| Titre : | Synthesis and physicochemical properties of oxides based on lanthanum and transitions metals |
| Auteurs : | Fawzi Hadji, Auteur ; Mourad Mebarki, Directeur de thèse ; Mahmoud Omari, Directeur de thèse |
| Type de document : | Thése doctorat |
| Editeur : | Biskra [Algérie] : Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Mohamed Khider, 2023 |
| Format : | 1 vol. (115 p.) / ill., couv. ill. en coul / 30 cm |
| Langues: | Anglais |
| Langues originales: | Anglais |
| Résumé : |
Developing economical and highly efficient electrode material is crucial for water electrolysis and supercapacitors associated with energy conversion and storage. For this purpose, we successfully elaborated a new series of LaCo1 xZnxO3 oxides (x = 0, 0.03, 0.05, 0.1, 0.2, 0.3 and 0.4) via a facile sol gel route. We investigated, for the first time, their structural, morphological and electrochemical properties for possible use as electrode material toward oxygen evolution reaction and supercapacitor in a basic solution. Among the developed materials, the LaCo0.9Zn0.1O3 electrocatalyst displays a remarkable performance; an overpotential of merely 327 mV is needed to generate a specified current density of 10 mA.cm 2geo; a current density of around 73.41 mA.cm−2 at 450 mV, almost twice as high compared to the pristine electrocatalyst; a faster reaction kinetic with a lower Tafel slope of ~92 mV.dec−1 and an activity loss of less than 4 % after 24 hours of utilization. On the other hand, the LaCo0.95Zn0.05O3 electrode provides the best specific capacitance (300.47 F/g); this is almost four times higher compared to the undoped electrode (75.36 F/g). The electrode material also shows excellent capacitance retention of 85.73% after 5000 cycles at 5 A/g. In addition, a hybrid supercapacitor with high energy density was constructed by combining LaCo0.95Zn0.05O3 with activated carbon. The LaCo0.95Zn0.05O3//activated carbon hybrid device offers a high energy density of 36.12 Wh.kg 1 at a power density of 390.35 W.kg 1. The device is characterized by outstanding retention of the capacitance of 81% after being subjected to 5000 successive charge discharge cycles. |
| Sommaire : |
1. Introduction……………………………………………………………………………….1 1.1. Hypothesis/Problem Statement………………………………………………………...2 1.2. Objectives and Scope………………………………….……………………………….5 1.3. Dissertation Overview…………………………………………………………………5 References…………………………………………………………………………………….7 Chapter I: Literature Review I.1. Generalities on mixed oxides…………………………………………………………….9 I.2. Perovskite structure…………...………………………………………………………....9 I.2.1 The crystal structure………………….…………………………………………………10 I.2.2. Valence of A and B cations…………………...…...……………………………………10 I.2.3. Stability of the structure………………………………………………………………...11 I.2.4. Defects in the crystals…………….…………………………………………………….14 I.2.5. Mechanism of defect diffusion………………………………………………………....16 I.2.6. Properties of perovskite type material…………………………………………………17 I.3. Applications…………………………………………………………...…………………17 I.3.1. Water electrolysis………………………………………………………………………18 I.3.1.1. Brief historical overview………………………………………………………...…...18 I.3.1.2. Fundamental principles………………………………………………………………19 I.3.1.3. Low--temperature electrolysis………………………………………………………...20 I.3.1.3.1. Acidic electrolysis………………………………………………………………….20 I.3.1.3.2. Alkaline electrolysis…………………………………………………………...…...21 I.3.1.4. Electrochemical reactions in water electrolysis………………………………………23 I.3.1.5. Applications of green hydrogen……………………………………………………...28 I.3.2. Electrochemical supercapacitor (ESC)………………………………………………29 I.3.2.1. Brief historical overview………………………………………………………...…...29 I.3.2.2. Fundamental principles………………………………………………………………32 I.3.2.2.1. Current collectors……………………………………………………………...…...32 I.3.2.2.2. Separator……………………………………………………………………………33 I.3.2.2.3. Electrolyte………………………………………………………………………….34 I.3.2.2.4. Electrode material………………………………………………………………….35 I.3.2.3. Energy storage mechanism……………………………………………………...…...38 I.3.2.3.1. Electrochemical double layer capacity (EDLC)…………………………………...38 I.3.2.3.2. Pseudo--capacity…………………………………………………………………...39 I.3.2.3.3. Battery--like behavior………………………………………………………….......41 I.3.2.4. Classifications of ESC………………………………………………………………43 I.3.2.5. Applications of ESC………………………………………………………………...45 References…………………………………………………………………………………..47 Chapter II: Synthesis and Characterization Techniques II.1. Synthesis Method……………………………………………………………………...56 II.1.1. Sol--gel method………………………………………………………………………...56 II.1.2. Principle……………………………………………………………………………….57 II.1.3. Factors influencing the reaction mechanisms…………………………………………60 II.1.4. Sol--gel process advantages and disadvantages…………………………………...…...61 II.2. Physico--chemical characterizations………………………….....................................62 II.2.1. Differential thermal analysis and thermo--gravimetric (DTA--TG) ……………….…...62 II.2.2. X--ray diffraction (XRD)………………………………………………………….…...62 II.2.3. Fourier transform infrared spectroscopy (FT--IR) ………………………………...….64 II.2.4. X--ray photoelectron spectroscopy (XPS)…………………………………………….65 II.2.5. Scanning electron microscopy (SEM)…………………………………………...…...67 II.2.6. Energy--dispersive X--ray spectroscopy (EDS)………………………………..............68 II.2.7. Laser particle size….........................................69 II.2.8. Nitrogen adsorption--desorption……………………………………………………....70 II.3. Electrochemical measurements……………………………………………………...73 II.3.1. Experimental apparatus…………………………………………………………........73 II.3.2. Experimental techniques………………………………………………………...…...74 II.3.2.1. Linear Sweep Voltammetry (LSV)………………………………………………...74 II.3.2.2. Electrochemical Impedance Spectroscopy (EIS)………………………………….76 II.3.2.3. Chronopotentiometry (CP)………………………………………………………...77 II.3.2.4. Cyclic voltammetry (CV)…………………………………………………………...78 II.3.2.5. Galvanostatic charge and discharge (GCD)………………………………………...80 References……………………………………………………………………………………83 Chapter III: Synthesis and electrocatalytic properties of zinc doping lanthanum cobaltite perovskite as an electrocatalyst for the oxygen evolution reaction III.1. Introduction…………………………………………………………………......…...87 III.2. Experimental…………………………………………………………………………89 III.2.1. Elaboration of LCZ electrocatalysts………………………………………………….89 III.2.2. Electrodes preparation…………………………………………………………...…...90 III.3. Results and discussion……………………………………………………………….92 III.3.1. Structural properties………………………………………………………………….92 III.3.2. Morphological properties…………………………………………………………...101 III.3.3. Electrocatalytic properties……………………………………………………...…...106 Conclusions…………………………………………………………………………………113 References……………………………………………………………………………...…...115 |
| Type de document : | Thése doctorat |
| En ligne : | http://thesis.univ-biskra.dz/id/eprint/6321 |
Disponibilité (1)
| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TCH/107 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
