Ba₂AsGaSe₅: A New Quaternary Selenide with the Novel [AsGaSe₅]^4– Cluster and Interesting Photocatalytic Properties

Abstract

The new zero-dimensional selenide Ba₂AsGaSe₅ was synthesized via a solid-state reaction at 900 °C. It belongs to the orthorhombic space group <i>Pnma</i> with <i>a</i> = 12.632(3) Å, <i>b</i> = 8.9726(18) Å, <i>c</i> = 9.2029(18) Å, and <i>Z</i> = 4. In the structure, the As atom adopts trigonal-pyramidal coordination owing to the stereochemically active 4s² lone pair electrons and the Ga atom is tetrahedrally coordinated with four Se atoms. The AsSe₃ trigonal pyramids share edges with GaSe₄ tetrahedra to form novel [AsGaSe₅]^4– clusters, which are further separated from each other by Ba²⁺ cations. The optical band gap was determined as 1.39 eV according to UV–vis–NIR diffuse reflectance spectroscopy. Interestingly, the photocatalytic behavior investigated by decomposing rhodamine B indicates that the compound displays a 6.5 times higher photocatalytic activity than does P25