Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

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Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Solid State Communications 112 (1999) 383–386

Recent progress and emerging challenges of transition metal sulfides based composite electrodes for electrochemical supercapacitive energy storage

Hydrated Ni(OH)2 and activated carbon based electrodes are widely used in electrochemical applications. Here we report the fabrication of symmetric supercapacitors using Ni(OH)2 nanosheets and activated carbon as positive and negative electrodes in aqueous electrolyte, respectively. The asymmetric supercapacitors stack connected in series exhibited a stable device voltage of 9.6 V and delivered a stored high energy and power of 30 mWh and 1632 mW, respectively. The fabricated device shows an excellent electrochemical stability and high retention of 81% initial capacitance after 100,000 charge-discharges cycling at high charging current of 500 mA. The positive electrode material Ni(OH)2 nanosheets was prepared through chemical decomposition of nickel hexacyanoferrate complex. The XRD pattern revealed the high crystalline nature of Ni(OH)2 with an average crystallite size of ~10 nm. The nitrogen adsorption-desorption isotherms of Ni(OH)2 nanosheets indicate the formation of mesoporous Ni(OH)2 nanosheets. The chemical synthesis of Ni(OH)2 results the formation of hierarchical nanosheets that are randomly oriented which was confirmed by FE-SEM and HR-TEM analysis. The negative electrode, activated porous carbon (OPAA-700) was obtained from orange peel waste. The electrochemical properties of Ni(OH)2 nanosheets and OPAA-700 were studied and exhibit a high specific capacity of 1126 C/g and high specific capacitance of 311 F/g at current density of 2 A/g, respectively. Ni(OH)2 nanosheets delivered a good rate performance and remarkable capacitance retention of 96% at high current density of 32 A/g.

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Fabrication of 9.6 V High-performance Asymmetric Supercapacitors Stack Based on Nickel Hexacyanoferrate-derived Ni(OH)2 Nanosheets and Bio-derived Activated Carbon.

Green and facile synthesis of Ag nanoparticles using Crataegus pentagyna fruit extract (CP-AgNPs) for organic pollution dyes degradation and antibacterial application.

Electrochemical investigation of manganese ferrites prepared via a facile synthesis route for supercapacitor applications

Synthesis of GNS-MnS hybrid nanocomposite for enhanced electrochemical energy storage applications

We report on the influence of hydrogen incorporation on the conductivity of phosphorous (P) doped ZnO thin films grown by using radio-frequency (RF) magnetron sputtering. The P dopant is an oxide form of P2O5, which is introduced into ZnO thin films using RF plasma with oxygen ambient to suppress the generation of O vacancies. The resultant P-doped ZnO thin films were analyzed by means of field-emission scanning electron microcopy (FE-SEM), atomic force microscopy (AFM), secondary ion mass spectroscopy (SIMS), Fourier transform infrared (FT-IR) spectroscopy, photoluminescence and Hall effect measurements. It was observed that the P2O5-doped ZnO thin films annealed at 800 °C exhibited the best electrical property with p-type behavior. Hydrogen atoms in ZnO thin films play an unusual role since it acts as a shallow donor and it may control the n-type conductivity in undoped material. Measurements revealed that the hydrogen atoms can be easily incorporated from the P-doped ZnO sputtering target as the natural hydrogen incorporation in P-doped ZnO thin films during magnetron sputtering. The role of hydrogen atoms incorporated in ZnO thin films is investigated by means of SIMS analysis.

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Hydrogen incorporation effect in phosphorus-doped p-type ZnO thin films grown by radio-frequency magnetron sputtering

Thermoelectric materials that can work at operating temperatures of T ≥ 900 K are highly desirable since the key thermoelectric factors of most thermoelectric materials degrade at high temperatures. In this work, we investigate the high temperature thermoelectric performance of EuFeO3 using a combination of first-principles methods and semi-classical Boltzmann transport theory. High temperature thermoelectric performance is achieved owing to the presence of corrugated flatbands in the valence band region and extremely flatbands in the conduction band region. The lowest energetic structure of EuFeO3 lies within a G-type antiferromagnetic configuration, and the effect of compressive and tensile strains (−7% to +7%) along the (a, b) axes on thermoelectric performance is systematically analyzed. An extremely high value of the Seebeck coefficient (more than 1000 μV/K) is consistently recorded in the high temperature region between 900 K and 1400 K in this material. Furthermore, electrical conductivities and power factors are high and electronic thermal conductivities are low in the considered range of temperatures. The calculated theoretical minimum lattice conductivity is small, estimated at around 1.47–1.54 W m−1 K−1. A compressive strain of −3% is revealed to be the optimum level of strain for enhancing the key thermoelectric factors. Overall, p-type doping shows better thermoelectric performance than n-type doping in EuFeO3.

High thermopower and power factors in EuFeO3 for high temperature thermoelectric applications: A first-principles approach

In this present study, we synthesized a new compound of YbFe2As2 crystals by using a melt growth technique. The YbFe2As2 crystals had been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The presence of oxygen was found by EDAX on the surfaces of grown YbFe2As2 crystals which had been kept in air ambience for few months. The measurement of magnetization (M) versus temperature (T) using a superconducting quantum interference device (SQUID) at constant magnetic field (H = 100 Oe) for oxygen-adsorbed YbFe2As2 (YbFe2As2:O2) had revealed an occurrence of sharp slope change around 140 K. An additional slope change had been observed around 40 K. We had carried out magnetization and transport measurements for oxygen-adsorbed YbFe2As2 (YbFe2As2:O2) and oxygen-adsorbed BaFe2As2 (BaFe2As2:O2) for comparative study also. M versus T data at H = 10,000 Oe had exhibited a paramagnetic behavior for both YbFe2As2:O2 and BaFe2As2:O2. The result of M versus H measurements at 2 K had shown that the saturation had not been achieved for YbFe2As2:O2 at H = 80,000 Oe. There was a slope change observed in transport measurement for YbFe2As2:O2 at 15 K which was not noticed for BaFe2As2:O2.

R. Navamathavan

Papers

Electrochemical investigation of manganese ferrites prepared via a facile synthesis route for supercapacitor applications

Synthesis of GNS-MnS hybrid nanocomposite for enhanced electrochemical energy storage applications

Hydrogen incorporation effect in phosphorus-doped p-type ZnO thin films grown by radio-frequency magnetron sputtering

High thermopower and power factors in EuFeO3 for high temperature thermoelectric applications: A first-principles approach

Investigation of Oxygen-Adsorbed Iron Pnictide Crystals