In-situ Epitaxial Growth of Ag3PO4 Quantum Dots on Hematite Nanotubes for High Photocatalytic Activities
It is of great importance for the effective construction of semiconductor hetero-nanostructures (HNSs) with a well-defined hetero-interface. As so far the highly developed liquid-phase chemical routes are often restricted from the heavy using of surfactants or/and organic solvents, inevitably introducing passivated surface and interfacial defects in the resultant HNSs. Here we have develop a novel and efficient in-situ epitaxial growth strategy to fabricate the HNSs of Ag3PO4 quantum dots (QDs) on the external surface of hematite (Fe2O3) nanotubes (NTs) (Ag3PO4/Fe2O3), by intentionally employing the chemically adsorbed phosphate anions on the surface of Fe2O3 NTs to control the reaction kinetics of phosphate anions and Ag+ ions in an aqueous solution. Of this synthetic strategy, the chemically adsorbed phosphate anions on the surface of Fe2O3 NTs play dual functions for the heterogeneous nucleation and in-situ epitaxial growth of Ag3PO4 quantum dots (QDs) along the direction of (311) on the (113) crystal plane of Fe2O3 NTs, i.e., they precipitate Ag+ ions via gradual dissociation of free phosphate anions and generate Ag3PO4 QDs, and serve as a bridge and bond for in-situ epitaxial growth of Ag3PO4 QDs on Fe2O3 NTs. Due to the unique coupling hetero-interfaces and internal electric field, the as-obtained Ag3PO4/Fe2O3 HNSs show efficient separation of photogenerated charge carriers and remarkable enhancement of their reduction and oxidation abilities by a Z-scheme photocatalytic forms, significantly improved visible light photocatalytic activity for organic pollutant RhB decolorization. They exhibit a photocatalytic rate constant as large as 3.6×10-2 min-1, two orders of magnitude 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 them (7.1×10-4 min-1), suggesting a highly efficient photocatalyst. The in-situ epitaxial growth strategy proposed here constitutes a novel example for the fine construction of hetero-nanostructures in the solar utilization.