanded graphite obtaining on the morphology of resulting carbon nanoparticles is discussed. Dispersions based on thermally expanded graphite obtained at a lower temperature, in addition to few-layer graphenes, also contain a significant amount of amorphous carbon particles with planar sizes up to 100 nm.

Polyamide self-lubricating composites filled with thermolysis products of lignin: composition, structure, properties

Compositions of antifriction composites with a polyamide matrix filled with carbon additives obtained by modifying hydrolytic lignin (graphite from lignin, graphite bisulfate from lignin, thermally expanded graphite from lignin) have been developed. Powders of carbon materials were impregnated with cylinder oil before being added to the polyamide matrix. The tribotechnical characteristics of filled polyamide composites, their microstructure and water absorption kinetics have been investigated. It was found that the lowest values of the friction factor are observed in composites filled with thermally expanded graphite from lignin. The friction factor for such composites is 1.5-2 times less than the indicators obtained for currently used graphites. Thus, at specific loads of 0.67 and 2.33 MPa, the friction factor was 0.065 and 0.064, respectively. The investigated antifriction composites have low water absorption compared to pure polyamide. The maximum water absorption (2.2%) in the series of the studied composites had the samples filled with graphite from lignin with an oil content of 9%. According to the data of microstructural analysis, the structure of composites with additives of carbon materials from lignin is homogeneous. The components, including the oil plasticizer, are evenly distributed, the bulk of the oil is localized in the interlayer spaces. The elemental composition of the composites indicates the high chemical purity of the composites. Antifriction composites with the proposed additives are recommended for use in friction units operating in an aqueous mediumor an environment with high humidity.

Triple graphite nitrate cointercalation compounds with acetic acid as precursors for thermally expanded graphite and carbon nanoparticles

Triple graphite nitrate cointercalation compounds (GNCCs) with acetic acid were synthesized, characterized by powder XRD and SEM methods, and used as a source of the thermally expanded graphite (TEG). Structural reorganization of graphite nitrate-acetate and triple GNCCs with acetic acid as a result of their exposition in air is discussed on the base of powder XRD data. Dispersions of carbon nanoparticles were prepared by liquid phase exfoliation of TEGs obtained from the GNCCs. It was demonstrated by TEM method that using of the studied TEGs as a source of carbon nanoparticles favours formation of few-layered graphene.

Carbon nanomaterials for supercapacitors: two electrode scheme

In this paper, the electrochemical and texture characteristics of electrode materials made of a number of promising carbon materials for supercapacitors were considered. Carbon nanofibers, thermally expanded graphite, and activated carbon derived from rice hulls were used as electrodes for supercapacitors. The paper presents a technique of synthesis of these electrode materials. A comparison of the capacitive characteristics of the electrodes using two-electrode scheme was carried out.