Reduction and Diffusion of Cr-Oxide Layers into P25, BaLa4Ti4O15, and Al:SrTiO3 Particles upon High-Temperature Annealing

Abdulrahman S Alotabi; Thomas D Small; Yanting Yin; D J Osborn; Shuhei Ozaki; Yuki Kataoka; Yuichi Negishi; Kazunari Domen; Gregory F Metha; Gunther G Andersson

doi:10.1021/acsami.3c00250

Reduction and Diffusion of Cr-Oxide Layers into P25, BaLa₄Ti₄O₁₅, and Al:SrTiO₃ Particles upon High-Temperature Annealing

ACS Appl Mater Interfaces. 2023 Mar 12. doi: 10.1021/acsami.3c00250. Online ahead of print.

Authors

Abdulrahman S Alotabi^{1

2

3}, Thomas D Small⁴, Yanting Yin^{1

3}, D J Osborn⁴, Shuhei Ozaki⁵, Yuki Kataoka⁵, Yuichi Negishi⁵, Kazunari Domen^{6

7}, Gregory F Metha⁴, Gunther G Andersson^{1

3}

Affiliations

¹ Flinders Institute for Nanoscale Science and Technology, Flinders University, Adelaide, South Australia 5042, Australia.
² Department of Physics, Faculty of Science and Arts in Baljurashi, Albaha University, Baljurashi 65655, Saudi Arabia.
³ Flinders Microscopy and Microanalysis, College of Science and Engineering, Flinders University, Adelaide 5042, Australia.
⁴ Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia.
⁵ Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
⁶ Research Initiative for Supra-Materials (RISM), Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan.
⁷ Office of University Professors, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

PMID: 36906923
DOI: 10.1021/acsami.3c00250

Abstract

Chromium oxide (Cr₂O₃) is a beneficial metal oxide used to prevent the backward reaction in photocatalytic water splitting. The present work investigates the stability, oxidation state, and the bulk and surface electronic structure of Cr-oxide photodeposited onto P25, BaLa₄Ti₄O₁₅, and Al:SrTiO₃ particles as a function of the annealing process. The oxidation state of the Cr-oxide layer as deposited is found to be Cr₂O₃ on the surface of P25 and Al:SrTiO₃ particles and Cr(OH)₃ on BaLa₄Ti₄O₁₅. After annealing at 600 °C, for P25 (a mixture of rutile and anatase TiO₂), the Cr₂O₃ layer diffuses into the anatase phase but remains at the surface of the rutile phase. For BaLa₄Ti₄O₁₅, Cr(OH)₃ converts to Cr₂O₃ upon annealing and diffuses slightly into the particles. However, for Al:SrTiO₃, the Cr₂O₃ remains stable at the surface of the particles. The diffusion here is due to the strong metal-support interaction effect. In addition, some of the Cr₂O₃ on the P25, BaLa₄Ti₄O₁₅, and Al:SrTiO₃ particles is reduced to metallic Cr after annealing. The effect of Cr₂O₃ formation and diffusion into the bulk on the surface and bulk band gaps is investigated with electronic spectroscopy, electron diffraction, DRS, and high-resolution imaging. The implications of the stability and diffusion of Cr₂O₃ for photocatalytic water splitting are discussed.

Keywords: Al-doped SrTiO3; BaLa4Ti4O15; Cr2O3 layer; P25; backward reaction; photocatalytic water-splitting; photodeposition.