Sol-Gel Auto-Combustion Synthesis of Ca2Fe2O5 Brownmillerite Nanopowders and Thin Films for Advanced Oxidation Photoelectrochemical Water Treatment in Visible Light
Journal of Environmental Chemical Engineering 2019
Mārtiņš Vanags, Arnita Spule, Kamila Gruškeviča, Svetlana Vihodceva, Aile Tamm, Sergei Vlassov, Andris Šutka

This study describes a straightforward Ca2Fe2O5 brownmillerite nanopowder and thin film synthesis by the water-based sol-gel auto-combustion method. The material characterization results confirmed the phase pure narrow bandgap Ca2Fe2O5 nanoparticle formation. The surface area of synthesized nanopowder was 13.55 m2/g. Powders at loading 1 g/l exhibit high visible light photocatalytic activity by degrading 10 mg/l methylene blue in water in 120 min confirmed by total organic carbon studies. The high visible light photocatalytic activity is related to Ca2Fe2O5 narrow band gap and high reduction potential of its conduction band which triggers the formation of superoxide radical . The limited chemical stability for Ca2Fe2O5 nanopowders was observed due to self-reduction under photocatalytic conditions. The degradation rate constant decreased almost five times already in the second photocatalysis cycle. Further, we are demonstrating the application of Ca2Fe2O5 films in the photoelectrochemical water treatment (PECWT) process. We show that brownmillerite films are becoming stable against photo-corrosion under positive bias in PECWT and could be suitable for dye degradation in water. In the PECWT process, the Ca2Fe2O5 is protected from self-reduction since the photoinduced electron under positive bias is moved away to the Pt electrode. Under short circuit or biased (0.5 V) conditions the rate constant for MB degradation is decreased only for approximately 15% in 6 cycles.


Keywords
Iron oxide, Photocatalysis, Dye degradation, Photo-Corrosion, Stability
DOI
10.1016/j.jece.2019.103224
Hyperlink
https://www.sciencedirect.com/science/article/pii/S2213343719303471

Vanags, M., Spule, A., Gruškeviča, K., Vihodceva, S., Tamm, A., Vlassov, S., Šutka, A. Sol-Gel Auto-Combustion Synthesis of Ca2Fe2O5 Brownmillerite Nanopowders and Thin Films for Advanced Oxidation Photoelectrochemical Water Treatment in Visible Light. Journal of Environmental Chemical Engineering, 2019, Vol. 7, No. 4, pp.103224-103224. ISSN 2213-3437. Available from: doi:10.1016/j.jece.2019.103224

Publication language
English (en)
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