SYNTHESIS OF HIGHLY POROUS PHOTOACTIVE WO3 FOR GENERATION OF ClO-

Synthesis of Highly porous photoactive WO₃ for generation of ClO^-

M. Parvin, M. Petrulevičienė, I. Savickaja, V. Pakštas, A. Naujokaitis, R. Ramanauskas, J. Juodkazytė

Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius 10257, Lithuania

maliha.parvin@ftmc.lt

Photoelectrochemical (PEC) generation of reactive chlorine species has attracted considerable attention because synthesis of H₂ on cathode can be coupled with production of high added-value chemicals such as HClO, H₂O₂, etc. on suitable photoanode [1]. Chloride anion oxidation (or hypochlorite production) is an attractive alternative to the oxygen evolution reaction due to a large amount of seawater as natural electrolyte on Earth and the massive application of hypochlorites in industrial water disinfection and sanitization [2-3]. In this study, porous WO₃ films were formed on fluorine-doped tin oxide (FTO) substrates by low temperature chemical bath deposition (CBD) and tested for PEC chloride oxidation.

To prepare WO₃ photoanode, Na₂WO₄.2H₂O was dissolved in deionized water under constant stirring, which was followed by the addition of citric acid and 3M HCl consecutively.  Cleaned FTO substrates were immersed in the above solution and the deposition was allowed to proceed for two hours. The films were annealed at 400^oC in air. The same procedure was repeated four times to obtain layers with increasing thickness. After first coating procedure comparably “thin” WO₃ nanostructured films with a layer thickness of several hundred nanometers and nanosheet morphology are typically obtained. After four chemical bath deposition cycles, several micrometers thick porous WO₃ layers were formed.

Cyclic voltammograms (CV) of one-layer WO₃ photoanode were measured in 0.5 M NaCl under dark and light to evaluate the PEC performance of the film. The photocurrents of CBD-deposited WO₃ films were found to be increasing with the layer thickness. Faradaic efficiency of PEC formation of ClO^- was evaluated.

Acknowledgement:

Acknowledgment: This research was funded by the M-ERA.NET project “Multiscale computer modelling, synthesis and rational design of photo(electro)catalysts for efficient visible-light-driven seawater splitting” (CatWatSplit), Ref. Number: project8168, under a grant agreement Nr. S-M-ERA.NET-21-3 with the Research Council of Lithuania (LMTLT).

References

1. X. Li et al. Appl. Catal. B Environ. 296 (2021) 120387.

2. A. Breuhaus-Alvarez, et al. J. Phys. Chem. C. 125 (2021) 8543.

3. S. Iguchi, et. al. Sustain. Energy Fuels. 2 (2018) 155.