Tuning activities of K_1.9Na_0.1Ta₂O ₆·2H₂O nanocrystals in photocatalysis by controlling exposed facets

Morphology-controlled synthesis of tantalates is a major challenge in the field of material science. Herein, an innovative strategy has been developed for controllably synthesizing K_1.9Na_0.1Ta₂O ₆·2H₂O (KNTO) nanocrystals shaped as octahedra and nanosheets without using any capping agents. The obtained nanocrystals show high activity in photocatalytic H₂ evolution from CH₃OH/H ₂O solution, and their performance closely depends on the exposed facets, in which the {111}-facet-bounded nanooctahedra exhibit more than 3 times higher activity than the nanosheets dominated with {101} facets. The influence of surface atomic structure and electronic band structure on the photocatalytic properties of the KNTO nanocrystals is systematically studied. This is the first report for the facet controllable synthesis of tantalate materials with highly regular shapes. The present approach is anticipated as a general strategy for controllable synthesis of tantalate materials and also provides feasibility for rational design and activity optimization of shape-controlled photocatalysts for H₂ production.