Development of Hematite-based photoanodes
Autor(a) principal: | |
---|---|
Data de Publicação: | 2023 |
Tipo de documento: | Tese |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFSCAR |
Texto Completo: | https://repositorio.ufscar.br/handle/ufscar/17990 |
Resumo: | Hydrogen production via Water Splitting has been considered one of the best solutions for energy shortages and environmental pollution. The use of hematite (α-Fe2O3) as a photoanode in photoelectrochemical hydrogen production processes has been increasingly studied due to its high stability, non-toxicity, absorption in the region up to 600 nm (covering up to 40% of the solar energy spectrum), low bandgap values (between 1.9 - 2.2 eV), high accessibility and low cost, considering that iron is the fourth most abundant element in the Earth's crust. Current density studies show that hematite has a photocurrent of 12.6 mA cm-2 under solar irradiation, reaching 16% efficiency in photoelectrochemical processes in water separation. However, it has some limitations in its effectiveness due to low electronic mobility, low electrical conductivity, between 10-14 - 10-6 Ω-1cm-1, high surface state density, and slow reaction kinetics. Among the methods used for processing the hematite photoanode, we can highlight the thin films from the colloidal deposition of magnetic nanoparticles. This technique leads to the production of high-performance hematite photoanode. However, little is known about the influence of the magnetic field and heat treatment parameters on the final properties of hematite photoanodes. Thus, the first part of the work evaluated how these processing parameters in the morphology and photoelectrochemical properties of nanostructured hematite anodes. The thickness analysis demonstrated a relationship between the magnetic field and the concentration of nanoparticles used to prepare the thin films, showing that larger magnetic fields decrease the thickness. Jabs's results corroborate the existence of the influence of the magnetic field since the use of a larger magnetic field decreases the amount of deposited material, consequently decreasing the optical absorption of thin films. PEC measurements showed that at higher concentrations, using higher magnetic fields increases JPH values, and lower magnetic fields cause a decrease in JPH when using higher concentrations of nanoparticles. Even controlling the thickness and morphology of the iron oxide-based films, the pure material has a high recombination of photogenerated charge due to its low charge separation efficiency, which can generate poor electronic transport, which has hindered its commercial application. Based on the limitations of hematite, the second part of the study was to study germanium as a potentially ideal element that combines improved charge transfer efficiency and morphology control for high-performance hematite-based photoanode. Intensity-modulated photocurrent spectroscopy (IMPS) results demonstrated that the addition of Ge increased charge mobility, leading to superior charge separation efficiency compared to pure hematite photoanode. C-AFM (Conductive Atomic Force Electron Microscopy) measurements demonstrate that Ge improves electron conductivity and increases majority carrier mobility. Photoelectrochemical measurements performed at different wavelengths show that Ge interferes with the formation of small polarons, making the charges more mobile (delocalized), thus favoring the separation process of photoinduced charges. The synergistic role played by the addition of Ge resulted in a significant improvement in photoelectrochemical performance from 0.5 to 3.2 mA cm-2 at 1.23 VRHE, comparing original and Ge-hematite-based photoanodes, respectively. |
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Rodrigues, Murillo Henrique de MatosLeite, Edson Robertohttp://lattes.cnpq.br/1025598529469393http://lattes.cnpq.br/1943658157367342https://orcid.org/0000-0001-8445-6256https://orcid.org/0000-0002-0513-9939c145ef1d-48b2-4faf-9e46-82aed1020e512023-05-10T12:11:43Z2023-05-10T12:11:43Z2023-02-17RODRIGUES, Murillo Henrique de Matos. Development of Hematite-based photoanodes. 2023. Tese (Doutorado em Química) – Universidade Federal de São Carlos, São Carlos, 2023. Disponível em: https://repositorio.ufscar.br/handle/ufscar/17990.https://repositorio.ufscar.br/handle/ufscar/17990Hydrogen production via Water Splitting has been considered one of the best solutions for energy shortages and environmental pollution. The use of hematite (α-Fe2O3) as a photoanode in photoelectrochemical hydrogen production processes has been increasingly studied due to its high stability, non-toxicity, absorption in the region up to 600 nm (covering up to 40% of the solar energy spectrum), low bandgap values (between 1.9 - 2.2 eV), high accessibility and low cost, considering that iron is the fourth most abundant element in the Earth's crust. Current density studies show that hematite has a photocurrent of 12.6 mA cm-2 under solar irradiation, reaching 16% efficiency in photoelectrochemical processes in water separation. However, it has some limitations in its effectiveness due to low electronic mobility, low electrical conductivity, between 10-14 - 10-6 Ω-1cm-1, high surface state density, and slow reaction kinetics. Among the methods used for processing the hematite photoanode, we can highlight the thin films from the colloidal deposition of magnetic nanoparticles. This technique leads to the production of high-performance hematite photoanode. However, little is known about the influence of the magnetic field and heat treatment parameters on the final properties of hematite photoanodes. Thus, the first part of the work evaluated how these processing parameters in the morphology and photoelectrochemical properties of nanostructured hematite anodes. The thickness analysis demonstrated a relationship between the magnetic field and the concentration of nanoparticles used to prepare the thin films, showing that larger magnetic fields decrease the thickness. Jabs's results corroborate the existence of the influence of the magnetic field since the use of a larger magnetic field decreases the amount of deposited material, consequently decreasing the optical absorption of thin films. PEC measurements showed that at higher concentrations, using higher magnetic fields increases JPH values, and lower magnetic fields cause a decrease in JPH when using higher concentrations of nanoparticles. Even controlling the thickness and morphology of the iron oxide-based films, the pure material has a high recombination of photogenerated charge due to its low charge separation efficiency, which can generate poor electronic transport, which has hindered its commercial application. Based on the limitations of hematite, the second part of the study was to study germanium as a potentially ideal element that combines improved charge transfer efficiency and morphology control for high-performance hematite-based photoanode. Intensity-modulated photocurrent spectroscopy (IMPS) results demonstrated that the addition of Ge increased charge mobility, leading to superior charge separation efficiency compared to pure hematite photoanode. C-AFM (Conductive Atomic Force Electron Microscopy) measurements demonstrate that Ge improves electron conductivity and increases majority carrier mobility. Photoelectrochemical measurements performed at different wavelengths show that Ge interferes with the formation of small polarons, making the charges more mobile (delocalized), thus favoring the separation process of photoinduced charges. The synergistic role played by the addition of Ge resulted in a significant improvement in photoelectrochemical performance from 0.5 to 3.2 mA cm-2 at 1.23 VRHE, comparing original and Ge-hematite-based photoanodes, respectively.A produção de hidrogênio via Water Splitting tem sido considerada uma das melhores soluções para a escassez de energia e poluição ambiental. A utilização da hematita (α-Fe2O3) como fotoanodo em processos fotoeletroquímicos de produção de hidrogênio tem sido cada vez mais estudada devido a sua alta estabilidade, não toxicidade, absorção na região de até 600 nm (abrangendo até 40% do espectro de energia solar), baixos valores de bandgap (entre 1,9 - 2,2 eV), alta acessibilidade e baixo custo, considerando que o ferro é o quarto elemento mais abundante na crosta terrestre. Estudos atuais de densidade mostram que a hematita possui uma fotocorrente de 12,6 mA cm-2 sob irradiação solar, atingindo 16% de eficiência em processos fotoeletroquímicos na separação de água. No entanto, apresenta algumas limitações em sua eficácia devido à baixa mobilidade eletrônica, baixa condutividade elétrica, entre 10-14 - 10-6 Ω-1cm-1, alta densidade de estado de superfície e cinética de reação lenta. Dentre os métodos utilizados para o processamento do fotoânodo de hematita, podemos destacar os filmes finos provenientes da deposição coloidal de nanopartículas magnéticas. Esta técnica leva à produção de fotoânodo de hematita de alto desempenho. No entanto, pouco se sabe sobre a influência do campo magnético e dos parâmetros de tratamento térmico nas propriedades finais dos fotoanodos de hematita. Assim, a primeira parte do trabalho avaliou como esses parâmetros de processamento na morfologia e nas propriedades fotoeletroquímicas de ânodos de hematita nanoestruturados. A análise de espessura demonstrou uma relação entre o campo magnético e a concentração de nanopartículas utilizadas para preparar os filmes finos, mostrando que campos magnéticos maiores diminuem a espessura. Os resultados de Jabs corroboram a existência da influência do campo magnético, pois a utilização de um campo magnético maior diminui a quantidade de material depositado, diminuindo consequentemente a absorção óptica dos filmes finos. As medições de PEC mostraram que em concentrações mais altas, o uso de campos magnéticos mais altos aumenta os valores de JPH, e campos magnéticos mais baixos causam uma diminuição no JPH ao usar concentrações mais altas de nanopartículas. Mesmo controlando a espessura e morfologia dos filmes à base de óxido de ferro, o material puro possui alta recombinação de carga fotogerada devido a sua baixa eficiência de separação de carga, o que pode gerar transporte eletrônico ruim, o que tem dificultado sua aplicação comercial. Com base nas limitações da hematita, a segunda parte do estudo foi estudar o germânio como um elemento potencialmente ideal que combina eficiência de transferência de carga aprimorada e controle de morfologia para fotoânodo de alto desempenho à base de hematita. Os resultados da espectroscopia de fotocorrente de intensidade modulada (IMPS) demonstraram que a adição de Ge aumentou a mobilidade da carga, levando a uma eficiência de separação de carga superior em comparação com o fotoânodo de hematita puro. As medições C-AFM (Microscopia eletrônica de força atômica condutiva) demonstram que o Ge melhora a condutividade eletrônica e aumenta a mobilidade dos portadores majoritários. Medidas fotoeletroquímicas realizadas em diferentes comprimentos de onda mostram que o Ge interfere na formação de pequenos polarons, tornando as cargas mais móveis (deslocalizadas), favorecendo assim o processo de separação das cargas fotoinduzidas. O papel sinérgico desempenhado pela adição de Ge resultou em uma melhora significativa no desempenho fotoeletroquímico de 0,5 para 3,2 mA cm-2 a 1,23 VRHE, comparando fotoanodos originais e baseados em Ge-hematita, respectivamente.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)engUniversidade Federal de São CarlosCâmpus São CarlosPrograma de Pós-Graduação em Química - PPGQUFSCarAttribution-NonCommercial-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nc-nd/3.0/br/info:eu-repo/semantics/openAccessHematitePhotoanodeWater-SplittingPhotocurrent densityGermaniumCND processCIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICADevelopment of Hematite-based photoanodesDesenvolvimento de fotoanodos a base de hematitainfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesis6006009c25e6a7-a2cd-4058-97ed-441bc2793123reponame:Repositório Institucional da UFSCARinstname:Universidade Federal de São Carlos (UFSCAR)instacron:UFSCARCC-LICENSElicense_rdflicense_rdfapplication/rdf+xml; charset=utf-8810https://repositorio.ufscar.br/bitstream/ufscar/17990/4/license_rdff337d95da1fce0a22c77480e5e9a7aecMD54ORIGINALTese Doutorado - Rodrigues MHM.pdfTese Doutorado - Rodrigues MHM.pdfapplication/pdf5544885https://repositorio.ufscar.br/bitstream/ufscar/17990/3/Tese%20Doutorado%20-%20Rodrigues%20MHM.pdf38fb60f555a79c8ae02def433900f770MD53TEXTTese Doutorado - Rodrigues MHM.pdf.txtTese Doutorado - Rodrigues MHM.pdf.txtExtracted texttext/plain172054https://repositorio.ufscar.br/bitstream/ufscar/17990/5/Tese%20Doutorado%20-%20Rodrigues%20MHM.pdf.txt8f15f9e002a92c0d16a73852f285d086MD55THUMBNAILTese Doutorado - Rodrigues MHM.pdf.jpgTese Doutorado - Rodrigues MHM.pdf.jpgIM Thumbnailimage/jpeg7633https://repositorio.ufscar.br/bitstream/ufscar/17990/6/Tese%20Doutorado%20-%20Rodrigues%20MHM.pdf.jpgb037d36fde32c07b21e513e3f0ca8d61MD56ufscar/179902023-09-18 18:32:38.571oai:repositorio.ufscar.br:ufscar/17990Repositório InstitucionalPUBhttps://repositorio.ufscar.br/oai/requestopendoar:43222023-09-18T18:32:38Repositório Institucional da UFSCAR - Universidade Federal de São Carlos (UFSCAR)false |
dc.title.eng.fl_str_mv |
Development of Hematite-based photoanodes |
dc.title.alternative.por.fl_str_mv |
Desenvolvimento de fotoanodos a base de hematita |
title |
Development of Hematite-based photoanodes |
spellingShingle |
Development of Hematite-based photoanodes Rodrigues, Murillo Henrique de Matos Hematite Photoanode Water-Splitting Photocurrent density Germanium CND process CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
title_short |
Development of Hematite-based photoanodes |
title_full |
Development of Hematite-based photoanodes |
title_fullStr |
Development of Hematite-based photoanodes |
title_full_unstemmed |
Development of Hematite-based photoanodes |
title_sort |
Development of Hematite-based photoanodes |
author |
Rodrigues, Murillo Henrique de Matos |
author_facet |
Rodrigues, Murillo Henrique de Matos |
author_role |
author |
dc.contributor.authorlattes.por.fl_str_mv |
http://lattes.cnpq.br/1943658157367342 |
dc.contributor.authororcid.por.fl_str_mv |
https://orcid.org/0000-0001-8445-6256 |
dc.contributor.advisor1orcid.por.fl_str_mv |
https://orcid.org/0000-0002-0513-9939 |
dc.contributor.author.fl_str_mv |
Rodrigues, Murillo Henrique de Matos |
dc.contributor.advisor1.fl_str_mv |
Leite, Edson Roberto |
dc.contributor.advisor1Lattes.fl_str_mv |
http://lattes.cnpq.br/1025598529469393 |
dc.contributor.authorID.fl_str_mv |
c145ef1d-48b2-4faf-9e46-82aed1020e51 |
contributor_str_mv |
Leite, Edson Roberto |
dc.subject.eng.fl_str_mv |
Hematite Photoanode Water-Splitting Photocurrent density Germanium CND process |
topic |
Hematite Photoanode Water-Splitting Photocurrent density Germanium CND process CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
dc.subject.cnpq.fl_str_mv |
CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA |
description |
Hydrogen production via Water Splitting has been considered one of the best solutions for energy shortages and environmental pollution. The use of hematite (α-Fe2O3) as a photoanode in photoelectrochemical hydrogen production processes has been increasingly studied due to its high stability, non-toxicity, absorption in the region up to 600 nm (covering up to 40% of the solar energy spectrum), low bandgap values (between 1.9 - 2.2 eV), high accessibility and low cost, considering that iron is the fourth most abundant element in the Earth's crust. Current density studies show that hematite has a photocurrent of 12.6 mA cm-2 under solar irradiation, reaching 16% efficiency in photoelectrochemical processes in water separation. However, it has some limitations in its effectiveness due to low electronic mobility, low electrical conductivity, between 10-14 - 10-6 Ω-1cm-1, high surface state density, and slow reaction kinetics. Among the methods used for processing the hematite photoanode, we can highlight the thin films from the colloidal deposition of magnetic nanoparticles. This technique leads to the production of high-performance hematite photoanode. However, little is known about the influence of the magnetic field and heat treatment parameters on the final properties of hematite photoanodes. Thus, the first part of the work evaluated how these processing parameters in the morphology and photoelectrochemical properties of nanostructured hematite anodes. The thickness analysis demonstrated a relationship between the magnetic field and the concentration of nanoparticles used to prepare the thin films, showing that larger magnetic fields decrease the thickness. Jabs's results corroborate the existence of the influence of the magnetic field since the use of a larger magnetic field decreases the amount of deposited material, consequently decreasing the optical absorption of thin films. PEC measurements showed that at higher concentrations, using higher magnetic fields increases JPH values, and lower magnetic fields cause a decrease in JPH when using higher concentrations of nanoparticles. Even controlling the thickness and morphology of the iron oxide-based films, the pure material has a high recombination of photogenerated charge due to its low charge separation efficiency, which can generate poor electronic transport, which has hindered its commercial application. Based on the limitations of hematite, the second part of the study was to study germanium as a potentially ideal element that combines improved charge transfer efficiency and morphology control for high-performance hematite-based photoanode. Intensity-modulated photocurrent spectroscopy (IMPS) results demonstrated that the addition of Ge increased charge mobility, leading to superior charge separation efficiency compared to pure hematite photoanode. C-AFM (Conductive Atomic Force Electron Microscopy) measurements demonstrate that Ge improves electron conductivity and increases majority carrier mobility. Photoelectrochemical measurements performed at different wavelengths show that Ge interferes with the formation of small polarons, making the charges more mobile (delocalized), thus favoring the separation process of photoinduced charges. The synergistic role played by the addition of Ge resulted in a significant improvement in photoelectrochemical performance from 0.5 to 3.2 mA cm-2 at 1.23 VRHE, comparing original and Ge-hematite-based photoanodes, respectively. |
publishDate |
2023 |
dc.date.accessioned.fl_str_mv |
2023-05-10T12:11:43Z |
dc.date.available.fl_str_mv |
2023-05-10T12:11:43Z |
dc.date.issued.fl_str_mv |
2023-02-17 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
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info:eu-repo/semantics/doctoralThesis |
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doctoralThesis |
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dc.identifier.citation.fl_str_mv |
RODRIGUES, Murillo Henrique de Matos. Development of Hematite-based photoanodes. 2023. Tese (Doutorado em Química) – Universidade Federal de São Carlos, São Carlos, 2023. Disponível em: https://repositorio.ufscar.br/handle/ufscar/17990. |
dc.identifier.uri.fl_str_mv |
https://repositorio.ufscar.br/handle/ufscar/17990 |
identifier_str_mv |
RODRIGUES, Murillo Henrique de Matos. Development of Hematite-based photoanodes. 2023. Tese (Doutorado em Química) – Universidade Federal de São Carlos, São Carlos, 2023. Disponível em: https://repositorio.ufscar.br/handle/ufscar/17990. |
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https://repositorio.ufscar.br/handle/ufscar/17990 |
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eng |
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eng |
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600 600 |
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Attribution-NonCommercial-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nc-nd/3.0/br/ info:eu-repo/semantics/openAccess |
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Attribution-NonCommercial-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nc-nd/3.0/br/ |
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openAccess |
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Universidade Federal de São Carlos Câmpus São Carlos |
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Programa de Pós-Graduação em Química - PPGQ |
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UFSCar |
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Universidade Federal de São Carlos Câmpus São Carlos |
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