Project description:Transition metal oxides, distinguished by their high theoretical specific capacitance values, inexpensive cost, and low toxicity, have been extensively utilized as electrode materials for high-performance supercapacitors. Nevertheless, their conductivity is generally insufficient to facilitate rapid electron transport at high rates. Therefore, research on bimetallic oxide electrode materials has become a hot spot, especially in the field of micro-supercapacitors (MSC). Hence, this study presents the preparation of bimetallic oxide electrode materials via electro-spark machining (EM), which is efficient, convenient, green and non-polluting, as well as customizable. The fabricated copper-molybdenum bimetallic oxide (MoCuOx) device showed good electrochemical performance under the electrode system. It provided a high areal capacity of 50.2 mF cm-2 (scan rate: 2 mV s-1) with outstanding cycling retention of 94.9% even after 2000 cycles. This work opens a new window for fabricating bimetallic oxide materials in an efficient, environmental and customizable way for various electronics applications.
Project description:In this study, we examine the electrochemical performance of supercapacitor (SC) electrodes made from 3D-printed nanocomposites. These composites consist of multiwalled carbon nanotubes (MWCNTs) and polyether ether ketone (PEEK), coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The electrochemical performance of a 3D-printed PEEK/MWCNT solid electrode with a surface area density of 1.2 mm-1 is compared to two distinct periodically porous PEEK/MWCNT electrodes with surface area densities of 7.3 and 7.1 mm-1. To enhance SC performance, the 3D-printed electrodes are coated with a conductive polymer, PEDOT:PSS. The architected cellular electrodes exhibit significantly improved capacitive properties, with the cellular electrode (7.1 mm-1) displaying a capacitance nearly four times greater than that of the solid 3D-printed electrode-based SCs. Moreover, the PEDOT:PSS-coated cellular electrode (7.1 mm-1) demonstrates a high specific capacitance of 12.55 mF·cm-3 at 50 mV·s-1, contrasting to SCs based on 3D-printed cellular electrodes (4.09 mF·cm-3 at 50 mV·s-1) without the coating. The conductive PEDOT:PSS coating proves effective in reducing surface resistance, resulting in a decreased voltage drop during the SCs' charging and discharging processes. Ultimately, the 3D-printed cellular nanocomposite electrode with the conductive polymer coating achieves an energy density of 1.98 μW h·cm-3 at a current of 70 μA. This study underscores how the combined effect of the surface area density of porous electrodes enabled by 3D printing, along with the conductivity imparted by the polymer coating, synergistically improves the energy storage performance.
Project description:We report herein that zinc and cobalt bimetallic-organic-framework (BMOF) crystalline micro-rods are able to be constructed instantly with the eco-friendly glutamate ligand and building unit of double metallic ions. After carbonization and acid leaching of these precursors, the resultant heteroatom-doped porous carbon occupies not only the enriched mesopore architectures but the ultrathin graphitic networks. Moreover, due to cyclizing dehydration reaction of the glutamate ligand upon thermal conversion, the predominant pyrrolic and pyridinic nitrogen atom sites within the carbon lattices are achieved. The supercapacitor electrodes from these carbonaceous materials without any conductive addictive deliver an impressive specific gravimetric capacitance of 230 F g-1 and a specific areal capacitance of 50 μF cm-2 at a current density of 1 A g-1 in alkaline aqueous electrolyte.
Project description:In response to serious ecological and environmental problems worldwide, a novel graphene oxide (GO) induction method for the in situ synthesis of GO/metal organic framework (MOF) composites (Ni-BTC@GO) for supercapacitors with excellent performance is presented in this study. For the synthesis of the composites, 1,3,5-benzenetricarboxylic acid (BTC) is used as an organic ligand due to its economic advantages. The optimum amount of GO is determined by a comprehensive analysis of morphological characteristics and electrochemical tests. 3D Ni-BTC@GO composites show a similar spatial structure to that of Ni-BTC, revealing that Ni-BTC could provide an effective framework and avoid GO aggregation. The Ni-BTC@GO composites have a more stable electrolyte-electrode interface and an improved electron transfer route than pristine GO and Ni-BTC. The synergistic effects of GO dispersion and Ni-BTC framework on electrochemical behavior are determined, where Ni-BTC@GO 2 achieves the best performance in energy storage performance. Based on the results, the maximum specific capacitance is 1199 F/g at 1 A/g. Ni-BTC@GO 2 has an excellent cycling stability of 84.47% after 5000 cycles at 10 A/g. Moreover, the assembled asymmetric capacitor exhibits an energy density of 40.89 Wh/kg at 800 W/kg, and it still remains at 24.44 Wh/kg at 7998 W/kg. This material is expected to contribute to the design of excellent GO-based supercapacitor electrodes.
Project description:This paper describes a simple, reproducible, and scalable procedure for the preparation of a SiO2-containing supercapacitor with high cycle stability. A carbon mesoporous material (CMM) with a high specific surface area, CMK-3, was adopted as an electric double-layer capacitor (EDLC) active material for the preparation of electrodes for the supercapacitor. The optimized SiO2 content decreased as the microsphere diameter decreased, and the optimal specific capacitance was obtained with 6 wt % SiO2 microspheres (100 nm size). The capacitance improved from 133 to 298 F/g. The corresponding capacitance retention rate after 1000 cycles increased from 68.04 to 91.53%. In addition, the energy density increased from 21.05 to 26.25 Wh/kg with a current density of 1 A/g. Finally, similar results based on active carbon, CeO2/CMK-3, and graphene/CNT/MnOv composite electrodes demonstrated that the proposed method exhibits wide compatibility with diverse electrode materials.
Project description:High-surface-area carbon-based capacitors exhibit significant advantages relative to conventional graphite-based systems, such as high power density, low weight, and mechanical flexibility. In this work, novel porous carbon-based electrodes were obtained from commercial cotton fibers (CFs) impregnated with graphene oxide (GO) at different dipping times. A subsequent thermal treatment under inert atmosphere conditions enables the synthesis of electrodes based on reduced GO (RGO) supported on carbon fibers. Those synthetized with 15 min and 30 min of dipping time displayed high specific capacitance given their optimal micro-/ mesoporosity ratio. Particularly, the RGO/CCF15A supercapacitor reports a remarkable specific capacitance of 74.1 F g-1 at 0.2 A g-1 and a high cycling stability with a 97.7% capacitive retention, making this electrode a promising candidate for supercapacitor design. Finally, we conducted a density functional theory study to obtain deeper information about the driving forces leading to the GO/CF structures.
Project description:In recent years, metal oxide-based, inexpensive, stable electrodes are being explored as a potent source of high performance, sustainable supercapacitors. Here, the employment of industrial waste red mud as a pseudocapacitive electrode material is reported. Mechanical milling is used to produce uniform red mud nanoparticles, which are rich in hematite (Fe2O3), and lower amounts of other metal oxides. A comprehensive supercapacitive study of the electrode is presented as a function of ball-milling time up to 15 h. Ten-hour ball-milled samples exhibit the highest pseudocapacitive behavior with a specific capacitance value of ≈317 F g-1, at a scan rate of 10 mV s-1 in 6 m aqueous potassium hydroxide electrolyte solution. The modified electrode shows an extraordinary retention of ≈97% after 5000 cycles. A detailed quantitative electrochemical analysis is carried out to understand the charge storage mechanism at the electrode-electrolyte interface. The formation of uniform nanoparticles and increased electrode stability are correlated with the high performance. This work presents two significant benefits for the environment; in energy storage, it shows the production of a stable and efficient supercapacitor electrode, and in waste management with new applications for the treatment of red mud.
Project description:In recent years, metal oxide-based, inexpensive, stable electrodes are being explored as a potent source of high performance, sustainable supercapacitors. Here, the employment of industrial waste red mud as a pseudocapacitive electrode material is reported. Mechanical milling is used to produce uniform red mud nanoparticles, which are rich in hematite (Fe2O3), and lower amounts of other metal oxides. A comprehensive supercapacitive study of the electrode is presented as a function of ball-milling time up to 15 h. Ten-hour ball-milled samples exhibit the highest pseudocapacitive behavior with a specific capacitance value of ≈317 F g-1, at a scan rate of 10 mV s-1 in 6 m aqueous potassium hydroxide electrolyte solution. The modified electrode shows an extraordinary retention of ≈97% after 5000 cycles. A detailed quantitative electrochemical analysis is carried out to understand the charge storage mechanism at the electrode-electrolyte interface. The formation of uniform nanoparticles and increased electrode stability are correlated with the high performance. This work presents two significant benefits for the environment; in energy storage, it shows the production of a stable and efficient supercapacitor electrode, and in waste management with new applications for the treatment of red mud.
Project description:Novel hybrid nanomaterials comprising metal-organic framework compounds carbonised in the presence of biomass material derived from rice husk have been investigated as a new class of sustainable supercapacitor materials for electrochemical energy storage. Specifically, two synthetic routes were employed to grow Co/Mn metal-organic framework compounds in the channels of rice husks, which had been activated previously by heat treatment in air at 400 °C to produce a highly porous network. Pyrolysis of these hybrid materials under nitrogen at 700 °C for 6 h produced metal-containing phases within the nanocarbon, comprising intimate mixtures of Co, MnO and CoMn2O4. The materials thus produced are characterized in detail using a range of physical methods including XRD, electron microscopy and X-ray photoelectron spectroscopy. The synthetic pathway to the metal-organic framework compound is shown to influence significantly the physical properties of the resulting material. Electrochemical evaluation of the materials fabricated revealed that higher specific capacitances were obtained when smaller crystallite sized bimetallic Co/Mn-MOFs were grown inside the rice husks channels compared to larger crystallite sizes. This was in-part due to increased metal oxide loading into the rice husk owing to the smaller crystallite size as well as the increased pseudocapacitance exhibited by the smaller crystallite sizes and increased porosity.
Project description:A template-free and one-step carbonization process was developed for fabricating graphitic porous carbon spheres (GPCSs) on hemicelluloses as the electrode material for supercapacitors. This method is green, low-energy, and less time consuming compared to the conventional two-step process (pore-forming and graphitizing). It uses K2FeO4, a mild activating agent that fulfills synchronous activation and graphitization. The GPCSs is regular spherical shape, have high nanoporosity, a large specific surface area (1,250 m2 g-1), and have a high graphitization degree. A unique structural advantage includes a rich interconnected conductive network for electron transfer that shortens the ion transport distance of the electrolyte. Remarkably, the GPCSs electrode displays outstanding electrochemical performance including high specific capacitance (262 F g-1 at 1.0 A g-1), rate capability energy (80%, 20 A g-1), and excellent cycling stability (95%, 10,000 cycles). This work represents a powerful methodology to develop sustainable and low-cost energy storage devices from hemicellulose.