Modulating the External Facets of Functional Nanocrystals Enabled by Two-Dimensional Oxide Crystal Templates

[Image: see text] The nature of the external crystal facets is critical to control the (photo)catalytic properties. Two-dimensional materials can expose only one type of crystal facet among zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) materials. Controllable tuning of the nature of the external crystal facets of 2D materials is highly desirable but very challenging. Here, we show that 2D particles with the desirable crystal facet for high-performance photocatalytic H(2) generation can be obtained by using 2D metal oxide materials (i.e., nanosheets of Ca(2)Nb(3)O(10) and Ti(0.87)O(2)) as templates taking consideration of the crystal configuration of 2D oxide and target compounds. We demonstrate that anatase TiO(2) crystals grown on different nanosheet templates exhibit variations in photocatalytic hydrogen production rates from aqueous phase methanol solutions (6.7%), which can be attributed to the nature of the main crystal facet exposed. In view of the large number of 2D materials that have already been synthesized, this work offers a key to design and synthesize nanoparticles with the desirable specific external crystal facet for (photo)catalysis application.