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Nano-Materials Employment in Energy Harvesting and Storage Devices Politecnico di Torino Porto Institutional Repository [Doctoral thesis] Nano-materials employment in energy harvesting and storage devices Original Citation: Dimitrios Tamvakos (2015). Nano-materials employment in energy harvesting and storage devices. PhD thesis Availability: This version is available at : http://porto.polito.it/2598393/ since: March 2015 Published version: DOI:10.6092/polito/porto/2598393 Terms of use: This article is made available under terms and conditions applicable to Open Access Policy Arti- cle ("Creative Commons: Attribution 3.0") , as described at http://porto.polito.it/terms_and_ conditions.html Porto, the institutional repository of the Politecnico di Torino, is provided by the University Library and the IT-Services. The aim is to enable open access to all the world. Please share with us how this access benefits you. Your story matters. (Article begins on next page) POLITECNICO DI TORINO DEPARTMENT OF APPLIED SCIENCES AND TECHNOLOGY Doctorate in electronic devices (ciclo XXVII) Nano-materials employment in energy harvesting and storage devices. Scientific supervisor: Dr. Daniele Pullini (Fiat research centre) Academic advisor: Prof. Giancarlo Cicero (Politecnico di Torino) Candidate: Dimitrios Tamvakos ii Contents List of Figures vii List of Tables xi Abstact…..................................................................................................................................................................1 Chapter 1 ..................................................................................................................................................................4 Energy harvesting and storage, background and motivation ..................................................................................4 1.1 Energy production and use .......................................................................................................................4 1.2 ZnO in mechanical energy harvesting ............................................................................................................5 1.3 Piezoelectric effect and ZnO ...........................................................................................................................7 1.4 Electrical energy storage ................................................................................................................................8 1.5 Supercapacitors ........................................................................................................................................... 10 1.6 Types of supercapacitors ............................................................................................................................. 12 1.6.1 Electric Double-Layer Capacitors (EDLC) .............................................................................................. 12 1.6.2 Pseudo-capacitors ................................................................................................................................ 13 1.6.3 Asymmetric or hybrid capacitors .......................................................................................................... 14 1.7 Conclusion ................................................................................................................................................... 15 Chapter 2 ............................................................................................................................................................... 18 ZnO nanostructures for mechanical energy harvesting ........................................................................................ 18 2.1 Zinc Oxide nano-structures ......................................................................................................................... 18 2.2 ZnO Thin films by RF magnetron sputtering ................................................................................................ 20 2.3 ZnO (1D) Nanowires by Electrochemical deposition ................................................................................... 26 2.3.1 ECD ZnO Nanorods in free standing mode ........................................................................................... 29 2.3.2 ZnO Nanowires in porous templates .................................................................................................... 39 2.4 ZnO Nanowires by Hydrothermal growth ................................................................................................... 47 2.4.1 Zinc acetate dihydrate seed layer in hydrothermal growth ................................................................. 48 2.4.2 Zinc oxide thin film as seed layer in hydrothermal growth .................................................................. 49 Chapter 3 ............................................................................................................................................................... 54 Piezoelectric response and energy harvesting performance of ZnO nanostructures ........................................... 54 iii 3.1 Piezoresponse force microscopy. .......................................................................................................... 54 3.2 PFM measurements on ECD ZnO nanorods. ......................................................................................... 55 3.2.1 PFM measuring process ................................................................................................................. 57 3.2.2 PFM results .................................................................................................................................... 58 3.3 Energy harvesting ........................................................................................................................................ 62 3.3.1 Device fabrication ................................................................................................................................. 62 3.3.2 Piezoelectric tests on ZnO NRs grown electrochemically on rigid substrates ...................................... 64 3.3.3 Piezoelectric tests on ZnO NWs grown hydrothermally on flexible substrates ................................... 70 Chapter 4 ............................................................................................................................................................... 80 Graphene based materials in supercapacitor electrodes ..................................................................................... 80 4.1 Electrode materials ...................................................................................................................................... 80 4.1.1 Activated Carbon .................................................................................................................................. 81 4.1.2 Carbon Nanotubes (CNT) ...................................................................................................................... 82 4.1.3 Graphene .............................................................................................................................................. 83 4.2 Properties and characterization of Graphene based materials .................................................................. 84 4.2.1 Commercially available Graphene nano-platelets (GNPs) ................................................................... 84 4.2.2 Functionalized Graphene nano-platelets with MnO2 ........................................................................... 87 4.2.3 Electrochemically exfoliated Graphene nano-platelets (eGNP) from graphite ................................... 89 4.2.4 Chemically reduced graphene oxide (rGO) .......................................................................................... 92 Chapter 5 ............................................................................................................................................................. 100 Electrochemical characterization of supercapacitor devices .............................................................................. 100 5.1 Measurements cell .................................................................................................................................... 100 5.2 Electrochemical measurements ................................................................................................................ 103 5.2.1 Capacitance performance by Cyclic Voltammetry (CV) ...................................................................... 103 5.2.2 Capacitance performance by Galvanostatic charge-discharge (CD) .................................................. 105 5.2.3 Energy and Power density .................................................................................................................. 106 5.3 Graphene based electrodes performance ................................................................................................. 108 5.3.1 Graphene nano-platelets .................................................................................................................... 108 5.3.2 Reduced graphene oxide rGO ............................................................................................................ 113 Conclusion ........................................................................................................................................................... 118 Bibliography ........................................................................................................................................................
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