D.S. Dhawale

Conversion of Chemically Prepared Interlocked Cubelike Mn3O4 to Birnessite MnO2 Using Electrochemical Cycling

Interlocked cubelike Mn3 O4 thin films have been prepared by a simple and low temperature chemical bath deposition method. These interlocked cubelike Mn3 O4 thin films are further converted into nanoflakes of birnessite MnO2 using voltammetric cycling in aqueous Na2 SO4 electrolyte. The process is dynamic potential activated, which causes the formation of sheet-shaped nanoflakes. The films are characterized by X-ray diffraction, field-emission-scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform IR spectrum, and wettability test. Impedance spectroscopy studies revealed that charge-transfer resistance of the birnessite MnO 2 structure has a lower value than that of the Mn3 O 4 structure. The effect of different numbers of potential cycles on structure, surface morphology, valence states, and contact angles has been investigated. During the cycling process, the supercapacitance of manganese oxide increased by more than 10 times. The maximum supercapacitance achieved at 5 mV s-1 is 223 F g-1. The effect of scan rate on the specific capacitance of birnessite MnO2 electrode has been studied.

Porous CuO nanosheet clusters prepared by a surfactant assisted hydrothermal method for high performance supercapacitors

This investigation demonstrates the surfactant assisted fabrication of nanosheet clusters of caddice clew, yarn ball and cabbage slash-like microstructures of copper oxide (CuO) in thin film form directly grown onto a stainless steel substrate using a binder free hydrothermal approach. The impact of organic surfactants such as Triton X-100 (TRX) and polyvinyl alcohol (PVA) on the structural, morphological, surface area and electrochemical properties of CuO is investigated. The X-ray diffraction study reveals the structure-directing ability of the organic surfactants and confirms the nanocrystalline nature of the CuO thin films. Additionally, these CuO microstructures show excellent surface properties like uniform surface morphology, good surface area and a uniform pore size distribution. The electrochemical tests manifest a high specific capacitance of 535 F g−1 at a scan rate of 5 mV s−1 with 90% capacitive retention after 1000 cycles and low dissolution and charge transfer resistance of the yarn ball-like structured CuO thin film. This approach renders a plain picture of the process–structure–property relationship in thin film synthesis and provides significant schemes to boost the performance of supercapacitor electrodes.

TiO2 Nanorods Decorated with Pd Nanoparticles for Enhanced Liquefied Petroleum Gas Sensing Performance

Development of highly sensitive and selective semiconductor-based metal oxide sensor devices to detect toxic, explosive, flammable, and pollutant gases is still a challenging research topic. In the present work, we systematically enhanced the liquefied petroleum gas (LPG) sensing performance of chemical bath deposited TiO2 nanorods by decorating Pd nanoparticle catalyst. Surface morphology with elemental mapping, crystal structure, composition and oxidation states, and surface area measurements of pristine TiO2 and Pd:TiO2 nanorods was examined by high resolution transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption characterization techniques. LPG sensing performance of pristine TiO2 and Pd:TiO2 nanorods was investigated in different LPG concentration and operating temperature ranges. The LPG response of 21% for pristine TiO2 nanorods is enhanced to 49% after Pd catalyst decoration with reasonably fast response and recovery times. Further, the sensor exhibited long-term stability, which could be due to the strong metal support (Pd:TiO2) interaction and catalytic properties offered by the Pd nanoparticle catalyst. The work described herein demonstrates a general and scalable approach that provides a promising route for rational design of variety of sensor devices for LPG detection.