Loading...
Search for: electrochemical-impedance-spectroscopy
0.013 seconds
Total 165 records

    Design of Doped TiO2 Dye-sensitized Solar Cells with Different Arrangement Modes of Photoanode Electrodes

    , M.Sc. Thesis Sharif University of Technology Vafaei, Maral (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge.... 

    Synthesis, Characterization and Investigation of Electrocatalytic Activity of Nanoparticle/Cerium Oxide Composites in Oxygen Evolution and Reduction Reactions

    , M.Sc. Thesis Sharif University of Technology Moravvej, Heydar (Author) ; Taherinia, Davood (Supervisor)
    Abstract
    The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

    Synthesis, Characterization and Investigation of Electrocatalytic Activity of Nanoparticle/Cerium Oxide Composites in Oxygen Evolution and Reduction Reactions

    , M.Sc. Thesis Sharif University of Technology Moravvej, Heydar (Author) ; Taherinia, Davood (Supervisor)
    Abstract
    The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

    Synthesis and Characterization of Supercapacitor Electrodes Based on Graphene and MnO2 Nanostructure

    , M.Sc. Thesis Sharif University of Technology Mardi, Saeed (Author) ; Moshfegh, Alireza (Supervisor) ; Moradlou, Omran (Co-Advisor)
    Abstract
    Supercapacitors represent a new class of energy storage devices that have been attracted many researchers in last few years. Graphene with unique properties such as superior electrical conductivity and large specific surface area is one of the most suitable materials in supercapacitor applications. Besides, metal oxides are being used as active compounds in supercapacitors due to their role in redox reactions. In this research, synthesis and characterization of supercapacitor electrodes based on graphene and MnO2 nanostructured materials was studied under different conditions. For this purpose, Graphene oxide (GO) was synthesized by Hummers’ method and then, it was deposited on a nickel foam... 

    Preparation and Characterization of a Lithium Ion Conducting Electrolyte

    , M.Sc. Thesis Sharif University of Technology Toofan, Samin (Author) ; Nemati, Ali (Supervisor)
    Abstract
    In recent years lithium-air batteries captured worldwide attention because of their high energy density. Solid state electrolytes is one of the main components of lithium-air batteries. Lithium almunium titanium phosphate(LATP) is a nasicon type ion conduction which may be of great potential as solid electrolyte. The object of this thesis was the preparation of LATP solid electrolyte which can be used in a lithium-air battery. To reach this goal LATP powder was synthesized using a solution-based method and an appropriate crystallization temperature was selected based on obtained results of X-ray diffraction analysis. In the next step solid electrolytes was prepared under different pressing... 

    Electrochemical Hydrogen Generation Using Metal Organic Frameworks Derived Catalysts

    , M.Sc. Thesis Sharif University of Technology Koohdareh, Amir Reza (Author) ; Gholami, Mohamad Reza (Supervisor)
    Abstract
    In recent years, the widespread investigation on multi-transition metal oxides that with two or more transition metal oxides, have been increased rapidly for electrochemical application due to low cost, high conductivity and good electrochemical performance other than single metal oxides. In this project, CuCo2O4 nanoparticles were firstly fabricated by decomposing of CuCo-MOF as the template. The as prepared samples were used to synthesis a new nanocomposite of MoS2 and CuCo2O4. The best ratio of the two component were optimized to prepare the best electrocatalyst for Hydrogen evolution reaction (HER). The structure of prepared nanocomposite were investigated by various techniques such as... 

    Synthesis of Carbon Nanostructure-Metal Nanoparticles Composites and Investigate their Application as a Modifier in Electrochemical Mesurments

    , Ph.D. Dissertation Sharif University of Technology Hosseininassab, Niloufar (Author) ; Shahrokhian, Saeed (Supervisor)
    Abstract
    In the first part, metallic nanoparticles were synthesized on the different carbon nanostructers platform such as nanodiamond and graphene sheet using electrochemical and chemical methods. The prepared composite film were characterized by electron microscopy, spectroscopy and electrochemical techniques. The synthesized nanocomposite were applied as a modifier in order to prepare electrochemical sensors for determination trace amount of important pharmaceutical and biological compounds.In the first work, Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was synthesized with chemical method. The surface morphology and the nature of the composite were investigated. The... 

    Theoretical Determination of the Impedance Response of Some General Multi Step Electrode Processes

    , M.Sc. Thesis Sharif University of Technology Rash Seyedabadi, Hazhar (Author) ; Gobal, Fereydoon (Supervisor)
    Abstract
    Impedance measurement is one of the most efficient electrochemical methods to investigate the mechanism and kinetics of electrode reactions. This method can detect the steps of successive or parallel electron and mass transfer chemical reactions based on measuring the response time constant. The method of showing results, commonly known as Nyquist diagram,which is based on drawing real and imaginary components of the impedance, with respect to each other in different measurement frequencies, is very useful for determining the mechanism of electrode reactions and the kinetic measurements. The main objective of this thesis is totheoretically determine the impedance response of six... 

    Investigation of Electrocatalytic Activity of Metal-based Nanocomposites in the Reaction of Carbon Dioxide Reduction

    , M.Sc. Thesis Sharif University of Technology Hatami, Homayoun (Author) ; Bastani, Darioush (Supervisor) ; Taherinia, Davood (Supervisor)
    Abstract
    Emissions of carbon dioxide (CO2) from fossil fuels are a potential issue for the global climate. One way to meet this challenge is to electrochemically convert CO2 molecules to reduced carbon species such as formates, alcohols, hydrocarbons, etc., which is a difficult process due to the poor kinetics of CO2 reduction. Therefore, the use of catalysts, while preventing undesirable side reactions, can also play an important role in reducing CO2. In this study, a two-step synthesis of CuS (1, 5, 12, 24 hr) @ Cu-MOF has been reported as an advanced electrocatalyst for CO2 reduction in neutral pH environments. Bismuth has been used to improve the electrocatalytic properties of the samples. Bi-CuS... 

    Investigation of Crystallization Behavior and Electrical Properties of Glass-Ceramics in the Li2O-TiO2-P2O5 System

    , M.Sc. Thesis Sharif University of Technology Mohaghegh, Elnaz (Author) ; Nemati, Ali (Supervisor) ; Eftekhari Yekta, Bijan (Supervisor) ; Banijamali, Sara (Co-Advisor)
    Abstract
    During the past two decades, much attention has been paid to rechargeable lithium batteries, because they have high energy density. Glass-ceramics is a category of this material, which may be of great potential as solid electrolytes.. The object of this thesis is preparation of Li2O-TiO2-P2O5 glass, glass-ceramic and investigation their electrical behavior. Prepared Samples were investigated by Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-Visible spectroscopy and Electrochemical impedance spectroscopy (EIS). In this study LiTi2(PO4)3 crystals were crystallized in a glass with the composition 45Li2O-25TiO2-30P2O5 (molar ratio). According... 

    Probing the Electrochemical Properties of Gold Electrode Modified with Edge-Functionalized Graphene and its Application

    , M.Sc. Thesis Sharif University of Technology Aghajani, Talin (Author) ; Shahrokhian, Saeed (Supervisor)
    Abstract
    In the present work, edge-functionalaized graphene was used as electrode material and its electrochemical properties were systematically characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Two methods were applied to modify the gold electrode surface. First method was the self assembling process of graphene nanosheets on gold electrode surface. Second method was simply casting specific amounts of graphene suspension on the gold electrode surface. Nyquist plots show decrease of the charge transfer resistance on the electrode surface at both cases. In cyclic voltammetry studies, first electrode shows no significant changes while the second electrode exhibits... 

    Electrochemical and Photocatalytic Behaviour of V&S Doped Titania Produced with Plasma Electrolytic Oxidation

    , M.Sc. Thesis Sharif University of Technology Ahmadzadeh, Mohammad (Author) ; Ghorbani, Mohammad (Supervisor)
    Abstract
    Plasma Electrolytic Oxidation is a new and promising method for synthesis of oxide layers and coatings on light metals such as titanium and aluminum. This method is a fast, easy and economicalway to produce TiO2 layers on Ti substrate. Photocatalytic properties of TiO2 can be improved with doping of other elements such as metals and non-metals by expanding its band gap which is in UV area of light spectrum in to visible area.Photocatalytic properties of TiO2 is also dependent on surface area and grain size, oxide layers which has been produced with PEO process has a high surface area due to its porosity. Voltage, electrolyte and additives concentration are among parameters which can affect... 

    Probing the Performance of Safflower Plant as a Green Inhibitor with Molybdenum Disulfide on Corrosion Protection Properties of the Epoxy Coating

    , M.Sc. Thesis Sharif University of Technology Nematian, Bahram (Author) ; Ramazani Saadat Abadi, Ahmad (Supervisor) ; Mahdavian Ahadi, Mohammad (Supervisor)
    Abstract
    Today, the process of corrosion and compensation of minor injuries, without the need for tracing or any other physical interference, has become one of the subjects of interest to researchers. Inhibitors have been considered as one of the anti-corrosion agents. In this research, safflower extract as a green inhibitor in sodium chloride corrosive environment was used to evaluate the rate of corrosion of mild steel. Also the MoS2 nanoparticles were used as carrier of this green inhibitore in the epoxy coating to allow the activation of the coating in a scratched state in sodium chloride solution of 3.5%. In the first step, the extract of the safflower was prepared to reach the best part of this... 

    Study of Microstructural Changes Associated with Internal Resistance of a Li-ion Battery

    , M.Sc. Thesis Sharif University of Technology Tabean, Saba (Author) ; Asgari, Sirous (Supervisor)
    Abstract
    As one of the main features of Li-Ion batteries, internal resistance severely affects performance and characteristics of these batteries e.g. output power and working voltage. In this study, we tried to understand role of internal resistance on microstructure development and provide a correlative relation between microstructural features and performance of lithium-ion batteries. To catch this target, four types of Li-Ion battery chose, varying cathode type. These batteries were exposed to both normal and severe cycling conditions. Regarding to the key role of current rate on the performance of Li-ion batteries, an extensive research on different types of batteries at various current rates... 

    ZnO nanoparticle/nanorod-based label-free electrochemical immunoassay for rapid detection of MMP-9 biomarker

    , Article Biochemical Engineering Journal ; Volume 164 , 2020 Shabani, E ; Abdekhodaie, M. J ; Mousavi, S. A ; Taghipour, F ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)... 

    Zinc oxide/copper sulfide nanorods as a highly catalytic counter electrode material for quantum dot sensitized solar cells

    , Article RSC Advances ; Volume 6, Issue 57 , 2016 , Pages 51894-51899 ; 20462069 (ISSN) Eskandari, M ; Ghahary, R ; Shokri, M ; Ahmadi, V ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    Copper sulfide deposited ZnO nanorods (ZnO NRs/CuS) have been applied as a new counter electrode material with high electrocatalytic activity towards polysulfide electrolyte, which results in the formation of a highly efficient counter electrode for QDSSCs. It was observed from the current density-voltage (J-V) characteristics that the short-circuit current density (Jsc), power conversion efficiency (PCE), and fill factor (FF) were enhanced from 7.63 mA cm-2 to 14.48 mA cm-2, 1.59% to 4.18%, and 0.29 to 0.38, respectively, when a bare CuS counter electrode was changed to a ZnO NRs/CuS counter electrode. Electrochemical impedance spectroscopy (EIS), Tafel polarization and cyclic voltammetry... 

    Zinc-doped silica/polyaniline core/shell nanoparticles towards corrosion protection epoxy nanocomposite coatings

    , Article Composites Part B: Engineering ; Volume 212 , 2021 ; 13598368 (ISSN) Haddadi, S. A ; Mehmandar, E ; Jabari, H ; Ramazani Saadatabadi, A ; Mohammadkhani, R ; Yan, N ; Arjmand, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Commercial paints and coatings can serve as a protective barrier for metallic substrates in a corrosive environment. A considerable variety of nanostructures can be embedded in a polymeric coating to achieve both barrier and active protection. This research aims to elucidate the role of polyaniline (PANI) as an active polyelectrolyte modifier for the surface modification of mesoporous silica nanoparticles (MSNs) doped with zinc cations (Zn2+). To characterize the samples, we employed different techniques, including field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), Raman... 

    Water repellent room temperature vulcanized silicone for enhancing the long-term stability of perovskite solar cells

    , Article Solar Energy ; Volume 218 , 2021 , Pages 28-34 ; 0038092X (ISSN) Samadpour, M ; Heydari, M ; Mohammadi, M ; Parand, P ; Taghavinia, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    A key direction toward enhancing the long term and outdoor stability of the perovskite solar cells is encapsulation. As a result, a suitable encapsulation package is required to prevent moisture and oxygen penetration toward the perovskite solar cells. In this work, a low-cost commercially available bilayer structure of poly (methyl methacrylate)/ room-temperature vulcanizing silicone rubber (RTV) encapsulation package for enhancing the long term stability of the perovskite solar cells has been investigated. Encapsulated cells retained more than 80% of the initial efficiency at the environmental condition of 50% moisture, and room temperature after 1000 h, however reference cell efficiency... 

    Vertically standing Cu2O nanosheets promoted flower-like PtPd nanostructures supported on reduced graphene oxide for methanol electro-oxidation

    , Article Electrochimica Acta ; Volume 259 , 2018 , Pages 36-47 ; 00134686 (ISSN) Shahrokhian, S ; Rezaee, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    The present study reports a simple electrochemical approach to the fabrication of a new nanocomposite containing PtPd nanoflowers (NFs) promoted with two-dimensional (2D) nanosheets (NSs) structure cuprous oxide (Cu2O) supported on reduced graphene oxide (rGO) (PtPd-NFs/Cu2O-NSs/rGO). Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, and energy dispersive X-ray spectroscopy are used for characterization of the PtPd-NPs/Cu2O-NPs/rGO. SEM images showed that vertical-standing arrays of Cu2O with an edge length up to 1 μm and thickness of about 20 nm are electrodeposited on the surface of rGO film. Also, PtPd needle-like NFs with visible and... 

    Ultrasensitive detection of cancer biomarkers using conducting polymer/electrochemically reduced graphene oxide-based biosensor: Application toward BRCA1 sensing

    , Article Sensors and Actuators, B: Chemical ; Volume 266 , 2018 , Pages 160-169 ; 09254005 (ISSN) Shahrokhian, S ; Salimian, R ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Breast Cancer (BRCA) is the most common threat in women worldwide. Increasing death rate of diagnosed cases is the main leading cause of designing specific genosensors for BRCA − related cancer detection. In the present study, an ultrasensitive label − free electrochemical DNA (E − DNA) sensor based on conducting polymer/reduced graphene − oxide platform has been developed for the detection of BRCA1 gene. An electrochemical method was applied as a simple and controllable technique for the electrochemical reduction of graphene oxide and also, electro − polymerization of pyrrole − 3 − carboxylic acid monomer. The results of the present work show that the polymer − coated reduced graphene −...