Flexible Photocatalytic Paper with Cu2O and Ag Nanoparticle-Decorated ZnO Nanorods for Visible Light Photodegradation of Organic Dye

Abstract

We report on the fabrication of flexible photocatalytic paper comprised of Cu₂O and Ag nanoparticle (NP)-decorated ZnO nanorods (NRs) and its application in visible light photodegradation of organic dye. ZnO NRs are first grown on a kraft paper substrate using a hydrothermal method. The NRs are subsequently decorated with Cu₂O, Ag, or both NPs formed by photoreduction processes. Scanning electron microscopy and X-ray diffraction analysis confirm the crystallinity of ZnO NRs. Transmission electron microscopy analysis confirms the compositions of the two types of NPs. Four different types of photocatalytic papers with a size of 10 × 10 cm² are prepared and used to degrade a 10-μM and 100-mL rhodamine B solution. The paper with Cu₂O and Ag NP-co-decorated ZnO NRs has the best efficiency with first-order kinetic constants of 0.017 and 0.041 min^-1 under the illumination of a halogen lamp and direct sunlight, respectively. The performance of the photocatalytic paper compares well with other substrate-supported ZnO nanocomposite photocatalysts. With the advantages of flexibility, light weight, nontoxicity, low cost, and ease of fabrication, the photocatalytic paper has good potential for visible light photocatalysis.

Keywords: Ag nanoparticle; Cu2O nanoparticle; Photocatalysis; Photocatalytic paper; ZnO nanorod.

Fig. 1

a Photographs of a kraft paper substrate (left) and the paper with as-grown ZnO NRs (right). b SEM images of the ZnO NR paper. c–f SEM images of ZnO, Cu₂O/ZnO, Ag/ZnO, and Ag/Cu₂O/ZnO NRs, respectively

Fig. 2

a–c EDS spectra of the Cu₂O/ZnO, Ag/ZnO, and Ag/Cu₂O/ZnO NRs, respectively

Fig. 3

a A TEM image of an Ag/Cu₂O/ZnO NR. b, c High-resolution TEM images of a Cu₂O and an Ag NP, respectively. d, e Fourier transform patterns of the Cu₂O and the Ag NP, respectively

Fig. 4

a, b High-resolution TEM images of a Cu₂O NP and an Ag NP, respectively

Fig. 5

a, b X-ray diffraction patterns of as-grown ZnO and Cu₂O/ZnO NRs. c An XPS spectrum of Cu₂O/ZnO NRs

Fig. 6

PL spectra of the four photocatalytic papers

Fig. 7

a, b Absorption spectra of the RhB solution as a function of time (at a 10-min interval) resulting from the photocatalysis of the ZnO and the Ag/Cu₂O/ZnO papers, respectively. c Plots of ln(C_t/C₀) for the ZnO paper in the dark and the four photocatalytic papers under the light. d Plots of ln(C_t/C₀) for the Ag/Cu₂O/ZnO paper under the illumination of a halogen lamp and direct sunlight

Fig. 8

a–d SEM images of Ag/ZnO NRs with photoreduction times of 1, 1.5, 2, and 2.5 min, respectively

Fig. 9

The energy band diagrams of ZnO and Cu₂O and the standard reduction potentials for Eqs. (1) and (2). The reduction potential is relative to SHE, which is 4.44 eV below the vacuum level