R.B. Pujari

Bath temperature controlled phase stability of hierarchical nanoflakes CoS2 thin films for supercapacitor application

In the present study, CoS2 thin-film electrodes are synthesized at different bath temperatures using a simple chemical bath deposition (CBD) method. The bath temperature controls the phase stability of the CoS2 thin film along the in-plane direction up to 353 K. However, at 363 K, an oxide phase is included in the film. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies showed enhanced crystallinity of CoS2 as the bath temperature increased and evolution in surface morphology from immature nanoflakes to well-grown aligned mature nanoflakes. A specific capacitance of 800 F g−1 is obtained from cyclic voltammetry measurements by utilizing the 83.6 m2 g−1 surface area of CoS2 nanoflakes synthesized at 353 K. The hierarchical distribution of pores gives rise to a high specific energy and specific power of 40.74 W h kg−1 and 3333 W kg−1, respectively, as a result of utilization of the high electrochemically active surface area. Furthermore, good long-term cycling stability of CoS2 nanoflakes has been observed in a 2 M KOH electrolyte. A low impedance value suggests that the CoS2 nanoflake electrode prepared by a facile CBD method is a potential candidate for supercapacitor application.

The synthesis of multifunctional porous honey comb-like La2O3 thin film for supercapacitor and gas sensor applications

The porous honey comb-like La2O3 thin films have been synthesized using one step spray pyrolysis method. The influence of sprayed solution quantity on properties of La2O3 thin films is studied using X-ray diffraction, Fourier transform spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, optical absorption and Brunauer-Emmett-Teller techniques. Morphology of La2O3 electrode is controlled with sprayed solution quantity. The supercapacitive properties of La2O3 thin film electrode are investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance techniques. The La2O3 film electrode exhibited the specific capacitance of the 166Fg-1 with 85% stability for the 3000 cycles. The La2O3 film electrode exhibited sensitivity of 68 at 523K for 500ppm CO2 gas concentration. The possible CO2 sensing mechanism is discussed.

Chemically deposited nano grain composed MoS2 thin films for supercapacitor application

Low temperature soft chemical synthesis approach is employed towards MoS2 thin film preparation on cost effective stainless steel substrate. 3-D semispherical nano-grain composed surface texture of MoS2 film is observed through FE-SEM technique. Electrochemical supercapacitor performance of MoS2 film is tested from cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) techniques in 1M aqueous Na2SO4 electrolyte. Specific capacitance (Cs) of 180Fg-1 with CV cycling stability of 82% for 1000 cycles is achieved. Equivalent series resistance (Rs) of 1.78Ωcm-2 observed through Nyquist plot shows usefulness of MoS2 thin film for charge conduction in supercapacitor application.

Modification in supercapacitive behavior of CoO-rGO composite thin film from exposure to ferri/ferrocyanide redox active couple

Present work demonstrates enhanced supercapacitive performance of CoO-rGO electrode using redox electrolyte. The long range electrostatic force developed during deposition of CoO-rGO composite thin film orient the molecules into the hexagonal crystal structure. The incorporated CoO particles into rGO nano-sheets make the structure more porous for the intercalation of the electrolyte ions through the electrode material. Additionally, 0.025 M K3[Fe(CN)6] + 0.025 M K4[Fe(CN)6] redox couple into KOH electrolyte enhances the supercapacitive performance than bare KOH electrolyte. The maximum specific capacitance of 1005 F g-1 is observed due to the combined effect of K3[Fe(CN)6] and K4[Fe(CN)6] redox couple into KOH electrolyte. Also, energy density of 86.74 Wh kg-1 at power density of 3.54 kW kg-1 suggest potential application of CoO-rGO composite thin film in the development of high energy density supercapacitor based on redox active electrolyte.

Cobalt sulfide thin films for electrocatalytic oxygen evolution reaction and supercapacitor applications

Nanocrystalline cobalt sulfide thin film electrodes have been deposited on stainless steel substrate using binder-free chemical bath deposition (CBD) method and electrochemical study is performed in 1 M KOH electrolyte. Linear sweep voltammetry (LSV) curve shows that cobalt sulfide thin film electrode requires 300 mV overpotential (ƞ) to reach the current density of 10 mA cm-2. Also, it exhibits Tafel slope of 57 mV decade-1 with stable catalytic activity over 14 h. Along with good electrocatalytic oxygen evolution performance, in supercapacitive study it shows specific capacitance of 252.39 F g-1 at a scan rate of 5 mV s-1. The stability test indicates that cobalt sulfide electrode is stable for 1000 cyclic voltammetry (CV) cycles.