Pritam Singh

A novel method for preparation of iron oxyhydroxide materials, involving aqueous precipitation followed by microwave assisted aging is investigated. The produced materials are characterized by XRD, SEM EDX and TEM spectroscopy and BET analysis. The materials show physical characteristics dependent on preparation procedure. The arsenic adsorptive properties of the materials are studied by batch adsorption techniques. It is found that the rate of arsenic upload depends strongly on the degree of crystallinity of the materials. The adsorption capacity is approximately 55 mg/g. The physical characterization of the arsenic loaded adsorbents shows that the adsorption process modifies the morphology of the materials. Over 4% of arsenic atoms are incorporated into the particle matrix.

The availability of an efficient and low cost battery is the key for developing practical electric vehicles (EV). The currently available nickel-metal hydride battery could be a good candidate for EV but it is too expensive and not environmentally acceptable for EV applications. Rechargeable lithium ion batteries that use non-aqueous (organic solvents) electrolytes have been available in the market for over a decade are the most attractive power sources that are vital to meet the challenge of global warming, greenhouse gas emissions and fossil fuel consumption. These can be readily used for powering consumer electronic devices. However, it is quite difficult to make a large lithium battery which is both safe and inexpensive. This is due to the reactivity of the electrode materials with the non-aqueous electrolytes i.e. thermally unstable. In order to realize a perfect safety even at high temperature, non-aqueous (organic) electrolyte may be replaced by aqueous electrolyte system. In the case of non-flammable (aqueous) electrolyte, lithium hydroxide may have an advantage in terms of high conductivity that lowers the charge transfer resistance and cell impedance. The Zn|LiOH|MnO2 battery chemistry reported in this work delivered 142 mAh/g and the cell was rechargeable for multiple cycles. Alternatively, Polyvinylpyrrolidone (PVP) coated MnO2 showed improved discharge capacity of 200 mAh/g but a larger amount of PVP coating causes a decrease in capacity to 83 mAh/g. The incorporation of Bi2O3 + TiS2 (3 wt% each) additives into the MnO2 cathode was found to improve the overall cell performance, this is partly due to the suppression of proton insertion.

The redox behavior and surface characterization of manganese dioxide (MnO2) containing titanium disulphide (TiS2) as a cathode in aqueous lithium hydroxide (LiOH) electrolyte battery have been investigated. The electrode reaction of MnO2 in this electrolyte is shown to be lithium insertion rather than the usual protonation. MnO2 shows acceptable rechargeability as the battery cathode. The influence of TiS 2 (1,3 and 5 wt. %) additive on the performance of MnO2 as a cathode has been determined. The products formed on reduction of the cathode material have been characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). It is found that the presence of TiS2 to ≤ 3 wt. % improves the discharge capacity of MnO 2. However, increasing the additive content above this amount causes a decrease in its discharge capacity.

The redox behavior and surface characterization of manganese dioxide (MnO2) containing titanium boride (TiB2) as a cathode and Zn as an anode have been investigated in aqueous saturated lithium hydroxide (LiOH) electrolyte battery. The electrode reaction of MnO2 with TiB2 in this aqueous electrolyte is shown to be lithium insertion rather than the usual protonation. The influence of TiB2 additive (1, 3 and 5 wt.%) on the performance of MnO2 as a cathode and its cycling ability have been determined.

Intercalation of lithium into the vacant sites of a host compound can be achieved electrochemically using non-aqueous electrolytes. The use of aqueous electrolyte is less common because of the reactivity of many lithium intercalation compounds with water. Here we propose that lithium could be intercalated using aqueous solutions, lithium hydroxide as the electrolyte. The X-ray photoelectron spectroscopy (SIMS) data on the discharged material indicate that lithium is intercalated into the host structure of EMD without the destruction of its core structure. A significant improvement on cell performance was obtained by adding small amounts (<3 wt%) of titanium disulphide (TiS2) to the cathode.

The discharge characteristics of manganese dioxide cathode in the presence of small amounts (1, 3 and 5 wt. %) of titanium disulphide (TiS2) additive has been investigated in an alkaline cell using aqueous lithium hydroxide as the electrolyte. The incorporation of small amounts of TiS2 additives into manganese dioxide (MnO2) was found to improve the battery discharge capacity from 150 to 270 mAh/g. However, increasing the additive from 3 to 5 wt. % causes a decrease in the discharge capacity. Hence, the objective is to gain insight into the role of TiS2 in MnO2 and its mechanism. For this purpose, we have used transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and secondary ion mass spectrometry (SIMS). The valence state determination and the depth profile analysis of the discharged MnO2 were performed using EELS and SIMS techniques.

The electrochemical behavior of lithium manganese phosphate (LIMnPO4) as a cathode material has been investigated in a saturated aqueous lithium hydroxide electrolyte. The crystal structure and surface characterization of the olivine type L1MnPO4 and the products which arc formed on its oxidation and subsequent reduction were studied. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Secondary ion mass spectrometry (SIMS) were used for these investigations. LIMnPO4 is found to be reversibly delithiated on electro oxidation.

2-(11-mercaptoundecyl) [3] (1,1 ')ferrocenophane, BSFc (I) and 3-(11 –mercaptoundecyl) [5] (1,1 ') ferrocenophane, BSFc (II), were synthesized and their electrochemical behaviour in aqueous sulphuric acid electrolyte investigated. It is found that these compounds, chemisorbed on a gold substrate, undergo reversible oxidation/reduction. The anodic and cathodic peak potentials are found to be independent of the acid concentration in the range (1.0x10-2 to 1xI0-7 mol L-1) but change linearly with the acid concentration in the range 1 to SM. While this behaviour is similar to that for other ferrocenes, the materials are much more chemically stable in aqueous sulphuric acid media. The presence of thiol group enhances the retainability of the bridged ferrocenes on gold surface. The possibility of applying this observation for determining state of charge of lead-acid battery is discussed.