Porous single crystal combines the advantages of long-range ordering lattice structure and disorderly connected porous structure. With clear lattice structure, precise chemical composition, determinate termination surface, and the active surface with high distortion and continuousity, porous single crytal is of great significance to the study of the table interface structure and catalytic mechanism in various practical catalytic reactions.  

In a study published in Angew. Chem. Int. Ed., a research group led by Prof. XIE Kui from Fujian Institute of Research on the Structure of Matter (FJIRSM) of the Chinese Academy of Sciences has grown the porous single crystal Ta₃N₅ at two centimeter scale and controlled the orientations of multiple crystal planes precisely.

The researchers found that the crystal plane of the porous single crystal can be controlled through a lattice reconstruction strategy in relation to lattice match and lattice channel. The porous Ta₃N₅ single crystals with planes of (002), (023), and (041) at two centimeter scale were grown, respectively. For the large porous single crystal Ta₃N₅, the three dimensional connected porous structure not only reduces photon scattering effectively, but also provides active surfaces sufficiently. 

The single crystal skeleton enhances the efficiency of carrier separation significantly. The porous single crystal photoanode shows enhanced photoeletrochemical performance 20 times than traditional polycrystalline materials, and excellent conversion rate as well as selectivity of the photochemical oxidizing alcohol to aldehyde/ketone.  

Besides, the researchers proposed facet engineering to improve light absorption, exciton lifetime and transmission performance. Porous Ta₃N₅ single crystals enhanced the photoelectrochemical oxidation of alcohol. Particularly, the product selectivity is affected by the Ta-N coordination structures of different crystal planes. The (002) facet showed the highest performance of alcohol conversion of >99% and aldehyde / ketone selectivity of >99%.  

This study provides a new pathway to develop efficient photoelectrodes and to enhance material functionalities.