Synergistic dye/photocatalyst interconnections for activating efficient light-induced degradation pathways

Abstract

The development of high performance photocatalysts (PCs) can be considered an efficient strategy to alleviate the growing global concern over environmental water pollution. In particular, metal halide perovskites (MHPs) have been proposed as suitable materials for removing various contaminants. However, there is still a lack of criteria regarding the type of dyes that can be efficiently degraded by MHPs and their degradation pathways. In this study, we applied a reprecipitation approach for obtaining CsPbBr3 materials using three different polar solvents for crystallization: ethyl acetate (EA), iso-propanol (IPA), and acetone (ACE). A comprehensive morphological, structural, and optical characterization of the three resulting CsPbBr3 samples, namely, EA-CsPbBr3, IPA-CsPbBr3, and ACE-CsPbBr3, was performed. In the prototypical methylene blue photodegradation under visible-light irradiation (λ > 420 nm), EA-CsPbBr3 demonstrates the best performance among the three PCs, primarily due to the largest surface area and smallest particle size. This highlights the role of the crystallization solvent in the morphological control of the corresponding PCs. The EA-CsPbBr3 material was systematically employed in the photodegradation of different xanthene-based dyes, resulting in extremely efficient decomposition of environmentally persistent halogen-containing dyes (eosin B, erythrosin B, and rose Bengal). In these cases, the pseudo-first order reaction rate constants (k = 0.33094–0.62243 min−1) are one order of magnitude higher than those recorded for the degradation of halogen-free rhodamine B (k = 0.05230 min−1) and methylene blue (k = 0.02098 min−1). The investigations on the photo-degradation mechanism of eosin B demonstrate the key role of photo-injected electrons into the dye, activating the C–X bonds and the consequent radical decomposition pathways. Furthermore, we observe that the degradation kinetics remain unaltered at least five times using the recovered PC of each cycle. Therefore, this study not only consolidates the potential of CsPbBr3 materials in the dye removal but also provides new insights into the impact of synthetic methods on their photocatalytic activity and degradation pathways.