Brij Kishore

Electrochemical studies of non-aqueous Na–O2 cells employing Ag-RGO as the bifunctional catalyst

Non-aqueous Na–O2 cells are constructed with Ag-RGO as a bifunctional catalyst. The 10th cycle discharge capacity is 566 mA h g−1 at 0.1 mA cm−2 with coulombic efficiency greater than 80%. XRD, EDAX and XPS studies of the oxygen electrode suggest that NaO2, Na2O2 and Na2O are the discharged products.

One pot green synthesis of MnCO3–rGO composite hybrid superstructure: application to lithium ion battery and biosensor

Herein, hierarchical superstructures of MnCO3 and MnCO3–rGO hybrid nanocomposites with controlled morphologies, such as cube, spherical, dumbbell, and oval, were synthesized via an environmentally friendly hydrothermal treatment using green tea extract (GTE) as a reducing agent as well as a shape controlling agent. During the hydrothermal treatment, the GTE produces carbonate species in the presence of a strong oxidising agent, such as KMnO4, and reduces graphene oxide to graphene. Different superstructures of MnCO3 and MnCO3–rGO were obtained by controlling the reaction time. A tentative growth mechanism for the generation of MnCO3 superstructures is proposed based on the morphologies obtained at different intervals of time. Additionally, MnCO3 and MnCO3–rGO have been used as anode materials for Li-ion batteries. Galvanostatic charge–discharge study shows intercalation/de-intercalation of lithium, which is a characteristic of a battery material. Based on this, it can be concluded that the as-synthesized MnCO3 and MnCO3–rGO with controlled morphologies are important electrode materials for Li-ion batteries. At a current rate of 0.06C, the MnCO3–rGO electrode produces a specific discharge capacity of 340 mA h g−1 after 50 cycles of charge–discharge. MnCO3–rGO is also examined for dopamine (DA) detection using amperometric techniques. Linear current responses were obtained for the DA concentration in the range between 0.2 and 300 μM with 0.999 as the correlation coefficient. The limit of detection (LOD) for DA is found to be 20 nM. The response is not hindered by the presence of other bioanalytes and is reproducible, and the prepared electrodes are stable over a month when stored in a vacuum dessicator.

High capacity MoO3/rGO nanocomposite anode for lithium ion batteries: an intuition into the conversion mechanism of MoO3

MoO3 is a potential anode material for Li-ion batteries (LIBs) because of its high theoretical capacity (1117 mA h g−1). The major hurdles in realizing this high capacity are its low conductivity and large volume variations during intercalation/de-intercalation processes. To mitigate these shortcomings, we have synthesized reduced graphene oxide (rGO) wrapped MoO3 nanoparticles (NPs). This involves the synthesis of MoO3 NPs as the first step and then subjecting the synthesized MoO3 NPs to hydrothermal treatment along with graphene oxide (GO) sheets to form rGO wrapped MoO3 NPs. Electrochemical impedance spectra show that a 13% MoO3/rGO nanocomposite has the least conductive resistance among the different nanocomposites. Several physicochemical characterization techniques have been used to confirm the desired state of the obtained material. Ex-XRD studies were carried out to inspect the mechanism of MoO3 and found that it initially follows a simple lithiation/delithiation mechanism and later it adopts a conversion mechanism. The new architecture exhibits an excellent electrochemical performance by displaying a high first specific discharge capacity value (984 mA h g−1) and remarkable stability (901 mA h g−1 even after 100 cycles).

Composites of Sulfur-Titania Nanotubes Prepared by a Facile Solution Infiltration Route as Cathode Material in Lithium-Sulfur Battery

Achieving high energy density has been the focus of research in rechargeable batteries. Lithiumsulfur system is attractive due to its high theoretical energy density (2500 Wh kg-1). The major problem in Li-S system is associated with the dissolution of lithium polysulfides formed at the cathode during discharge. Shuttling of polysulfides between the cathode and anode during cycling reduces the efficiency of cycling. In the present study, TiO2 nanotubes are prepared from nanoparticles by hydrothermal route. Titania-sulfur composite has been prepared by infiltrating sulfur solution into the TiO2 nanotubes and studied as a cathode material in a non-aqueous electrolyte. Cycling behavior of Li-S cells fabricated using pristine sulfur and TiO2 nanoparticle-sulfur composite is also studied for comparison. Cells with TiO2 nanotubes exhibit better discharge capacity and coulombic efficiency than the cells with TiO2 nanoparticles and pristine sulfur.