Influence of the molten SrCl2 treatment on the surface structure and photochemical reactivities of SrTiO3

Abstract

Al-doped SrTiO3 synthesized in a SrCl2 melt is among the most efficient known photocatalysts for water splitting. Although the effect of Al3+ incorporation has been widely discussed, the role of the molten SrCl2 remains unclear. Herein, we report the influence of the molten SrCl2 treatment and a comparable molten KCl treatment on the surface structure and composition of SrTiO3 using AFM and XPS. The hydrogen evolution rates of particulate Al-doped SrTiO3 photocatalysts were measured with a parallelized and automated photochemical reactor. In SrCl2, it is found that 3 % to 5 % of the SrTiO3 dissolves in the melt, revealing a new hydroxyl-rich surface. The melt reacts with the alumina crucible to form Sr3Al2O6, ultimately leading to the elimination of the melt. In addition, the surface potential difference between (100) and (110) surfaces increases from 0.07 V to 0.21 V after the treatment, allowing for enhanced separation of photogenerated charge carriers and leading to improved photocatalytic reactivity. When heated in KCl, the SrTiO3 surfaces reconstruct and this changes the spatial distribution of photocathodic and photoanodic reaction sites.