HYBRID NANOSTRUCTURED MATERIALS FOR SUPERCAPACITORS

School of Molecular Sciences(Chemistry)clos

Improvement of dye-sensitized solar cells toward the broader light harvesting of the solar spectrum

Dye-sensitized solar cells (DSSCs) have been extensively evolved for the past two decades in order to improve their cell performance. From the commercialization point of view, the overall solar to electrical energy conversion efficiency should compete with other solar cells. But, due to structural restrictions of DSSC using the liquid electrolyte and a space requirement between two electrodes, the direct tandem construction of DSSCs by stacking of repeating units is highly limited. In this feature article, important research trials to overcome these barriers and a recent research trend to improve the light harvesting strategies mainly panchromatic engineering, various tandem approaches such as parallel tandem, series tandem, p-n tandem etc., have been briefly reviewed.close271

Molybdenum diselenide/reduced graphene oxide based hybrid nanosheets for supercapacitor applications

In the present study, molybdenum diselenide/reduced graphene oxide (MoSe2/rGO) nanosheets were synthesized via a facile hydrothermal process and the electrochemical performance of the nanosheets was evaluated for supercapacitor applications. The MoSe2 nanosheets were uniformly distributed on the surface of the rGO matrix. The MoSe2/rGO nanosheet electrode exhibited an enhanced specific capacitance (211 F g-1) with excellent cycling stability, compared with pristine MoSe2. The enhanced electrochemical performance of the MoSe2/rGO nanosheet electrode is mainly attributed to the improved electron and ion transfer mechanism involving the synergistic effects of pseudocapacitance (from the MoSe2 nanosheets) and the electric double layer charge (EDLC, from the rGO nanosheets) storage behavior. These results demonstrate that the enhanced electrochemical performance of MoSe2/rGO nanosheets could be obtained via a facile and scalable approach.clos

Few-layered MoSe2 nanosheets as an advanced electrode material for supercapacitors

We report the synthesis of few-layered MoSe2 nanosheets using a facile hydrothermal method and their electrochemical charge storage behavior. A systematic study of the structure and morphology of the as-synthesized MoSe2 nanosheets was performed. The downward peak shift in the Raman spectrum and the high-resolution transmission electron microscopy images confirmed the formation of few-layered nanosheets. The electrochemical energy-storage behavior of MoSe2 nanosheets was also investigated for supercapacitor applications in a symmetric cell configuration. The MoSe2 nanosheet electrode exhibited a maximum specific capacitance of 198.9 F g(-1) and the symmetric device showed 49.7 F g(-1) at a scan rate of 2 mV s(-1). A capacitance retention of approximately 75% was observed even after 10 000 cycles at a high charge-discharge current density of 5 A g(-1). The two-dimensional MoSe2 nanosheets exhibited a high specific capacitance and good cyclic stability, which makes it a promising electrode material for supercapacitor applications

Amorphous MoSx thin-film-coated carbon fiber paper as a 3D electrode for long cycle life symmetric supercapacitors

Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm-2, while it was 41.9 mF cm-2 for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles.clos

Hematite microdisks as an alternative anode material for lithium-ion batteries

In this work, hematite microdisks (500 nm to 1 μm in diameter, ∼200 nm in thickness) have been synthesized by a facile hydrothermal method which exhibited good cycling stability at a current density of 200 mA g−1 and 1000 mA g−1, and excellent rate performance at various current densities ranging from 100 mA g−1 to 4000 mA g−1.acceptedVersio

Comprehensive insight into the mechanism, material selection and performance evaluation of supercapatteries

Electrochemical energy storage devices (EESs) play a crucial role for the construction of sustainable energy storage system from the point of generation to the end user due to the intermittent nature of renewable sources. Additionally, to meet the demand for next-generation electronic applications, optimizing the energy and power densities of EESs with long cycle life is the crucial factor. Great efforts have been devoted towards the search for new materials, to augment the overall performance of the EESs. Although there are a lot of ongoing researches in this field, the performance does not meet up to the level of commercialization. A further understanding of the charge storage mechanism and development of new electrode materials are highly required. The present review explains the overview of recent progress in supercapattery devices with reference to their various aspects. The different charge storage mechanisms and the multiple factors involved in the performance of the supercapattery are described in detail. Moreover, recent advancements in this supercapattery research and its electrochemical performances are reviewed. Finally, the challenges and possible future developments in this field are summarized

Freeze-dried MoS2 sponge electrodes for enhanced electrochemical energy storage

In the present study, we have synthesized high surface area MoS2 sponge electrodes via a facile hydrothermal method followed by a freeze drying process. The performance of the MoS2 based symmetric capacitor showed a high specific capacitance value of around 128 F g(-1) at a scan rate of 2 mV s(-1), and also a single electrode showed a specific capacitance of 510 F g(-1), which is a remarkable value to be reported for a MoS2 based material in a symmetric device configuration. Also, a high energy density of around 6.15 Wh kg(-1) and a good cyclic stability over 4000 cycles are obtained for the symmetrical cell.clos

Fabrication of panchromatic dye-sensitized solar cells using pre-dye coated TiO2 nanoparticles by a simple dip coating technique

An appropriate method of pre-dye coating of TiO2 nanoparticles (NPs) and a facile approach of a dip coating technique have been adopted for the fabrication of panchromatic dye-sensitized solar cells (DSSC). A bi-layer photoanode consists of two distinct layers of TiO2 films, which were individually sensitized with N719 and N749 dyes and then coated on a TCO substrate in a sequenced manner. The spectral response of panchromatic DSSCs has been investigated using monochromatic incident photon to current conversion efficiency (IPCE) spectroscopy. The IPCE spectrum of panchromatic DSSC revealed the absorption characteristics of each single dye cell. The broader absorption spectra were obtained up to 850 nm of near IR region and the higher quantum efficiency than those of single cells were recorded. The higher value of IPCE is correlated with the higher short circuit current density value of panchromatic cell (J(sc) = 13.4 mA cm(-2)). The tandem cell showed an average open circuit voltage (V-oc = 0.79 V) of the single dye cells with an overall conversion efficiency of 7.1%. Moreover, the present approach does not require any high temperature sintering process; therefore it could be suitable for the fabrication of flexible panchromatic DSSCs.close3

Nanomaterials for Electrochemical Energy Conversion and Storage Technologies

In this modern era, our society faces a serious energy crisis due to increasing human population. Energy consumption starts from small-scale electronic gadgets to high power consuming electric vehicles. To supply power on demand, researchers focus on alternative renewable energy resources including solar energy, wind energy, hydropower, geothermal energy, and bioenergy. Effectively, energy conversion and storage technologies such as solar cells, fuel cells, secondary batteries, supercapacitors, and other self-powered systems are under rigorous investigation. The efficient energy conversion and storage performance of those technologies rely on material properties of their electrode, electrolyte, and other device components. It is recently known that nanostructuring of device components leads to enhanced efficiency in terms of robustness and reliability of the energy conversion and storage systems. Moreover, the nanostructured materials have attracted great interest due to their unique physicochemical and electrochemical properties. Hence, the utilization of such materials in nanodimensions will create enormous impact on the efficiency of various energy conversion and storage devices. The main objective of this special issues is to identify the significant research paradigms of nanomaterials and their potential impacts on applications. In particular, focus of this issue is on the synthesis and characterization of nanostructured materials for various applications such as supercapacitors, batteries, photoelectrochemical, and thermal enhancement systems. The highlights of the published articles are summarized as follows. In this special issue, Y. Yuan et al. synthesized the porous activated carbon materials from Pleurotus eryngii-based biomass material via carbonization, followed by KOH activation and utilized it for supercapacitor applications. The as-prepared activated carbon presented a large specific area with high porosity which exhibited a maximum specific capacitance of 195 F g-1 with 93% capacitance retention after 15000 cycles. It is known that Pleurotus eryngii is one of the readily available sources of carbon materials, potentially suitable for supercapacitor applications. Also, this biomass can be the resource for development of porous activated carbon for other energy conversion and storage devices in the future. Further, B.-X. Zou et al. synthesized hierarchical porous N, O-doped carbon composites by combining low molecular weight phenol resin and silk fibers in various combinations using a hydrothermal method and carbonization process. The as-prepared electroactive materials showed a low resistance and good surface area with hierarchical porosity. The low molecular phenol resin and silk fiber combination increases the surface area and enhanced the electron transport within the active materials. The fabricated symmetric device delivered a maximum energy density of 7.4 Wh kg-1 and power density of 90.1 W kg−1 using aqueous electrolyte