WO₃ Photoanodes for Photoelectrochemical Applications

Abstract

WO₃ layers were prepared by spray pyrolysis of a peroxotungstic acid solution on FTO/glass substrates. Investigated parameters were layer thickness and influence of post-annealing in air. Films deposited at 250 °C were amorphous. Post-annealing at 550 °C for 2 h resulted in the formation of monoclinic crystalline structure. A comprehensive account of electrochemical efficiency in terms of IPCE for WO₃ films as a function of the three parameters (wavelength, thickness and direction of light incidence) fully characterizing the photoelectrodes is presented here for the first time. The highest improvement in crystallinity and also the highest photocurrent response was found for WO₃ layers deposited at 250 °C and post-annealed at 550 °C, namely 1.9 mA/cm² (in 0.1 M HClO₄ at 1.6 V vs. Ag/AgCl) under irradiation with a solar simulator (AM 1.5, 100 mW/cm²) and IPCE = 0.5 at 369 nm (front side irradiation), which is comparable with values obtained by other deposition techniques (e.g., hydrothermal or sol gel). Spray pyrolysis as a method of fabricating WO₃ electrodes has the advantage of being able to produce large electrodes for use in practical applications.

Keywords

WO₃ / Spray pyrolysis / Crystallinity / Photocurrent / IPCE

Supplementary Materials

The following supporting information can be found at: https://www.sciepublish.com/article/pii/445, Figure S1: AFM phase images (left) and 3D height AFM images (right) of (a) FTO/glass substrate, (b) 4.2 µm thick WO₃ layer deposited at 250 °C on FTO/glass substrate and post-annealed at 550 °C for 2 h. The black bar in AFM phase images represents 500 nm; Figure S2: Tauc plot for WO₃ films deposited at 250 °C and post-annealed in air (550 °C, 2 h), layer thickness 4.2 µm.

Acknowledgements

Jiří Olejníček is acknowledged for Raman spectroscopy and Hana Tarábková for AFM analysis.

Author Contributions

B.R.: Investigation, Data curation, T.I.: Investigation, Data curation, Original draft, Writing—review & editing, H.K.: Investigation, M.N.-S.: Conceptualization, Original draft, Writing—review & editing, J.K.: Funding acquisition, Conceptualization, Writing—review & editing.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available at https://doi.org/10.5281/zenodo.14605450. Data set for “WO₃ photoanodes for photoelectrochemical applications” (Original data) (Zenodo).

Funding

This work was supported by the project “Sensors and Detectors for Future Information Society-SENDISO reg. n. CZ.02.01.01/00/22_008/0004596” by the Programme Johannes Amos Comenius, call “Excellent Research”. This work was also supported by the Czech Science Foundation (project number 23-05266S) and by the grant of Specific University Research (UCT Prague)-Grant A2_FCHT_2024_002.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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