Highly active Ta₂O₅ microcubic single crystals: facet energy calculation, facile fabrication and enhanced photocatalytic activity of hydrogen production

This work has identified Ta₂O₅ {001} facets as the high-energy facet by first-principles theory, and demonstrated the first example of tantalum oxide facet engineering. Ta₂O₅ microcubic single crystals (MCSCs) with a large percentage exposure of highly active facets take advantage of the unique crystal structure and cubic morphology of the precursor tantalum oxychlorides, as well as the characteristics of a topological transformation synthesis. In our protocol, the heat treatment of the TaO_2.18Cl_0.64 microcube precursor only enables an intra-layer transition but preserves the {001} facets due to the strong 180° Ta–O–Ta structure between layers. Consequently, mesoporous Ta₂O₅ MCSCs with high-energy facet exposure are produced. The as-obtained Ta₂O₅ MCSCs exhibit a remarkably enhanced photocatalytic hydrogen production activity for their specific surface area due to the enlarged percentage of exposed {001} facets, which possess the largest density and highest quality of hyperactive sites for the photocatalytic reaction. The results here may provide a plausible approach for both the facet engineering of metal oxides with similar layer structures and the enhancement of Ta₂O₅ chemical activities.