The design and synthesis of semi-conduct photo-catalytic materials and study on their facet control have become hot topics in field of photo-catalysis. However, currently reported heterogeneous materials have certain shortcomings resulting from their morphological and structural defects, including low photo-induced charge separation efficiency and low catalytic activity under visible light. Thus, the design and preparation of photocatalytic nanomaterials with highly efficient electron-hole separation structure, and controlled synthesis of facets with high activity have been problems to be urgently solved.

The energy and nano catalytic materials for environment research group at the Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS), have been long engaged in the study on Ag₃PO₄ structures and their photo-catalytic performance. They have developed several facile methods for the fabrication of Ag₃PO₄ structures with excellent photo-catalytic performance.

Firstly, the group has demonstrated selective growth of Ag₃PO₄ submicro-cubes on Ag nanowires to construct necklace-like hetero-photocatalysts. This novel hetero-structure exhibits much higher activity than both pure Ag₃PO₄ cubes and Ag nanowires for degradation of organic contaminants under visible light irradiation, which may be primarily ascribed to highly efficient charge separation at the contact interfaces as well as rapid electron export through Ag nanowires. The work has been published inJ. Mater. Chem.(J. Mater. Chem.2012, 22, 14847). Then they have demonstrated that metallic Ag nanocrystals can be selectively formed on the entire surface, edges and partial {100} facets, or only edges of single-crystalline Ag₃PO₄ submicro-cubes by simply adjusting the concentrations of ammonia. The work has been published in Chem. Eur. J.(Chem. Eur. J.2012, 18, 14272).

After they have prepared Ag3PO4 sub-microcubes with exposed {100} facets, they have further deepened the study. They have fabricated tetrahedral Ag₃PO₄ submicro-crystals in high yield by directly reacting commercial Ag foils with H₂O₂ and NaH₂PO₄ in aqueous solution at room temperature. These tetrahedral Ag₃PO₄ exhibited much higher photocatalytic activities than the irregular and cubic Ag₃PO₄ nanocrystals and commercial N-doped TiO2 under visible-light irradiation. The work has been published in J. Mater. Chem. A (J. Mater. Chem. A2013,1, 2387) and Phys. Chem. Chem. Phys.(Phys. Chem. Chem. Phys.2012,14,14486).

Recently, they have demonstrated for the first time the fabrication of concave trisoctahedral Ag₃PO₄ microcrystals enclosed by {221} and {332} facets based on the heteroepitaxial growth procedure, which exhibit much higher photocatalytic activities than cubic Ag₃PO₄ and commercial N-doped TiO₂. With density functional theory (DFT) calculations, researchers have found that Ag₃PO₄ {221} 

SEM image, UV-vis diffusive reflectance spectra and photocatalytic activities of trisoctahedral Ag3PO4microcrystals. (Imagy by BI Yingpu et al.)

and {332} facets possess higher surface energy, which should be a significant contribution to the enhanced photocatalytic activity. Moreover, the Au@Ag nanorods embedded inside TOH Ag₃PO₄ can result in the fast separation of photoexcited electron–hole pairs from their hetero-interface and thus improve the photocatalytic efficiency. This fundamental study shows a novel morphological control strategy, which may be adapted for the preparation of other semiconductor materials for photocatalytic and photoelectric applications. The work has been published in Chem. Commun.(Chem. Commun.2013, 49, 636).

 

The work has received support from the National Natural Science Foundation of China.