Ionic‐Liquid‐Assisted Microwave Synthesis of Solid Solutions of Sr_1−xBa_xSnO₃ Perovskite for Photocatalytic Applications

Abstract

Nanocrystalline Sr1−xBaxSnO3 (x=0, 0.2, 0.4, 0.8, 1) perovskite photocatalysts were prepared by microwave synthesis in an ionic liquid (IL) and subsequent heat‐treatment. The influence of the Sr/Ba substitution on the structure, crystallization, morphology, and photocatalytic efficiency was investigated and the samples were fully characterized. On the basis of X‐ray diffraction results, as the Ba content in the SrSnO3 lattice increases, a symmetry increase was observed from the orthorhombic perovskite structure for SrSnO3 to the cubic BaSnO3 structure. The analysis of the sample morphology by SEM reveals that the Sr1−xBaxSnO3 samples favor the formation of nanorods (500 nm–5 μm in diameter and several micrometers long). The photophysical properties were examined by UV/Vis diffuse reflectance spectroscopy. The band gap decreases from 3.85 to 3.19 eV with increasing Ba2+ content. Furthermore, the photocatalytic properties were evaluated for the hydroxylation of terephthalic acid (TA). The order of the activities for TA hydroxylation was Sr0.8Ba0.2SnO3>SrSnO3>BaSnO3>Sr0.6Ba0.4SnO3>Sr0.2Ba0.8SnO3. The highest photocatalytic activity was observed for Sr0.8Ba0.2SnO3, and this can be attributed to the synergistic impacts of the modification of the crystal structure and morphology, the relatively large surface area associated with the small crystallite size, and the suitable band gap and band‐edge position.

Synthesis and Dissolution of Metal Oxides in Ionic Liquids and Deep Eutectic Solvents

“…ILs are particularly suitable for microwave heating. Because of their large, highly polarisable cations, a very efficient absorption of microwave irradiation makes them an effective heating medium for microwave-assisted synthesis [27]. Recently, also the combination of sonochemistry and ILs has been reported [28][29][30][31].…”

“…Mudring [91]. The reaction was also successfully performed in an ionothermal synthesis (170 • C, 20 h) before calcination [27]. Despite the reaction takes place in aqueous solution, as well, the IL prevents agglomeration and different cations influence the morphology of the nano-SrSnO 3 .…”

“…The same reaction method has been applied to Sr 1-x Ba x SnO 3 (x = 0; 0.2; 0.4; 0.6; 0.8; 1) using Ba(CH 3 COO) 2 as an additional reactant in the IL [bmim][NTf 2 ]. Solid solutions of SrSnO 3 and BaSnO 3 without any detectable impurities were obtained [27].…”

Perovskite Oxide Based Electrodes for High‐Performance Photoelectrochemical Water Splitting

“…[46][47][48][49] Additionally,t he rational selection and functional doping of A-site elements in perovskite oxides can also lead to the reduction of band gaps. [50][51][52] Intriguingly,f or some perovskite-based photoelectrodes with visible light response,they can also function as promising electrocatalysts for water splitting reactions.F or instance, LaFeO 3 ,apopular photoelectrode in PEC water splitting,has been demonstrated to catalyze electrocatalytic OER, showing potential for improved electrocatalysis when A-site Ladeficiencyi sf urther introduced. [53] Another example is oxygen-deficient nanosized BaTiO 3-d (d = 0.24), which exhibits high electrocatalytic activity for OER, outperforming the OER activity of noble-metal-based IrO 2 at relatively low overpotentials.…”

Perowskitoxid‐Elektroden zur leistungsstarken photoelektrochemischen Wasserspaltung

“…B. Cl, N, S) ersetzt werden, um so die Bandlücke zu verringern und das Vermögen zur Absorption von sichtbarem Licht zu verbessern . Zudem kann eine Verkleinerung der Bandlücken in Perowskitoxiden durch rationale Auswahl und funktionelle Dotierung der A‐Elemente realisiert werden …”