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Chuan Lin

Bio: Chuan Lin is an academic researcher from University of South Carolina. The author has contributed to research in topics: Pseudocapacitance & Carbonization. The author has an hindex of 10, co-authored 14 publications receiving 1390 citations.

Papers
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Journal ArticleDOI
TL;DR: Very fine cobalt oxide xerogel powders were prepared using a unique solution chemistry associated with the sol-gel process as mentioned in this paper, and the effect of thermal treatment on the surrace area, pore volume, crystallinity, particle structure, and corresponding electrochemical properties was investigated and found to have significant effects on all of these properties.
Abstract: Very fine cobalt oxide xerogel powders were prepared using a unique solution chemistry associated with the sol-gel process The effect of thermal treatment on the surrace area, pore volume, crystallinity, particle structure, and corresponding electrochemical properties of the resulting xerogels was investigated and found to have significant effects on all of these properties The xerogel remained amorphous as Co(OH) 2 up to 160°C, and exhibited maxima in both the surface area and pore volume at this temperature With an increase in the temperature above 200°C, both the surface area and pore volume decreased sharply, because the amorphous Co(OH) 2 decomposed to form CoO that was subsequently oxidized to form crystalline Co 3 O 4 In addition, the changes in the surface area, pore volume, crystallinity, and particle structure all had significant but coupled effects on the electrochemical properties of the xerogels A maximum capacitance of 291 F/g was obtained for an electrode prepared with the CoO x xerogel calcined at 150°C, which was consistent with the maxima exhibited in both the surface area and pore volume; this capacitance was attributed solely to a surface redox mechanism The cycle life of this electrode was also very stable for many thousands of cycles

441 citations

Journal ArticleDOI
01 Jan 1997-Carbon
TL;DR: In this article, mesoporous carbon xerogels were prepared from the sol-gel polymerization of resorcinol with formaldehyde (RF) followed by carbonization.

346 citations

Journal ArticleDOI
TL;DR: In this article, nine different solgel derived carbon xerogels were prepared with different pore structures by varying the carbonization temperature (in flowing ) and activation time (in in ).
Abstract: Nine different sol‐gel derived carbon xerogels were prepared with different pore structures by varying the carbonization temperature (in flowing ) and activation time (in in ). For each of these carbon xerogels, mesopore and micropore size distributions and cumulative surface areas were extracted from a density functional theory analysis. Increasing the carbonization temperature caused a decrease in the number of micropores in the 6 A range but had little effect on the mesopore size distribution and thus mesopore cumulative surface area. Increasing the activation time caused an increase in the number of both micro‐ and mesopores where pores in the 6 A width range eventually became pores in the 12 A width range. The electrochemical double‐layer capacitance (DLC) of the carbon xerogels was found to correlate well with changes in the pore structure, and it was determined that pores less than about 8 A in width did not contribute to the DLC. © 1999 The Electrochemical Society. All rights reserved.

177 citations

Journal ArticleDOI
01 Jan 2000-Carbon
TL;DR: In this article, the effects of carbonization temperature and CO2-activation time on the pore structure of carbon xerogels, derived from the sol-gel polymerization of resorcinol-formaldehyde resins, were studied in detail.

132 citations

Journal ArticleDOI
TL;DR: In this paper, a carbon-ruthenium xerogel containing 14 wt% Ru was used to obtain a specific capacitance of 256 F/g (single electrode), which corresponded to more than 50% utilization of Ru.
Abstract: There has been increasing interest in electrochemical capacitors as energy storage systems because of their high power density and long cycle life, compared to battery devices. According to the mechanism of energy storage, there are two types of electrochemical capacitors. One type is based on double layer (dl) formation due to charge separation, and the other type is based on a faradaic process due to redox reactions. Sol-gel derived high surface area carbon-ruthenium xerogels were prepared from carbonized resorcinol-formaldehyde resins containing an electrochemically active form of ruthenium oxide. The electrochemical capacitance of these materials increased with an increase in the ruthenium content indicating the presence of pseudocapacitance associated with the ruthenium oxide undergoing reversible faradaic redox reactions. A specific capacitance of 256 F/g (single electrode) was obtained from a carbon xerogel containing 14 wt% Ru, which corresponded to more than 50% utilization of the ruthenium. The double layer accounted for 40% of this capacitance. This material was also electrochemically stable, showing no change in a cyclic voltammogram for over 2,000 cycles.

125 citations


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TL;DR: This work has shown that combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries.
Abstract: Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

14,213 citations

Journal ArticleDOI
TL;DR: Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density.
Abstract: In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

7,642 citations

Journal ArticleDOI
TL;DR: Supercapacitors are able to store and deliver energy at relatively high rates (beyond those accessible with batteries) because the mechanism of energy storage is simple charge-separation (as in conventional capacitors) as discussed by the authors.

3,620 citations

Journal ArticleDOI
TL;DR: The charge storage mechanism in MnO2 electrode, used in aqueous electrolyte, was investigated by cyclic voltammetry and X-ray photoelectron spectroscopy as discussed by the authors.
Abstract: The charge storage mechanism in MnO2 electrode, used in aqueous electrolyte, was investigated by cyclic voltammetry and X-ray photoelectron spectroscopy. Thin MnO2 films deposited on a platinum substrate and thick MnO2 composite electrodes were used. First, the cyclic voltammetry data established that only a thin layer of MnO2 is involved in the redox process and electrochemically active. Second, the X-ray photoelectron spectroscopy data revealed that the manganese oxidation state was varying from III to IV for the reduced and oxidized forms of thin film electrodes, respectively, during the charge/discharge process. The X-ray photoelectron spectroscopy data also show that Na+ cations from the electrolyte were involved in the charge storage process of MnO2 thin film electrodes. However, the Na/Mn ratio for the reduced electrode was much lower than what was anticipated for charge compensation dominated by Na+, thus suggesting the involvement of protons in the pseudofaradaic mechanism. An important finding o...

2,404 citations

Journal ArticleDOI
TL;DR: In order to fully exploit the potential of manganese oxide-based electrode materials, an unambiguous appreciation of basic questions and optimization of synthesis parameters and material properties are critical for the further development of EC devices.
Abstract: Electrochemical supercapacitors (ECs), characteristic of high power and reasonably high energy densities, have become a versatile solution to various emerging energy applications. This critical review describes some materials science aspects on manganese oxide-based materials for these applications, primarily including the strategic design and fabrication of these electrode materials. Nanostructurization, chemical modification and incorporation with high surface area, conductive nanoarchitectures are the three major strategies in the development of high-performance manganese oxide-based electrodes for EC applications. Numerous works reviewed herein have shown enhanced electrochemical performance in the manganese oxide-based electrode materials. However, many fundamental questions remain unanswered, particularly with respect to characterization and understanding of electron transfer and atomic transport of the electrochemical interface processes within the manganese oxide-based electrodes. In order to fully exploit the potential of manganese oxide-based electrode materials, an unambiguous appreciation of these basic questions and optimization of synthesis parameters and material properties are critical for the further development of EC devices (233 references).

2,110 citations