Fabrication of Zn3(PO4)2/carbon nanotubes nanocomposite thin film via sol-gel drop coating method with enhanced photocatalytic activity

Abstract

Thin films of Zn3(PO4)2 and Zn3(PO4)2/carbon nanotubes (Zn3(PO4)2/CNT) were fabricated on glass substrate by the simple sol-gel drop coating method. The crystal structure, particle size, morphology and optical properties were characterized by X-ray Diffraction, Field Emission Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy (FT-IR) and Ultraviolet-visible Spectroscopy. The X-ray diffraction results revealed the formation of zinc phosphate crystal without any impurities as well as the average particle size of 24 nm and 19 nm for Zn3(PO4)2 and Zn3(PO4)2/CNT, respectively. FT-IR spectral data confirmed the grafting of the polar carboxylic and hydroxyl functional groups on the surface of nanotubes due to functionalization and also the presence of PO43- group. The formation of heterojunction interface between CNT and Zn3(PO4)2 reduce the fast recombination of charge carriers, which leads to the high photoenergy conversion efficiency. The as-synthesized Zn3(PO4)2/CNT composite thin film showed highest photocatalytic efficiency for the degradation of cationic organic dye methylene blue under ultraviolet (UV) (85%) and visible (53%) light irradiation. Incorporation of CNT with the Zn3(PO4)2 enhanced the photocatalytic efficiency two fold in case of UV and four fold higher in presence of visible light irradiation as high as bare Zn3(PO4)2. We offer that this work will smooth the progress of preparation of innovative phosphate based photocatalysts for degradation of organic pollutants from environment under UV light illumination. Furthermore, a plausible photocatalytic degradation mechanism of an organic pollutant by the synthesized Zn3(PO4)2/CNT composite is proposed.