Estudo da eficiência e estabilidade fotocatalítica de filmes de TiO2 e TiO2/TiO2-x
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Data
2022-02-22
Autores
Escaliante, Lucas Caniati
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O dióxido de titânio, TiO2, é um semicondutor usado em diferentes tipos de aplicação, tais como em sensores de gás, células solares e especialmente em fotocatálise, objeto de estudo deste trabalho. Sendo este material amplamente utilizado para aplicações fotocatalíticas, filmes de TiO2 depositados por RF sputtering reativo foram submetidos a testes de fotocatálise e avaliados. Com o objetivo de avaliar a estabilidade da atividade fotocatalítica, um primeiro com conjunto de filmes de TiO2 foi escolhido. Os filmes correspondentes foram submetidos a 16 ciclos de fotocatálise, totalizando-se mais de 100 horas de exposição. Não foram observadas perdas sistemáticas na atividade fotocatalítica dessas amostras. Esses resultados indicam que as amostras de TiO2 depositadas pela técnica de sputtering são estáveis quanto à exposição à irradiação UV em solução contendo azul de metileno. Com o intuito de promover melhoras na eficiência da atividade fotocatalítica, um segundo conjunto de filmes de TiO2 foi analisado. Amostras foram feitas sob regime de interrupção do fluxo de O2 durante as deposições por sputtering reativo. Essas interrupções duraram 10 s, 38 s, 45 s e 70 s, produzindo filmes que contém uma modulação do conteúdo de oxigênio ao longo do eixo de crescimento. Nos testes de fotocatálise, foi utilizada uma solução aquosa de azul de metileno e lâmpadas UV de vapor de mercúrio. Verificou-se uma melhora da atividade fotocatalítica em amostras desse segundo conjunto de filmes, que foram depositados sob regime de interrupções do fluxo de O2, quando comparadas com o TiO2 homogêneo, ou seja, que foi depositado sob fluxo contínuo de O2. A melhor resposta fotocatalítica foi observada na amostra correspondente a interrupções de 10 s. Os resultados mostram que a quantidade de corante degradado aumentou em média 1,67 vezes na amostra de fluxo interrompido por 10 s em comparação com o filme homogêneo de TiO2 depositado em condições semelhantes. Nesse sentido, pôde-se concluir que os filmes depositados por sputtering são quimicamente estáveis e que o procedimento de depositar os filmes sob interrupções do fluxo de O2 pode produzir melhorias significativas na atividade dos fotocatalisadores à base de TiO2.
Titanium dioxide, TiO2, is a semiconductor used in different types of applications, such as gas sensors, solar cells and especially in photocatalysis, the object of study in this work. Since this material is widely used for photocatalytic applications, TiO2 films deposited by reactive RF sputtering were subjected to photocatalysis tests and evaluated. A first set of TiO2 films was chosen and evaluated according to the stability of the photocatalytic activity and submitted to several cycles of photocatalysis. After 16 cycles of photocatalysis, totaling more than 100 hours of exposure, no systematic losses were observed in the photocatalytic activity of these samples. These results indicate that the TiO2 samples deposited by the sputtering technique are stable concerning the exposure to UV irradiation in a solution containing methylene blue dye. The second set of TiO2 films was deposited under O2 flow interruption regime during depositions by reactive sputtering. These interruptions lasted 10 s, 38 s, 45 s, and 70 s, producing films that contain a modulation of the oxygen content along the growth axis. In the photocatalysis tests, an aqueous solution of methylene blue and UV mercury vapor lamps were used. There was an improvement in the photocatalytic activity in samples of this second set of films, which were deposited under the O2 flow interruption regime, when compared with the homogeneous TiO2, that is, which was deposited under continuous O2 flow. The best photocatalytic response was observed in the sample corresponding to 10 s interruptions. The results show that the amount of degraded dye increased by an average of 1.67 times in the flow interrupted sample for 10 s compared to the homogeneous TiO2 film deposited under similar conditions. In this sense, it was concluded that the films deposited by sputtering are chemically stable and that the simple procedure of depositing the films under O2 interruptions flow can produce significant improvements in the photocatalytic activity of the TiO2-based photocatalysts.
Titanium dioxide, TiO2, is a semiconductor used in different types of applications, such as gas sensors, solar cells and especially in photocatalysis, the object of study in this work. Since this material is widely used for photocatalytic applications, TiO2 films deposited by reactive RF sputtering were subjected to photocatalysis tests and evaluated. A first set of TiO2 films was chosen and evaluated according to the stability of the photocatalytic activity and submitted to several cycles of photocatalysis. After 16 cycles of photocatalysis, totaling more than 100 hours of exposure, no systematic losses were observed in the photocatalytic activity of these samples. These results indicate that the TiO2 samples deposited by the sputtering technique are stable concerning the exposure to UV irradiation in a solution containing methylene blue dye. The second set of TiO2 films was deposited under O2 flow interruption regime during depositions by reactive sputtering. These interruptions lasted 10 s, 38 s, 45 s, and 70 s, producing films that contain a modulation of the oxygen content along the growth axis. In the photocatalysis tests, an aqueous solution of methylene blue and UV mercury vapor lamps were used. There was an improvement in the photocatalytic activity in samples of this second set of films, which were deposited under the O2 flow interruption regime, when compared with the homogeneous TiO2, that is, which was deposited under continuous O2 flow. The best photocatalytic response was observed in the sample corresponding to 10 s interruptions. The results show that the amount of degraded dye increased by an average of 1.67 times in the flow interrupted sample for 10 s compared to the homogeneous TiO2 film deposited under similar conditions. In this sense, it was concluded that the films deposited by sputtering are chemically stable and that the simple procedure of depositing the films under O2 interruptions flow can produce significant improvements in the photocatalytic activity of the TiO2-based photocatalysts.
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Palavras-chave
Fotocatálise, Estabilidade, Sputtering, Fluxo de O2, Filmes finos, Deposição química de vapor, Dióxido de titânio, Photocatalysis, Stability, Sputtering, Thin films, O2 flow