Browsing by Author "Kumarage, W.G.C."

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    Effect of Seed Layer on Opto-Electronic Properties of CdS Thin Film
    (Uva Wellassa University of Sri Lanka, 2019) Kumarage, W.G.C.; Kumarasinghe, R.K.K.G.R.G.; Wijesundera, L.D.B.R.P.; Seneviratne, V.A.; Jayalath, C.P.; Dassanayake, B.S.
    Among different methods used to grow CdS films, chemical bath deposition (CBD) and electrochemical deposition (ED) are two of the most commonly used techniques. A novel method of growing chemical bath deposited CdS thin films (CBD-CdS) by using electrodeposited CdS (ED-CdS) as a seed layer is reported and compared with conventional ED-CdS and CBD-CdS films in this work. Conventional ED-CdS films were deposited for a duration of 60 min under potentiostatic conditions of -600 mV against the Ag/AgCl electrode at a bath temperature of 60 °C in a reaction solution of 0.05 mol dm-3 cadmium chloride, 0.05 mol dm-3 sodium thiosulfate and diluted H2SO4. Conventional CBD-CdS films were grown using 0.001 mol dm-3 cadmium sulfate, 0.002 mol dm-3 thiourea and 1.1 ml of ammonia solution for a period of 60 min. The seedassisted CBD-CdS films (ED/CBD-CdS) were grown by depositing CBD-CdS on top on an ED-CdS layer deposited for 3 min under the same conditions mentioned above. When compared, the ED/CBD-CdS system showed superior ISC (19.4 µA) performance in PEC cell (CdS/0.1 mol dm-3 Na2S2O3/Pt) compared to other two systems due to its homogeneity, enhanced majority carrier concentration, high surface roughness, and improved inter-particle connections. The ED/CBD-CdS system also showed a significant improvement in VOC (198 mV) over CBD-CdS (169 mV) and ED-CdS (168 mV) systems potentially due to higher flat band potential. Additionally, comparatively high Eg value of 2.45 eV was obtained for the ED/CBD-CdS due to lower disorder value of ED/CBD-CdS system. These results suggest that the novel method of CdS deposition, seed assisted CBD-CdS thin films demonstrate better opto-electronic properties compared to both EDCdS and CBD-CdS films alone.
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    Synthesis of Reduced Graphene Oxide/ Cobalt Oxide Composite as a Super Capacitor Electrode Material Using the Compounds Obtained by Recycling Lithium-Ion Batteries
    (Uva Wellassa University of Sri Lanka, 2020) Samaranayaka, M.N.D.I.R.; Pitawala, H. M. J. C.; Kumarage, W.G.C.
    Today Lithium-ion batteries (LIBs) are widely used in many portable electronic devices, hybrid electric vehicles, and electric vehicles due to their unique features. However, the rapid increment in the disposal of used LIBs to the environment causes severe damages to the environment due to the presence of heavy metals. Thereby environmentally friendly recycling processes are important for LIBs in aspects such as recovering valuable metals from spent LIBs. In this work, a composite electrode material prepared using cobalt oxide (Co3O4) and reduced graphene oxide (rGO) synthesized respectively from cathode and anode material of spent LIBs is described. The battery type considered here was Sony Phone Battery (AGPBO16-A001). Cathode material was subjected to an acid leaching process using 2M H2SO4 along with 10% H2O2 followed by collective precipitation. The pink colour precipitate, obtained at pH 1.5 was confirmed as CoC2O4 using X-ray diffraction technique, Fourier-transform infrared spectroscopy, and X-ray fluorescence data. Subsequently, the annealed sample at 450 0C for 2 hours was undergone with the above tests and conformed as Co3O4 with a crystallite width of 17.7 nm. rGO was synthesized from the anode material using sonication assisted oxidation of graphite. rGO showed an interlayer spacing of 3.4 A0 and a crystallite width of 7 A0 . Composites were prepared on a copper foil by varying the mass ratio of rGO and Co3O4. All the grown samples were examined for cyclic voltammetry measurements in the same photo electrochemical cell. The best electrochemical performance was shown by the composite with the mass ratio of rGO: Co3O4, 1:4. In future methods will be investigated to improve the capacitance of the composite electrode material. Keywords: Lithium-ion Battery, Composite, Acid leaching, Capacitance