The contrasting effect of the Ta/Nb ratio in (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-: XTaxO15 crystals on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives

Mirabbos Hojamberdiev, Maged F. Bekheet, Ehsan Zahedi, Hajime Wagata, Junie Jhon M. Vequizo, Akira Yamakata, Kunio Yubuta, Aleksander Gurlo, Kazunari Domen, Katsuya Teshima

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Abstract

The effect of the Ta/Nb ratio in the (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-xTaxO15 (0 ≤ x ≤ 4) crystals grown by a KCl flux method on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives BaNb1-xTaxO2N (0 ≤ x ≤ 1) was investigated. The Rietveld refinement of X-ray data revealed that all Ba5Nb4-xTaxO15 samples were well crystallized in the space group P3m1 (no. 164). Phase-pure BaNb1-xTaxO2N (0 ≤ x ≤ 1) porous structures were obtained by nitridation of the flux-grown oxide crystals at 950 °C for 20, 25, 30, 35, and 40 h, respectively. The absorption edge of BaNb1-xTaxO2N (0 ≤ x ≤ 1) was slightly shifted from 720 to 690 nm with the increasing Ta/Nb ratio. The O2 evolution rate gradually progressed and reached the highest value (127.24 μmol in the first 2 h) with the Ta content up to 50 mol% but decreased at 75 and 100 mol% presumably due to the reduced specific surface area and high density of structural defects, such as grain boundaries acting as recombination centers, originated from high-temperature nitridation for prolonged periods. Transient absorption spectroscopy provided evidence for the effect of the Ta/Nb ratio on the behavior and energy states of photogenerated charge carriers, indicating a direct correlation with photocatalytic water oxidation activity of BaNb1-xTaxO2N.

Original languageEnglish
Pages (from-to)12559-12568
Number of pages10
JournalDalton Transactions
Volume45
Issue number31
DOIs
Publication statusPublished - 2016 Jan 1

ASJC Scopus subject areas

  • Inorganic Chemistry

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