An Easy-Made, Economical and Efficient Carbon-Doped Amorphous TiO₂ Photocatalyst Obtained by Microwave Assisted Synthesis for the Degradation of Rhodamine B

Abstract

The search for novel materials and the development of improved processes for water purification have attracted the interest of researchers worldwide and the use of titanium dioxide in photocatalytic processes for the degradation of organic pollutants contained in water has been one of the benchmarks. Compared to crystalline titanium dioxide (cTiO₂), the amorphous material has the advantages of having a higher adsorption capacity and being easier to dope with metal and non-metal elements. In this work, we take advantage of these two features to improve its photocatalytic properties in the degradation of Rhodamine B. The structural characterization by XRD analysis gives evidence of its amorphous nature and the SEM micrographs portray the disc morphology of 300 nm in diameter with heterogeneous grain boundaries. The degradation of Rhodamine B tests with the amorphous TiO₂ using visible light confirm its improved catalytic activity compared to that of a commercial product, Degussa P25, which is a well-known crystalline material.

Keywords: Triple-E photocatalyst; amorphous titanium oxide; microwave assisted synthesis.

Figure 1

X-ray diffractograms of all the obtained aTiO₂ and commercial DP25 products.

Figure 2

Scanning electron microscope (SEM) micrographs of all the CD-aTiO₂ prepared (a) DTIB-01; (b) DTIB-02; (c) DTIB-03; (d) DTIB-04; (e) DTIB-05; (f) the disc morphology with a dimension of ~300 nm in diameter of these products can be observed in the last pictured.

Figure 3

Transmission electron microscope (TEM) images of carbon-coated CD-aTiO₂ for the DTiB-04 photocatalyst, (a) particles conglomerates at 200 nm (see Figure 1b), (b) zoom of image (a) to 5 nm and (c,d) nanocrystals of image (b) to 2 nm.

Figure 4

(a) N₂ adsorption-desorption plot for the DTiB-04 isotherm; (b) Pore size distribution curve for the same DTiB-04 sample obtained from the desorption isotherm.

Figure 5

Fourier-transform infrared spectroscopy (FT-IR) spectra for all the CD-aTiO₂ synthetized and used in this work.

Figure 6

(a) Thermogravimetric (TG) and (b) differential scanning calorimetry (DSC) analysis for all the CD-aTiO₂ photocatalysts synthetized and used in this work.

Figure 7

Diffuse reflectance ultraviolet–visible spectroscopy (DRS UV-vis) spectra for all the CD-aTiO₂ samples prepared in this work and for the commercial DP25 TiO₂.

Figure 8

UV-Vis spectra of the final concentration of Rhodamine B after a 20 min adsorption process in the presence of all the photocatalysts.

Figure 9

Hypsochromic shift detected during the degradation process of Rhodamine B with (a) DTiB-01 and (b) DTiB-02.

Figure 10

UV-Vis spectra for the remaining Rhodamine B solutions after a 100 min exposure to visible light.

Figure 11

(a) Adsorption (in the dark) and degradation (during exposure to visible light) rates of Rhodamine B for all the obtained photocatalysts; (b) Adsorption and degradation rates for increasing concentrations of Rhodamine B using the same DTiB-04 photocatalyst.