Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films

Growing energy demand and the need to reduce CO₂ emissions have driven research into solar energy conversion technologies, such as water splitting by photoelectrochemical processes (PEC). In this context, niobium pentoxide (Nb₂O₅) is a promising material due to its stability and semiconducting prope...

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Detalhes bibliográficos
Autor: Alonso Muñoz, Mario
Formato: tesis de maestría
Fecha de publicación:2025
País:España
Recursos:Universidad de Cantabria (UC)
Repositorio:UCrea Repositorio Abierto de la Universidad de Cantabria
Idioma:inglés
OAI Identifier:oai:repositorio.unican.es:10902/36325
Acesso em linha:https://hdl.handle.net/10902/36325
Access Level:acceso abierto
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spelling Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin filmsAlonso Muñoz, MarioGrowing energy demand and the need to reduce CO₂ emissions have driven research into solar energy conversion technologies, such as water splitting by photoelectrochemical processes (PEC). In this context, niobium pentoxide (Nb₂O₅) is a promising material due to its stability and semiconducting properties, although its wide bandgap limits its absorption in the visible spectrum. To improve its performance, ammonolysis has been explored as a method to modify its electronic structure and enhance its photoelectrochemical response. Nb₂O₅ thin films were synthesized by dip-coating on silicon and quartz glass substrates, followed by heat treatment and ammonolysis at temperatures of 750 and 800 °C in an ammonia atmosphere. Structural characterization confirmed the formation of Nb₂O₅ with a pseudohexagonal structure, while X-ray photoelectron spectroscopy (XPS) analysis demonstrated the incorporation of nitrogen in the ammonia-treated samples. The performance of the photoelectrodes was evaluated through PEC tests under UV (500 W/m²) and visible (1000 W/m²) light illumination. On silicon substrates, films ammonolyzed at 800 °C showed a significant increase in photogenerated current under UV irradiation (~1 mA), indicating an improvement in charge separation efficiency. However, the response in the visible spectrum remained low (~100 μA), suggesting that although ammonolysis slightly reduces the bandgap, absorption is still insufficient for efficient visible light conversion. In contrast, films on quartz glass exhibited negligible photoelectrochemical activity, indicating that this substrate does not favor charge transport under the evaluated conditions. Post-PEC XPS analysis revealed that the ammonolyzed samples suffered from charging effects, indicating a loss of conductivity. The survey spectrum showed an increase in oxygen and carbon content, likely due to contamination from the electrolyte or reaction intermediates. Additionally, the emergence of more pronounced silicon peaks suggests degradation or partial detachment of the thin film during electrochemical testing. The chemical stability evaluation was hindered by these charging effects, preventing a conclusive assessment of post-PEC oxidation states and composition. In conclusion, ammonolysis at 800 °C enhances the PEC activity of Nb₂O₅ in the UV range but does not significantly improve its efficiency in the visible spectrum. Furthermore, the post-PEC analysis indicates that the thin films may degrade or detach over time under electrochemical conditions. These findings highlight the need for additional strategies, such as doping, heterostructure formation, or improved stabilization techniques, to optimize the material for long-term PEC applications.Máster en Ingeniería QuímicaDiban Gómez, NazelyWeidenkaff, AnkeUniversidad de Cantabria20252025-04-30master thesishttp://purl.org/coar/resource_type/c_bdccNAhttp://purl.org/coar/version/c_be7fb7dd8ff6fe43info:eu-repo/semantics/masterThesishttps://hdl.handle.net/10902/36325reponame:UCrea Repositorio Abierto de la Universidad de Cantabriainstname:Universidad de Cantabria (UC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2Attribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/openAccessoai:repositorio.unican.es:10902/363252026-06-02T12:39:31Z
dc.title.none.fl_str_mv Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
title Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
spellingShingle Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
Alonso Muñoz, Mario
title_short Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
title_full Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
title_fullStr Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
title_full_unstemmed Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
title_sort Synthesis and photoelectrochemical characterization of (ammonolyzed) Nb2O5 thin films
dc.creator.none.fl_str_mv Alonso Muñoz, Mario
author Alonso Muñoz, Mario
author_facet Alonso Muñoz, Mario
author_role author
dc.contributor.none.fl_str_mv Diban Gómez, Nazely
Weidenkaff, Anke
Universidad de Cantabria
description Growing energy demand and the need to reduce CO₂ emissions have driven research into solar energy conversion technologies, such as water splitting by photoelectrochemical processes (PEC). In this context, niobium pentoxide (Nb₂O₅) is a promising material due to its stability and semiconducting properties, although its wide bandgap limits its absorption in the visible spectrum. To improve its performance, ammonolysis has been explored as a method to modify its electronic structure and enhance its photoelectrochemical response. Nb₂O₅ thin films were synthesized by dip-coating on silicon and quartz glass substrates, followed by heat treatment and ammonolysis at temperatures of 750 and 800 °C in an ammonia atmosphere. Structural characterization confirmed the formation of Nb₂O₅ with a pseudohexagonal structure, while X-ray photoelectron spectroscopy (XPS) analysis demonstrated the incorporation of nitrogen in the ammonia-treated samples. The performance of the photoelectrodes was evaluated through PEC tests under UV (500 W/m²) and visible (1000 W/m²) light illumination. On silicon substrates, films ammonolyzed at 800 °C showed a significant increase in photogenerated current under UV irradiation (~1 mA), indicating an improvement in charge separation efficiency. However, the response in the visible spectrum remained low (~100 μA), suggesting that although ammonolysis slightly reduces the bandgap, absorption is still insufficient for efficient visible light conversion. In contrast, films on quartz glass exhibited negligible photoelectrochemical activity, indicating that this substrate does not favor charge transport under the evaluated conditions. Post-PEC XPS analysis revealed that the ammonolyzed samples suffered from charging effects, indicating a loss of conductivity. The survey spectrum showed an increase in oxygen and carbon content, likely due to contamination from the electrolyte or reaction intermediates. Additionally, the emergence of more pronounced silicon peaks suggests degradation or partial detachment of the thin film during electrochemical testing. The chemical stability evaluation was hindered by these charging effects, preventing a conclusive assessment of post-PEC oxidation states and composition. In conclusion, ammonolysis at 800 °C enhances the PEC activity of Nb₂O₅ in the UV range but does not significantly improve its efficiency in the visible spectrum. Furthermore, the post-PEC analysis indicates that the thin films may degrade or detach over time under electrochemical conditions. These findings highlight the need for additional strategies, such as doping, heterostructure formation, or improved stabilization techniques, to optimize the material for long-term PEC applications.
publishDate 2025
dc.date.none.fl_str_mv 2025
2025-04-30
dc.type.none.fl_str_mv master thesis
http://purl.org/coar/resource_type/c_bdcc
NA
http://purl.org/coar/version/c_be7fb7dd8ff6fe43
dc.type.openaire.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
dc.identifier.none.fl_str_mv https://hdl.handle.net/10902/36325
url https://hdl.handle.net/10902/36325
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivatives 4.0 International
http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivatives 4.0 International
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eu_rights_str_mv openAccess
dc.source.none.fl_str_mv reponame:UCrea Repositorio Abierto de la Universidad de Cantabria
instname:Universidad de Cantabria (UC)
instname_str Universidad de Cantabria (UC)
reponame_str UCrea Repositorio Abierto de la Universidad de Cantabria
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