Research PaperPolyoxometalate/TiO2/Ag composite nanofibers with enhanced photocatalytic performance under visible light

- A series of PMo12/TiO2/Ag composite nanofibers with different content of Ag have been prepared by a facile electrospinning/calcination and in situ photodeposited route, which exhibit highly efficient and durable activity for removing of methyl orange and Cr(VI) under visible-light irradiation (λ > 420 nm).
- The O2− and OH are the main active species in the degradation process of MO. And according to the results, the possible photocatalytic mechanism of such composites working has been proposed.
- In the composite, the combination of POMs and TiO2 can not only modulate the light adsorption and redox activity of the TiO2, but also ensure the photochemical stability of the plasmonic composites because of the relative narrow band gap and strong reversible redox properties of polyoxoanion [PMo12O40]3−.
- Ag nanoparticles exhibit surface plasmon resonance (SPR) absorption, it further enhances the visible-light absorption of the composite. Additionally, it also causes intense local electromagnetic fields by SPR, which accelerates the separation of photogenerated electrons and holes.

The exploration of highly efficient and stable visible-light-driven photocatalysts for the wastewater treatment has been recognized as one of the currently most challenging topics for the environment remediation. In this paper, we report a new type of polyoxometalate-TiO2 composite nanofibers loaded with Ag nanoparticles (NPs), labeled as PMo12/TiO2/Ag-X (PMo12 = [PMo12O40]3−; X represents the weight percent (%) of Ag in PMo12/TiO2/Ag samples; X = 3.98, 5.41, 6.83, and 7.19 respectively). The SEM and TEM images manifest that the average diameter of the PMo12/TiO2 composite fibers is about 130 ± 30 nm, and the average size of Ag NPs is about 15 ± 5 nm. Photocatalytic experiments confirm that PMo12/TiO2/Ag catalysts display highly efficient and durable activity for the photodegradation of methyl orange (MO) and photoreduction of Cr(VI) under visible light irradiation (λ > 420 nm). In these composite series, PMo12/TiO2/Ag-5.41 exhibits the highest photocatalytic activity. The photocatalytic mechanism reveals that both Ag and PMo12 can be excited under visible light irradiation, which greatly improves the visible-light absorption of the composites. Furthermore, the introduction of POM species can not only improve the light adsorption and redox activity of the TiO2, but also promote the photochemical stability of the plasmonic composites because of the relatively narrow band gap and low reversible redox potential of polyoxoanion. Such POMs-based plasmon photocatalysts are important in ongoing efforts to designing and exploring of new photocatalytic materials with low cost, high efficiency, and durability.

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