A.Šutka, M.Vanags, U.Joost, K.Šmits, J.Ruža, J.Ločs, J.Kleperis, T.Juhna

Solid-state narrow band gap semiconductor heterostructures with a Z-scheme charge-transfer mechanism are the most promising photocatalytic systems for water splitting and environmental remediation under visible light. Herein, we construct all-solid Z-scheme photocatalytic systems from earth abundant elements (Ca and Fe) using an aqueous synthesis procedure. A novel Z-scheme two-component Fe₂O₃/Ca₂Fe₂O₅ heterostructure is obtained in a straightforward manner by soaking various iron-containing nanoparticles (amorphous and crystalline) with Ca(NO₃)₂ and performing short (20 min) thermal treatments at 820 °C. The obtained powder materials show high photocatalytic performances for methylene blue dye degradation under visible light (45 mW/cm²), exhibiting a rate constant up to 0.015 min⁻¹. The heterostructure exhibits a five-fold higher activity compared to that of pristine hematite. The experiments show that amorphous iron-containing substrate nanoparticles trigger the Fe₂O₃/Ca₂Fe₂O₅ heterostructure formation. We extended our study to produce Fe₂O₃/Ca₂Fe₂O₅nanoheterostructure photoanodes via the electrochemical deposition of amorphous iron-containing sediment were used. The visible-light (15 mW/cm²) photocurrent increases from 183 μA/cm²to 306 μA/cm² after coupling hematite and Ca₂Fe₂O₅. Notably, the powders and photoanodes exhibit distinct charge-transfer mechanisms evidenced by the different stabilities of the heterostructures under different working conditions.

Published in Journal of Environmental Chemical Engineering

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