Biocompósitos de ZnO e biosílica da diatomácea marinha Thalassiosira pseudonana: potenciais fotoletrodos
Data
2022-08-22
Autores
Hata, Gabriel Yuji 
Orientadores
Mazzo, Tatiana Martelli
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Em 2021 foi proclamada pela ONU o início da Década da Ciência Oceânica para o Desenvolvimento Sustentável e, com isso, o desenvolvimento de materiais sustentáveis de origem marinha passa a ter um maior destaque. As microalgas, organismos fitoplanctônicos vem ganhando notoriedade devido a sua vasta gama de aplicações especialmente as diatomáceas devido o seu grande potencial para a aplicação em energia solar como um substrato cerâmico composto de nanoporos hierarquicamente ordenados e com resistência térmica e química. O presente trabalho teve como objetivo produzir um fotoeletrodo com potencial para aplicação fotovoltaica formado a partir dos compostos de biosílica extraída da Thalassiosira pseudonana (BMAK 172) e óxido de zinco, estudando os parâmetros estruturais, morfológicos e fotoeletroquímicos deste material. Para tal, foram preparados fotoeletrodos de biosílica pura, de ZnO puro e de 3 compósitos de ZnO/Biosílica em diferentes proporções (25, 50 e 75% de biosílica). Todos os materiais obtidos no presente trabalho foram caracterizados por Difração de Raio X (DRX), Microscopia Eletrônica de Alta Emissão de Campo (MEV-FEG), Espectroscopia de Infravermelho por Transformada de Fourier (ATR-FTIR), Espectroscopia de Absorção de Luz na Região do Ultravioleta-Visível (UV-Vis), Espectroscopia de Impedância Eletroquímica (EIE) e a Voltametria linear. Como resultados, constatou-se pelas técnicas de DRX, ATR-FTIR e MEV-FEG o êxito do cultivo e da extração da biosílica de alta pureza. Além disso, por meio das técnicas de DRX, ATR-FTIR, UV-Vis, MEV-FEG foi confirmada a formação química dos compósitos ZnO/Biosílica. Através da técnica de voltametria linear e o EIE, observou-se que todos os fotoeletrodos desenvolvidos no presente trabalho apresentaram densidade de corrente, sendo que o fotoeletrodo que apresentou o maior desempenho foi o do compósito ZnO/Biosílica 75 devido a formação de uma heterojunção do tipo 2 que permite a melhor separação de cargas possível assim como a menor taxa de recombinação de elétrons, indicando que através do uso de um recurso marinho sustentável e processos de cultivo/síntese ecologicamente amigáveis, fáceis e de baixo custo, obteve-se um potencial fotoeletrodo para aplicação em células fotovoltaicas.
In 2021, the UN proclaimed the beginning of the Decade of Ocean Science for Sustainable Development and, because of that, the development of sustainable marine origin materials has been getting greater prominence. Microalgae, phytoplanktonic organisms that have already gained notoriety due to their wide range of applications such as nanotechnology, human supplementation, biofuels, nanomedicine etc., have become more important for the development of these materials, linking the plurality of uses to the cultivation ease. Diatoms, microalgae with amorphous biosilicate exoskeletons [SiO2.nH20], called frustules, have great potential for application in solar energy due to their use as a ceramic substrate because of the frustules which are composed of hierarchically ordered nanopores and have a thermal and chemical resistance. The present work is aimed at analyzing the pure biosilica extracted from the marine diatom Thalassiosira pseudonana (BMAK 172) and it composite formed with zinc oxide (ZnO) in structural, morphological and photoelectrochemical aspects. For this purpose, three photoelectrodes were prepared based on pure biosilica and ZnO at different proportions (25, 50 and 75% of biosilica) were characterized by X-ray Diffraction, Field-emission Scanning Electron Microscopy (FE-SEM), Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR), Ultraviolet–visible spectroscopy (UV-Vis), Electrochemical impedance spectroscopy (EIS) and Linear Voltammetry. The result of this study demonstrated the success of bioslica cultivation and extraction process verified by X-ray diffraction and MEV-FEG. Futhermore, the chemical formation of the composites formed by ZnO and Biosilica was confirmed by DRX, ATR-FTIR, UV-Vis and MEV-FEG. The analysis by linear voltammetry and EIS indicates the zinc oxide/Biosilica 75 composite showed the highest performance due to a type-II heterojuction formation. This allows the best possible charge separation as well as the lower rate of electron recombination, indicating that through the use of a sustainable marine resource and ecologically friendly, easy and low-cost cultivation/synthesis processes, a photoelectrode potential for application in photovoltaic cells was obtained.
In 2021, the UN proclaimed the beginning of the Decade of Ocean Science for Sustainable Development and, because of that, the development of sustainable marine origin materials has been getting greater prominence. Microalgae, phytoplanktonic organisms that have already gained notoriety due to their wide range of applications such as nanotechnology, human supplementation, biofuels, nanomedicine etc., have become more important for the development of these materials, linking the plurality of uses to the cultivation ease. Diatoms, microalgae with amorphous biosilicate exoskeletons [SiO2.nH20], called frustules, have great potential for application in solar energy due to their use as a ceramic substrate because of the frustules which are composed of hierarchically ordered nanopores and have a thermal and chemical resistance. The present work is aimed at analyzing the pure biosilica extracted from the marine diatom Thalassiosira pseudonana (BMAK 172) and it composite formed with zinc oxide (ZnO) in structural, morphological and photoelectrochemical aspects. For this purpose, three photoelectrodes were prepared based on pure biosilica and ZnO at different proportions (25, 50 and 75% of biosilica) were characterized by X-ray Diffraction, Field-emission Scanning Electron Microscopy (FE-SEM), Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR), Ultraviolet–visible spectroscopy (UV-Vis), Electrochemical impedance spectroscopy (EIS) and Linear Voltammetry. The result of this study demonstrated the success of bioslica cultivation and extraction process verified by X-ray diffraction and MEV-FEG. Futhermore, the chemical formation of the composites formed by ZnO and Biosilica was confirmed by DRX, ATR-FTIR, UV-Vis and MEV-FEG. The analysis by linear voltammetry and EIS indicates the zinc oxide/Biosilica 75 composite showed the highest performance due to a type-II heterojuction formation. This allows the best possible charge separation as well as the lower rate of electron recombination, indicating that through the use of a sustainable marine resource and ecologically friendly, easy and low-cost cultivation/synthesis processes, a photoelectrode potential for application in photovoltaic cells was obtained.
Descrição
Citação
HATA, Gabriel Yuji. Biocompósitos de ZnO e biosílica da diatomácea marinha Thalassiosira pseudonana: potenciais fotoletrodos. Orientadora: Tatiana Martelli Mazzo, 2022. 116 f. Disertação (Mestrado Interdisciplinar em Ciência e Tecnologia do Mar) - Instituto do Mar, Universidade Federal de São Paulo, Santos, 2022.