In situ epitaxial growth of Ag3PO4 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: London Royal Society of Chemistry 01.10.2019
• Subjects: Anions; Aqueous solutions; Catalytic activity; Crystal defects; Current carriers; Decoloring; Electric bridges; Electric fields; Epitaxial growth; Hematite; Inorganic chemistry; Ions; Liquid phases; Nanostructure; Nanotubes; Nucleation; Organic chemistry; Oxidation; Phosphates; Photocatalysis; Pollutants; Quantum dots; Reaction kinetics; Rhodamine; Silver compounds; Strategy; X ray photoelectron spectroscopy
• ISSN: 2052-1545; 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 Ag3PO4 quantum dots (QDs) on the external surface of hematite (Fe2O3) nanotubes (NTs) (Ag3PO4/Fe2O3 NT-HNSs), by intentionally employing chemically adsorbed phosphate anions on the surface of Fe2O3 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 Fe2O3 NTs play the dual functions of heterogeneous nucleation and in situ epitaxial growth of Ag3PO4 QDs along the direction of (311) on the (113) crystal plane of Fe2O3 NTs. That is, they precipitate Ag+ ions via gradual dissociation of free phosphate anions and so generate Ag3PO4 QDs, and they serve as a bridge and bond for in situ epitaxial growth of Ag3PO4 QDs on Fe2O3NTs. Due to the unique coupling of the hetero-interfaces and internal electric field, the as-obtained Ag3PO4/Fe2O3 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 Fe2O3 NTs (9.1 × 10−4 min−1), single Ag3PO4 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.