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Hydrothermal synthesis of iridium-substituted NaTaO3 perovskites

DOI: 10.3390/nano11061537 DOI Help

Authors: David L. Burnett (University of Warwick) , Christopher D. Vincent (University of Warwick) , Jasmine A. Clayton (University of Warwick) , Reza J. Kashtiban (University of Warwick) , Richard I. Walton (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nanomaterials , VOL 11

State: Published (Approved)
Published: June 2021
Diamond Proposal Number(s): 8708

Open Access Open Access

Abstract: Iridium-containing NaTaO3 is produced using a one-step hydrothermal crystallisation from Ta2O5 and IrCl3 in an aqueous solution of 10 M NaOH in 40 vol% H2O2 heated at 240 °C. Although a nominal replacement of 50% of Ta by Ir was attempted, the amount of Ir included in the perovskite oxide was only up to 15 mol%. The materials are formed as crystalline powders comprising cube-shaped crystallites around 100 nm in edge length, as seen by scanning transmission electron microscopy. Energy dispersive X-ray mapping shows an even dispersion of Ir through the crystallites. Profile fitting of powder X-ray diffraction (XRD) shows expanded unit cell volumes (orthorhombic space group Pbnm) compared to the parent NaTaO3, while XANES spectroscopy at the Ir LIII-edge reveals that the highest Ir-content materials contain Ir4+. The inclusion of Ir4+ into the perovskite by replacement of Ta5+ implies the presence of charge-balancing defects and upon heat treatment the iridium is extruded from the perovskite at around 600 °C in air, with the presence of metallic iridium seen by in situ powder XRD. The highest Ir-content material was loaded with Pt and examined for photocatalytic evolution of H2 from aqueous methanol. Compared to the parent NaTaO3, the Ir-substituted material shows a more than ten-fold enhancement of hydrogen yield with a significant proportion ascribed to visible light absorption.

Journal Keywords: perovskite; tantalate; crystallisation; nanocrystals; photocatalysis; water splitting

Diamond Keywords: Photocatalysis

Subject Areas: Materials, Chemistry

Instruments: B18-Core EXAFS

Discipline Tags:

Chemistry Inorganic Chemistry Material Sciences Metallurgy Perovskites

Technical Tags:

Spectroscopy X-ray Absorption Near Edge Structure (XANES) X-ray Absorption Spectroscopy (XAS)