Nano-architectures with hierarchical porosity manufactured by colloidal techniques for application in ceramic semiconductor-based supercapacitors

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dc.contributor.advisor Gordo Odériz, Elena
dc.contributor.advisor Ferrari Fernández, Begoña
dc.contributor.advisor González Granados, Zoilo Yus Domínguez, Joaquín Luis 2020-10-01T14:27:50Z 2020-10-01T14:27:50Z 2019-07 2019-09-16
dc.description Mención Internacional en el título de doctor
dc.description Esta tesis contiene artículos de investigación en anexo
dc.description.abstract All the scientific contributions presented in this thesis have a main goal: to achieve science and technology challenges in the manufacture of energy storage devices based on a ceramic semiconductor employing colloidal processing strategies. Needs of the renewable energy systems and portable devices have revolutionized research on energy storage systems. Development of more powerful devices able to store large amounts of energy is now the challenge. In this field, the research in supercapacitors (SC) based on ceramic semiconductors has been tackled as a relevant issue to improve the electrochemical response of the electrodes inducing better reactant–catalyst contacts through the design of complex structures with large surface-to-volume ratio. The structuring and electrochemical activity of the pseudocapacitors (PCs) electrodes can be controlled by tuning the physical properties of the electroactive material (particle size, crystalline phase, preferred orientation) but also, shaping and consolidating the ceramic microstructure (publication 1). As a promising electroactive material (and non-strategic raw material), the NiO presents an elevated theoretical capacitance, high thermal and chemical stability and easy availability (publication 1). For these reasons, in this research work, he ultrasound aided synthesis of Ni(OH)2 and NiO nanoplatelets was standardized, and the manufacture of tridimensional (3D) and bidimensional (2D) NiO-based electrodes for PCs was tackled throughout different colloidal processing strategies. The Electrophoretic Deposition (EPD) and inkjet printing (IJP) technologies have been employed as shaping techniques for the manufacturing of these electrodes. While EPD allows us to fully and homogeneously coating collectors with complex shapes, as 3D Ni foams, the IJP enables the miniaturization of 2D electrodes for their use in energy-storage microdevices (publication 5). Both techniques are based on the dispersion and stabilization of Ni(OH)2 and NiO nanoplatelets in colloidal water-based suspensions, which were optimized for each application, leading to PC electrodes with specific capacitances of 250 and 160 F/g with retentions of 71 and 100%, respectively, where the remarkable low charge transfer resistance (Rct = 0.23Ω) of NiO patterns (IJP) has to be highlighted. Moreover, the assembly of synthesized NiO nanoplatelets has been also addressed resulting in a cohort of semiconductor microarchitectures that improves the electrochemical response of PC electrodes shaped by EPD. EPD is a well-known colloidal technique with remarkable performance in the coating of electrodes with complex shapes. However, for PC electrodes shaping, the nature and shape of the substrate have to be considered since collector has a relevant influence on electron transfer phenomena as well as the ion diffusion at the electrode/electrolyte interface (publication 4 & 7). The deposition and consolidation of the electroactive nanoplatelets through a mild heat treatment (sintering) connects the particles by the formation of sintering necks reducing Rct of these 3D electrodes to 1.71Ω. (publication 2 & 7). To cover Ni-3D collectors improving electrochemical performance, one of the employed colloidal strategies in this thesis was the surface modification of NiO nanoplatelets by layer-by-layer deposition of polyelectrolytes, leading to the formation of organic/inorganic core-shell structures which strongly modified the NiO nanoplatelets assembly by EPD (publication 3). The resulting hierarchical nanostructure presents high Rct values (3.65 Ω), while the capacitive response (CPE-p = 0.90) step up due to the enhancement of electrolyte wetting and faster ion diffusion. This fully ceramic porous nanostructure shows a specific capacitance of 982 F/g, with 60% retention after 1000 cycles, and relaxation times in the rage of carbonaceous SC electrodes (τ0 = 18 s), demonstrating that the capacitance is strongly related to the surface exposure of the semiconductor to the electrolyte, in spite of a relative high Rct. This is because of the increase in resistance is compensated by a better capacitive behavior as well as a better rate capability (publication 7). Finally, we also demonstrate that Rct can be reduced by the inclusion of materials capable of sharing their free electrons within the semiconductor microstructure such as metallic Ni or reduced graphene Oxide (RGO) (publication 2, 6 & 7), without deteriorating the capacitive response. In this way, NiO/Ni electrodes with specific capacitances of 755 F/gr and a retention of 71% was shaped by EPD in Ni foams, leading to Rct values of 1.55Ω and relaxation times of 11 s; while RGO/NiO hybrid supercapacitors (HSC) were prepared also by EPD, exhibiting specific capacitances of 920 F/g at a current density of 2 A/g with a retention of 71% and a Rct as low as 1.13Ω and a relaxation time of 4 s.
dc.language.iso eng
dc.rights Atribución-NoComercial-SinDerivadas 3.0 España
dc.subject.other Supercapacitors
dc.subject.other Ceramic semiconductors
dc.subject.other Energy-efficient storage devices
dc.subject.other Colloidal techniques
dc.subject.other Nanotechnology
dc.title Nano-architectures with hierarchical porosity manufactured by colloidal techniques for application in ceramic semiconductor-based supercapacitors
dc.type doctoralThesis
dc.subject.eciencia Materiales
dc.rights.accessRights openAccess Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de Madrid
dc.description.responsability Presidente: María Eugenia Rabanal Jiménez.- Secretario: Jadra Mosa Ruiz.- Vocal: Sandra Cabañas Polo
dc.contributor.departamento Universidad Carlos III de Madrid. Departamento de Ciencia e Ingeniería de Materiales e Ingeniería Química
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