Unraveling the Structure-Property Correlations in Durable Multimetal Oxyhalide Photocatalysts

Heterogeneous catalysis, such as photocatalytic water splitting using semiconductors that harvest solar energy, poses a useful solution to ever-rising energy and environmental concerns. Recently bismuth-based layered perovskite inorganic semiconductors have emerged as promising photocatalysts. The activity and durability of these materials rely on the structure-property correlations. In this work, we have studied the local structure of bismuth-, tantalum- and gadolinium-based multimetal perovskite intergrowth oxychloride photocatalyst in depth. The local crystal and electronic structures of the oxyhalide intergrowths were investigated using advanced electron microscopy and synchrotron X-ray total scattering methods. The pair distribution function analysis of the X-ray total scattering data revealed the local symmetry and tilting of TaO₆ octahedra in the intergrowth crystal structure. In order to investigate the degree of stacking disorder in the intergrowth structure, supercells were modeled and refined on the experimental X-ray diffraction patterns. The atomic displacements in the nanoscale structure of the intergrowth materials were resolved to several picometer accuracy using aberration-corrected scanning transmission electron microscopy and converged-beam electron diffraction studies. We observed greater catalytic efficiency in intergrowths with greater tilting of the Ta octahedra, thereby establishing a useful structure-property relationship. We believe our methodology shown here can be used as a framework to develop photocatalysts with tunable optoelectronic properties.