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Two-step synthesis of Sillén-Aurivillius type oxychlorides to enhance the photocatalytic activity for visible-light-induced water splitting

Abstract

A two-step synthesis via polymerized complex method (2PC) was developed to improve the photocatalytic activity of a Sillén-Aurivillius oxychloride Bi4TaO8Cl and related oxychlorides for O2 evolution (i.e., water oxidation) in Z-scheme water splitting under visible light. This method uses the polymerized complex reaction to prepare a precursor oxide (e.g., Bi3TaO7), which is subsequently calcined with BiOCl to yield a pure Bi4TaO8Cl phase with smaller particle sizes than those via conventional single-step solid-state reaction (1SSR). Furthermore, time-resolved microwave conductivity (TRMC) measurements revealed that a Bi4TaO8Cl sample prepared by 2PC method at 973 K (2PC_973) achieved more than five times longer-lived charge separation than that by 1SSR at 973 K (1SSR_973), which probably arises from lower numbers of charge-recombination center produced in 2PC synthesis. Thus, synthesized Bi4TaO8Cl samples exhibited higher rate of O2 evolution (e.g.., 20 μmol h−1 for 2PC_973 vs. 4 μmol h−1 for 1SSR_973). Simultaneous water splitting into stoichiometric H2 and O2 production was demonstrated by constructing Z-scheme photocatalytic system consisting of 2PC_973, Ru-modified SrTiO3:Rh, and an Fe3+/Fe2+ shuttle redox mediator, with the external quantum efficiency of 0.9% at 420 nm, much higher than that using the sample derived from the optimized 1SSR method at 1173 K (0.4%). The 2PC synthesis was successfully expanded to other Sillén-Aurivillius type oxychlorides, Bi4NbO8Cl, Bi6NbWO14Cl and Sr2Bi3Ta2O11Cl, all of which exhibited superior water splitting activity compared to those prepared through 1SSR.

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Publication details

The article was received on 11 Apr 2018, accepted on 11 May 2018 and first published on 14 May 2018


Article type: Paper
DOI: 10.1039/C8TA03321H
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    Two-step synthesis of Sillén-Aurivillius type oxychlorides to enhance the photocatalytic activity for visible-light-induced water splitting

    A. Nakada, A. Saeki, M. Higashi, H. Kageyama and R. Abe, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA03321H

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