In situ epitaxial growth of Ag 3 PO 4 quantum dots on hematite nanotubes for high photocatalytic activities

• Published in: Inorganic chemistry frontiers Vol. 6; no. 10; pp. 2747 - 2755
• Main Authors: Duan, Junyuan, Xu, Leilei, Liu, Youwen, Liu, Bingxin, Zhai, Tianyou, Guan, Jianguo
• Format: Journal Article
• Language: English
• Published: 08.10.2019
• ISSN: 2052-1553; 2052-1553
• DOI: 10.1039/C9QI00744J

Effective construction of semiconductor hetero-nanostructures (HNSs) with a well-defined hetero-interface is of great importance. So far, highly developed liquid-phase chemical routes are often restricted by their heavy use of surfactants and/or organic solvents, which inevitably introduce passivated surfaces and interfacial defects in the resultant HNSs. Here, we have developed a novel and efficient in situ epitaxial growth strategy to fabricate HNSs of Ag 3 PO 4 quantum dots (QDs) on the external surface of hematite (Fe 2 O 3 ) nanotubes (NTs) (Ag 3 PO 4 /Fe 2 O 3 NT-HNSs), by intentionally employing chemically adsorbed phosphate anions on the surface of Fe 2 O 3 NTs to control the reaction kinetics of phosphate anions and Ag + ions in aqueous solution. In this synthetic strategy, the chemically adsorbed phosphate anions on the surface of the Fe 2 O 3 NTs play the dual functions of heterogeneous nucleation and in situ epitaxial growth of Ag 3 PO 4 QDs along the direction of (311) on the (113) crystal plane of Fe 2 O 3 NTs. That is, they precipitate Ag + ions via gradual dissociation of free phosphate anions and so generate Ag 3 PO 4 QDs, and they serve as a bridge and bond for in situ epitaxial growth of Ag 3 PO 4 QDs on Fe 2 O 3 NTs. Due to the unique coupling of the hetero-interfaces and internal electric field, the as-obtained Ag 3 PO 4 /Fe 2 O 3 NT-HNSs show efficient separation of photogenerated charge carriers and remarkable enhancement of their reduction and oxidation abilities by a Z -scheme photocatalytic form, significantly improving visible-light photocatalytic activity for decolorization of the organic pollutant rhodamine B. They exhibit a photocatalytic rate constant as large as 3.6 × 10 −2 min −1 , which is two orders of magnitude greater than that of single Fe 2 O 3 NTs (9.1 × 10 −4 min −1 ), single Ag 3 PO 4 QDs (1.6 × 10 −4 min −1 ) as well as the mixture of the two (7.1 × 10 −4 min −1 ), suggesting a highly efficient photocatalyst. The in situ epitaxial growth strategy proposed here constitutes a novel example for fine construction of hetero-nanostructures for solar utilization.