Conducting polymer nanostructures for photocatalysis under visible light

Journal name:
Nature Materials
Volume:
14,
Pages:
505–511
Year published:
DOI:
doi:10.1038/nmat4220
Received
Accepted
Published online

Visible-light-responsive photocatalysts can directly harvest energy from solar light, offering a desirable way to solve energy and environment issues1. Here, we show that one-dimensional poly(diphenylbutadiyne) nanostructures synthesized by photopolymerization using a soft templating approach have high photocatalytic activity under visible light without the assistance of sacrificial reagents or precious metal co-catalysts. These polymer nanostructures are very stable even after repeated cycling. Transmission electron microscopy and nanoscale infrared characterizations reveal that the morphology and structure of the polymer nanostructures remain unchanged after many photocatalytic cycles. These stable and cheap polymer nanofibres are easy to process and can be reused without appreciable loss of activity. Our findings may help the development of semiconducting-based polymers for applications in self-cleaning surfaces, ​hydrogen generation and photovoltaics.

At a glance

Figures

  1. Synthesis and characterization of PDPB nanofibres.
    Figure 1: Synthesis and characterization of PDPB nanofibres.

    a, Photograph of swollen hexagonal phases before polymerization (transparent gel) and after polymerization (yellow gel) by ultraviolet irradiation. b, Schematic of polymerization of ​diphenylbutadiyne (​DPB) by ultraviolet irradiation. c, Small-angle X-ray scattering spectra of swollen hexagonal phases before (black squares) and after polymerization of ​1,4-diphenylbutadiyne by ultraviolet irradiation (red cycles). The diffraction patterns are characteristic of a hexagonal phase, as demonstrated by four Bragg peaks (black arrows) whose positions are in the ratio 1: 3:2: 7. From the peak position and sample composition, one evaluates that the diameter of the oil-swollen surfactant-stabilized tubes is 16 nm. Inset: scheme of an oil-swollen hexagonal phase. d, Absorption spectra of solid PDPB nanostructures. Inset: Solid powder of PDPB nanostructures. e, Transmission electron micrograph of PDPB nanostructures prepared by the soft templating approach. f, ATR–FTIR spectra of PDPB nanostructures synthesized by ultraviolet light irradiation. gi, AFM–infrared spectra recorded in three different spectral regions for PDPB. g, Inset: Atomic force micrograph of the PDPB nanostructure, with the local region of the polymer nanostructure used for the nanoIR spectra marked with a green star.

  2. Comparative photocatalytic activity of PDPB nanofibres, TiO2 and Ag–TiO2.
    Figure 2: Comparative photocatalytic activity of PDPB nanofibres, ​TiO2 and Ag–TiO2.

    ad, Photocatalytic degradation of ​methyl orange (a,b) and ​phenol (c,d) in the presence of commercial P25 TiO2, Ag–TiO2 and the synthesized bulk PDPB and nano PDPB. a,c, Degradation carried out under visible light (>450 nm). b,d, Degradation carried out under ultraviolet light. The concentrations of nano PDPB, bulk PDPB, Ag–TiO2 and ​TiO2 in water were 1 mg ml−1. Initial concentrations C0 were 6 × 10−5 mol l−1 for ​MO and 3.7 × 10−3 mol l−1 for ​phenol. The legend in a applies to all panels.

  3. Schematic representation of the photocatalytic mechanism and energy level calculation of polymer structures by density functional theory.
    Figure 3: Schematic representation of the photocatalytic mechanism and energy level calculation of polymer structures by density functional theory.

    a, Energy diagram representing the evaluated HOMO and LUMO levels of PDPB polymer. b, Possible photocatalysis mechanism with charge separation in nano PDPB, with electron reducing ​oxygen and hole oxidizing ​water; the holes and generated oxidative radicals can oxidize organic pollutants (noted as M), V.B. and C.B. represent the valence band and the conduction band of PDPB polymer, respectively.

  4. Recycling and stability of the PDPB nanofibres.
    Figure 4: Recycling and stability of the PDPB nanofibres.

    a, Photocatalytic degradation of ​MO and ​phenol after up to five cycles measured after visible light irradiation of duration 240 min. b, Topographic image of photosynthesized PDPB nanofibres by conventional AFM after degradation of ​methyl orange. c, NanoIR mappings of the PDPB nanostructures after photocatalytic degradation of ​methyl orange as measured at a fixed wavenumber (3,054 cm−1) after five cycles. The signal obtained at 3,054 cm−1 in chemical mapping, which originates from the ​benzene ring in the PDPB polymer, does not change after degradation. d,e, NanoIR spectra recorded in two different spectral regions of the PDPB nanofibres before and after catalysis. The large intensity change for the C–H stretching modes of the polymer nanostructure is associated with the frequency band at 3,054 cm−1. The intense band at 1,490 cm−1 is associated with the π-conjugated enyne unit as well as aromatic ring stretching and bending vibration of the ​benzene ring in the PDPB polymer. f, TEM image of the PDPB nanostructure after degradation of ​methyl orange under visible light irradiation.

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Author information

Affiliations

  1. Laboratoire de Chimie Physique, UMR 8000-CNRS, Bât. 349, Université Paris-Sud, 91405 Orsay, France

    • Srabanti Ghosh,
    • Natalie A. Kouamé,
    • Samy Remita,
    • Alexandre Dazzi,
    • Ariane Deniset-Besseau &
    • Hynd Remita
  2. Laboratoire Charles Coulomb (L2C) UMR 5221 CNRS-Université de Montpellier, 34095 Montpellier, France

    • Laurence Ramos
  3. Départment CASER, Ecole SITI, Conservatoire National des Arts et Métiers, CNAM, 292 rue Saint-Martin, 75141 Paris Cedex 03, France

    • Samy Remita
  4. Sorbonne Universités, UPMC Univ. Paris 06, UMR 7197-CNRS, Laboratoire de Réactivité de Surface, F-75005 Paris, France

    • Patricia Beaunier
  5. CNRS, UMR 7197, Laboratoire de Réactivité de Surface, F-75005 Paris, France

    • Patricia Beaunier
  6. Laboratoire de Physicochimie des Polymères et des Interfaces (LPPI), Université de Cergy-Pontoise, 95031 Cergy-Pontoise Cedex, France

    • Fabrice Goubard &
    • Pierre-Henri Aubert
  7. CNRS, Laboratoire de Chimie Physique, UMR 8000, 91405 Orsay, France

    • Hynd Remita

Contributions

S.G. carried out fabrication of the polymer nanostructure, performed the experiment on photocatalytic activity and also contributed to writing of the manuscript. N.A.K. conducted the photocatalysis experiments. L.R. characterized the doped mesophases by SAXS and the polymer by XRD. S.R. provided information about conducting polymers. A.D. and A.D-B. ran the nanoIR system for characterization and stability of the polymer nanostructures with cycling. P.B. characterized the polymer nanostructures by TEM. F.G. and P-H.A. provided NMR characterizations, theoretical calculations, bandgap measurements and electrochemical investigations. H.R. supervised the entire project and also wrote the manuscript.

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The authors declare no competing financial interests.

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