Pseudocapacitive performance of a solution-processed ß-Co(OH)2 electrode monitored through its surface morphology and area.

In the present study, beta-cobalt hydroxide (ß-Co(OH)2) electrodes of various nanostructures and surface areas, viz. nano-rhombuses (NRs), nano-plates (NPs), and nano-grass (NGs), have been synthesized directly onto a stainless-steel (SS) substrate using a simple, economical and binder-free chemical solution-process, utilizing three cobalt precursor salts, i.e. cobalt acetate, cobalt chloride, and cobalt nitrate, respectively. Structural elucidation proves the crystallite size, type and phase-purity of ß-Co(OH)2, whereas the surface morphology analysis supports the evolution of the above mentioned nanostructures of various surface areas. The electrochemical pseudocapacitor performance investigation demonstrates a specific capacitance (Sc) of 367 F g-1 at 1 mA cm-2 for the NP-type morphology, which is higher than that that displayed by the other morphologies. This change in Sc value is attributed to different charge transfer resistance values, which have been obtained from electrochemical impedance spectroscopy spectra. Finally, we attempt to correlate the relationship between the surface morphology, i.e. surface area, and the charge transfer resistance with the obtained specific capacitance value of the respective electrode.

Nanostructured tin oxide films: Physical synthesis, characterization, and gas sensing properties.

Nanostructured tin oxide (SnO2) films are synthesized using physical method i.e. thermal evaporation and are further characterized with X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy measurement techniques for confirming its structure and morphology. The chemiresistive properties of SnO2 films are studied towards different oxidizing and reducing gases where these films have demonstrated considerable selectivity towards oxidizing nitrogen dioxide (NO2) gas with a maximum response of 403% to 100ppm @200°C, and fast response and recovery times of 4s and 210s, respectively, than other test gases. In addition, SnO2 films are enabling to detect as low as 1ppm NO2 gas concentration @200°C with 23% response enhancement. Chemiresistive performances of SnO2 films are carried out in the range of 1-100ppm and reported. Finally, plausible adsorption and desorption reaction mechanism of NO2 gas molecules with SnO2 film surface has been thoroughly discussed by means of an impedance spectroscopy analysis.

Electrochemical synthesis and potential electrochemical energy storage performance of nodule-type polyaniline.

Nodule-type polyaniline (PAni) has been successfully electrosynthesized onto conducting substrate and envisaged in electrochemical supercapacitor (ES) application as a potential energy storage electrode. Various bands are confirmed from the X-ray photoelectron and Fourier transform infrared spectra. Each nodule is of ∼100-200nminlength and 20-80nmindiameter. The ∼45° surface water contact angle with water of PAni surface can be beneficial for accessing an entire electrode area with minimum interfacial resistance loss when is in contact with the aqueous electrolyte for ES application. The PAni nodule-type electrode when electrochemically characterized using cyclic-voltammetry and galvanostatic charge-discharge measurements has demonstrated a specific capacitance of ∼508Fg-1, a specific energy of 32.12Whkg-1, a specific power of 13.39kWkg-1 and a Coulombic efficiency of 100% in 1MH2SO4 electrolyte solution. An occurrence of 70% retention of initial capacity even after 5000 cycles is supporting for energy-storage application. Two separate redox reaction behaviors are confirmed in the discharge measurement.