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Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting

Hermans, Yannick ; Klein, Andreas ; Sarker, Hori Pada ; Huda, Mohammad N. ; Junge, Henrik ; Toupance, Thierry ; Jaegermann, Wolfram (2021):
Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting. (Publisher's Version)
In: Advanced Functional Materials, 30 (10), Wiley, ISSN 1616-301X, e-ISSN 1616-3028,
DOI: 10.26083/tuprints-00019358,
[Article]

Abstract

CuFeO₂ is recognized as a potential photocathode for photo(electro)chemical water splitting. However, photocurrents with CuFeO₂-based systems are rather low so far. In order to optimize charge carrier separation and water reduction kinetics, defined CuFeO₂/Pt, CuFeO₂/Ag, and CuFeO₂/NiOx(OH)y heterostructures are made in this work through a photodeposition procedure based on a 2H CuFeO₂ hexagonal nanoplatelet shaped powder. However, water splitting performance tests in a closed batch photoreactor show that these heterostructured powders exhibit limited water reduction efficiencies. To test whether Fermi level pinning intrinsically limits the water reduction capacity of CuFeO₂, the Fermi level tunability in CuFeO₂ is evaluated by creating CuFeO₂/ITO and CuFeO₂/H₂O interfaces and analyzing the electronic and chemical properties of the interfaces through photoelectron spectroscopy. The results indicate that Fermi level pinning at the Fe³⁺/Fe²⁺ electron polaron formation level may intrinsically prohibit CuFeO₂ from acquiring enough photovoltage to reach the water reduction potential. This result is complemented with density functional theory calculations as well.

Item Type: Article
Erschienen: 2021
Creators: Hermans, Yannick ; Klein, Andreas ; Sarker, Hori Pada ; Huda, Mohammad N. ; Junge, Henrik ; Toupance, Thierry ; Jaegermann, Wolfram
Origin: Secondary publication service
Status: Publisher's Version
Title: Pinning of the Fermi Level in CuFeO₂ by Polaron Formation Limiting the Photovoltage for Photochemical Water Splitting
Language: English
Abstract:

CuFeO₂ is recognized as a potential photocathode for photo(electro)chemical water splitting. However, photocurrents with CuFeO₂-based systems are rather low so far. In order to optimize charge carrier separation and water reduction kinetics, defined CuFeO₂/Pt, CuFeO₂/Ag, and CuFeO₂/NiOx(OH)y heterostructures are made in this work through a photodeposition procedure based on a 2H CuFeO₂ hexagonal nanoplatelet shaped powder. However, water splitting performance tests in a closed batch photoreactor show that these heterostructured powders exhibit limited water reduction efficiencies. To test whether Fermi level pinning intrinsically limits the water reduction capacity of CuFeO₂, the Fermi level tunability in CuFeO₂ is evaluated by creating CuFeO₂/ITO and CuFeO₂/H₂O interfaces and analyzing the electronic and chemical properties of the interfaces through photoelectron spectroscopy. The results indicate that Fermi level pinning at the Fe³⁺/Fe²⁺ electron polaron formation level may intrinsically prohibit CuFeO₂ from acquiring enough photovoltage to reach the water reduction potential. This result is complemented with density functional theory calculations as well.

Journal or Publication Title: Advanced Functional Materials
Journal volume: 30
Number: 10
Publisher: Wiley
Collation: 10 Seiten
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Electronic Structure of Materials (ESM)
11 Department of Materials and Earth Sciences > Material Science > Surface Science
Date Deposited: 26 Aug 2021 12:27
DOI: 10.26083/tuprints-00019358
Official URL: https://tuprints.ulb.tu-darmstadt.de/19358
URN: urn:nbn:de:tuda-tuprints-193588
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