Browsing by Author "Wijesundara, L. B. D. R. P."

Now showing 1 - 4 of 4

Electrodeposited p-type copper oxide for lithium-ion battery applications
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Millamadiththa, S. V.; Jayathilaka, K. M. D. C.; Wijesundara, L. B. D. R. P.
Lithium-ion batteries (LIBs) are considered a promising energy storage device due to their energy density, capacity, and longevity. In recent years, transition metal oxides have gained greater attraction due to their high theoretical capacity for rechargeable battery applications. The development of the anode and cathode in rechargeable batteries is crucial for enhancing overall battery performance. Among the different types of alternative anode materials for LIBs, Cu₂O is crucial due to its high specific capacity, low cost, environmental benefits, and ease of production. In this investigation, growth and characterization of p-Copper Oxide were carried out for possible anode material for rechargeable battery applications. Electrodeposition of p-Copper Oxide was carried out potentiostatically in a threeelectrode electrochemical cell containing 3M lactic acid 0.04M cupric sulfate (CuSO4) and 3M sodium hydroxide (NaOH) at - 450 mV vs Ag/AgCl for 30 min. The pH of the bath was adjusted to 12.5 using sodium hydroxide and bath temperature and stirring speed were maintained at 60°C and 200 rev./min respectively during the deposition. Titanium plate, Ag/AgCl, and platinum plate were used as working electrode, reference electrode, and counter electrode respectively. Grown materials were characterized using High Energy X-ray Diffraction (HEXRD), FTIR, Scanning Electron Microscopy (SEMs), MottSchottky measurements, and charge-discharge measurements. The HEXRD spectrum exhibited all the peaks corresponding to the reflection from Cu2O and CuO. Thus, HEXRD results revealed that the grown thin films (≈1 µm) consist of polycrystalline Cu2O with a cubic crystal structure and CuO with a monoclinic crystal structure indicating the formation of copper oxide. The FTIR spectra exhibited peaks related to Cu-O stretching vibrations and -OH groups, confirming the growth of Cu2O having proper composition. The SEM analysis confirmed the formation of uniform polycrystalline cubic grain morphology Cu2O having grain size in the order of 100-300 nm. Mott-Schottky analysis confirmed the p-type conductivity of Cu₂O having a doping density around 3.30×1016 cm⁻³ which is crucial for efficient conversion reactions during battery operation. The fabricated device using p-Copper Oxide as anode material exhibited a specific capacity of 205.4 mAh g-1. Overall results of this study reveal that electrodeposited p-Copper Oxide improves the interfacial properties between the anode and current collector and electrolyte. In conclusion, electrodeposited p-Copper Oxide can be used as a promising anode material for high-performance LIBs.
Fabrication and characterization of sulfur-treated cuprous oxide-based supercapacitors
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wijesinghe, W. A. N. D.; Jayathilaka, K. M. D. C.; Ranaweera, A. L. A. K.; Wijesundara, L. B. D. R. P.; Kalingamudali, S. R. D.
Supercapacitors are crucial for modern energy storage, offering high power density, fast charging, and life spans. They are widely used in various applications, meeting the need for lightweight, flexible, and eco-friendly energy solutions. Cuprous oxide (Cu2O) holds significant promise as an electrode material for supercapacitors owing to its distinctive properties. However, electrodeposited Cu2O films often have high resistivity and surface defects, hampering their electrochemical performance. To address this issue, sulfur treatment was employed to modify the surface properties of Cu2O electrodes, aiming to enhance their electrochemical performance. In this research, sulfur-treated Cuprous-oxide thin films were used as the supercapacitor electrodes, and PVA-KOH gel polymer was employed as the supercapacitor separator and electrolyte. The Cu2O films were synthesised on a Ti substrate via electrodeposition, followed by Ammonium Sulfide (NH4)2S vapour treatment for surface modification, with varying exposure times. Untreated Cu2O thin films were analysed for comparison. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to examine their structural and surface morphological characteristics. The XRD analysis showed that the Cu2O deposited on the Ti substrate treated with (NH4)2S vapour did not yield distinct CuxS peaks, indicating the formation of a very thin or amorphous CuxS layer on the film surface. SEM revealed an altered morphology of the electrodeposited Cu2O thin films after the (NH4)2S vapour treatment, with the development of a non-uniform additional layer on the surface. The electrochemical performance of sulfur-treated Cu2O electrodes for supercapacitors was studied using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS). Sulfur-treated electrodes exhibited enhanced performance, showing higher specific capacitance, energy density, and power density compared to untreated electrodes. The supercapacitor utilising sulfur-treated Cu2O deposited on the Ti electrodes, treated for 10 s, demonstrated superior performance with a specific capacitance of 773.81 mF/g, energy density of 154.76 mWh/kg, and power density of 111.43 W/kg. Conversely, the untreated electrode-based supercapacitor exhibited lower values, with a specific capacitance of 23.34 mF/g, energy density of 4.67 mWh/kg, and power density of 3.38 W/kg. In summary, this study explored the impact of sulfur treatment on the electrochemical performance of electrodeposited Cu2O. CV, GCD, and EIS analyses revealed improved electrochemical performance due to the reduction of surface defects with (NH4)2S surface treatment. The results indicated that the best performance can be obtained in Cu2O with a 10 s (NH4)2S exposure duration for application in supercapacitors.
Ionic conductivity of novel solid polymer electrolyte based on polyethylene oxide (PEO) and magnesium pyrophosphate (Mg2P2O7)
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Lakshan, K. L. A. C.; Sumathipala, H. H.; Wijesundara, L. B. D. R. P.
Lithium-ion batteries were hailed as a breakthrough solution for energy storage, revolutionizing portable electronics, electric vehicles, and other applications. However, as their implementation expanded, certain drawbacks came to light. Issues such as limited energy density, safety concerns, and the scarcity and high cost of lithium resources highlighted the need for a replacement. Researchers turned their attention to alternative materials, with sodium being a promising candidate due to its abundance. However, its high reactivity posed significant challenges. The search for a viable alternative led scientists to explore magnesium-based electrolytes. Lithium and magnesium are almost similar in ionic radii, presenting an exciting opportunity for further research. In this Investigation, the focus was on synthesizing and characterizing a novel magnesium ionbased solid polymer electrolyte. Polyethene oxide (PEO) was chosen as the polymer host, and magnesium pyrophosphate (Mg2P2O7) as the dopant salt. By varying the amount of salt while keeping the same amount of PEO, five different types of electrolytes were made: PEO5Mg2P2O7, PEO10Mg2P2O7, PEO15Mg2P2O7, PEO20Mg2P2O7, and PEO25Mg2P2O7. The hot-pressed technique was used to fabricate the solid polymer electrolytes, and the resulting materials were characterized in the frequency range of 1Hz to 1 MHz using the Gamry framework version 6.11. Arrhenius plots were derived from Nyquist plots to study the conductivity variation with temperature. The temperature range for the study spanned from 25°C to 100°C. The characterization results revealed that among the different electrolyte samples, PEO10Mg2P2O7 demonstrated the highest electrical conductivity of 5.0×10-6 Scm-1 at 50°C. This temperature was selected since the melting point of PEO is 64 °C. This value of conductivity is comparatively lower than most existing magnesium ion-based solid polymer electrolytes. The results from this study pave the way for further investigations and improvements. Incorporating fillers could enhance the conductivity of the electrolyte material and improve its overall performance. Such advancements may yield even more promising results, making magnesium-based solid polymer electrolytes viable candidates for solid-state batteries. Alternatively, a gel polymer might give a more promising result than a solid polymer.
The role of ascorbic acid in optimizing optoelectronic performances of CdS thin films
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Danansuriya, D. B. U. I.; Hetti Arachchige, K. A.; Manilgama, T. T. D.; Kalingamudali, S. R. D.; Premaratne, W. A. P. J.; Jayathilaka, K. M. D. C.; Wijesundara, L. B. D. R. P.; Kumarage, W. G. C.
Cadmium sulfide (CdS), a widely studied (II-VI) group semiconductor, has long captivated the scientific community due to its potential applications in photovoltaic (PV) devices. However, optoelectrical properties of n-CdS, such as flat band potential, and optical band gap, are crucial for enhancing solar cell efficiency. This study explores the tunability of these properties in CdS thin films through chemical bath deposition (CBD) with a mild reducing agent ascorbic acid (C6H8O6). A series of CdS thin films were deposited on fluorine-doped tin oxide (FTO) glass substrates by using various concentrations of ascorbic acid (0, 0.1, 0.01, and 0.001 mol.dm-3). The deposition chemical bath consisted of 0.1 mol.dm-3 cadmium sulfate (CdSO4) and 0.2 mol.dm-3 thiourea (CS(NH2)2) as cadmium and sulfur sources, respectively. The deposition process was conducted at 80 °C for one hour at a pH of 11. Post-deposition, the CdS films were etched in the non-conductive side of the FTO with diluted hydrochloric acid (HCl), followed by annealing at 300 °C for one hour in air. All the electrical measurements were performed in a photoelectrochemical cell comprising a CdS/0.1 mol.dm-3 Na2S2O3/Pt half-cell with an active area of 1 cm². An Ag/AgCl electrode served as the reference for all characterizations. The short-circuit current density (JSC) has shown a significant increase with decreasing ascorbic acid concentration, achieving a 155.6% enhancement with a concentration of 0.001 mol.dm-3 compared to untreated CdS. Conversely, with increasing ascorbic acid concentration the opencircuit voltage (VOC) and the flat band potential (VFB) decreased. The highest reported photocurrent power (VOC×ISC) was observed in films deposited with 0.001 mol.dm-3 ascorbic acid, showing a 150.2% improvement over untreated CdS. Scanning electron microscopy (SEM) analysis revealed that ascorbic acid-treated CdS films exhibited aggregated nanoscale particles, whereas untreated films displayed larger clusters. Consequently, the photocurrent enhancement is attributed to these morphological changes that cause higher effective surface area in the ascorbic-treated CdS thin films compared to the untreated CdS. Furthermore, Mott-Schottky analysis confirmed that all deposited films retained n-type characteristics. This study demonstrates that the electronic properties of n-CdS can be finely tuned through ascorbic acid treatment, making it a promising approach for fabricating thin film solar cells with high light-to-current conversion efficiency. The ability to control and enhance these properties is invaluable for advancing PV applications and achieving higher solar cell performances.