Suppressed Charge Recombination in Hematite Photoanode via Protonation and Annealing

  • Wenping Si*
    Wenping Si
    Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
    Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
    *(W.S.) E-mail: [email protected]
    More by Wenping Si
  • Fatima Haydous
    Fatima Haydous
    Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
  • Ugljesa Babic
    Ugljesa Babic
    Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
  • Daniele Pergolesi
    Daniele Pergolesi
    Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
    Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
  • , and 
  • Thomas Lippert
    Thomas Lippert
    Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
    Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
Cite this: ACS Appl. Energy Mater. 2019, 2, 8, 5438–5445
Publication Date (Web):June 13, 2019
Copyright © 2019 American Chemical Society
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Hematite as promising photoanode for solar water splitting suffers from severe bulk and surface charge recombination. This work describes that a protonation–annealing treatment can effectively suppress both bulk and surface charge recombination in hematite. Protons/electrons are electrochemically incorporated into hematite under 0.2 VRHE followed by annealing at 120 °C. The photocurrent density increases from ∼0.9 to 1.8 mA cm–2 at 1.23 VRHE under 1 sun, and further to 2.7 mA cm–2 after loading cobalt phosphate, stabilizing at round 2.4 mA cm–2. A cathodic shift of the onset potential of photocurrent is also observed. H2O2 oxidation, impedance spectroscopy, and Mott–Schottky measurements show that the protonation suppresses bulk recombination and enhances donor density, but introducing more surface recombination. The annealing reduces surface recombination, while preserving relatively high bulk charge separation efficiency. Different from previous reports on the electrochemically reduced hematite, this work demonstrates that the performance improvement should be ascribed to the proton incorporation instead of the formation of Fe3O4 or metal Fe. This facile treatment by protonation and annealing could be applied in other semiconductors to promote the development of high performing photoelectrodes.

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.9b00420.

  • Additional experimental details including optimization of annealing parameters, photograph of hematite, photocurrents for anneal-only hematite, Nyquist plot under light at 0.98 VRHE, open-circuit potentials, electrochemical surface area, photovoltage calculations, AFM images, and XRD patterns (PDF)

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Cited By

This article is cited by 9 publications.

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  2. Paula Quitério, Arlete Apolinário, David Navas, Sérgio Magalhães, Eduardo Alves, Adélio Mendes, Célia Tavares Sousa, João Pedro Araújo. Photoelectrochemical Water Splitting: Thermal Annealing Challenges on Hematite Nanowires. The Journal of Physical Chemistry C 2020, 124 (24) , 12897-12911.
  3. Ka-Te Chen, Chia-Hsun Hsu, Fang-Bin Ren, Can Wang, Peng Gao, Wan-Yu Wu, Shui-Yang Lien, Wen-Zhang Zhu. Influence of annealing temperature of nickel oxide as hole transport layer applied for inverted perovskite solar cells. Journal of Vacuum Science & Technology A 2021, 39 (6) , 062401.
  4. Satirtha K Sarma, Ratan Mohan, Anupam Shukla. Fabrication of tin‐doped hematite modified with NiFe‐LDH nanoflakes for highly efficient solar water splitting. International Journal of Energy Research 2021, 45 (14) , 19869-19882.
  5. M. Geerthana, K. Ramachandran, P. Maadeswaran, M. Navaneethan, S. Harish, R. Ramesh. Activation of α-Fe 2 O 3 Photoanode by Rapid Annealing Process for Photoelectrochemical Water Splitting. ECS Journal of Solid State Science and Technology 2021, 10 (6) , 061007.
  6. Dan Wang, Shuang Gao, Chuang Li, Yinglin Wang, Hancheng Zhu, Yichun Liu, Xintong Zhang. Pulse laser annealing activates titanium-doped hematite photoanodes for photoelectrochemical water oxidation. Applied Surface Science 2020, 528 , 147062.
  7. Liqun Wang, Wenping Si, Yueyu Tong, Feng Hou, Daniele Pergolesi, Jungang Hou, Thomas Lippert, Shi Xue Dou, Ji Liang. Graphitic carbon nitride (g‐C 3 N 4 )‐based nanosized heteroarrays: Promising materials for photoelectrochemical water splitting. Carbon Energy 2020, 2 (2) , 223-250.
  8. Aryane Tofanello, Shaohua Shen, Flavio Leandro de Souza, Lionel Vayssieres. Strategies to improve the photoelectrochemical performance of hematite nanorod-based photoanodes. APL Materials 2020, 8 (4) , 040905.
  9. Huanhuan Cao, Wenping Si, Wenlei Guo, Tao Zhang, Yonghuan Han, Feng Hou, Ji Liang. KCl flux suppresses surface recombinations of hematite photoanode for water oxidation. Surface Innovations 2020, 8 (3) , 130-137.