Improvement of the Visible‐Light Photocatalytic Performance of TiO₂ by Carbon Mesostructures

Abstract

An improvement in the photodegradation performance for dyes due to interaction between carbon and titania in a self-assembled mesoporous C-TiO(2) composite catalyst, even for the difficult degradation of azo dyes, is reported herein. The dye removal process involves adsorption of the dye from water by the mesoporous carbon-titania, followed by photodegradation on the separated dye-loaded solid. Such adsorption-catalysis cycles can be carried out more than 80 times without discernible loss of photocatalytic activity or the anatase content of the composite. In each run, about 120 mg dye per g catalyst can be degraded. The mesoporous carbon-titania catalyst also exhibits a high capacity for converting methyl orange in aqueous solution under visible light. Characterization by XRD, TEM, and N(2) sorption techniques has revealed that the self-assembled composite catalyst has an ordered mesostructure, uniform mesopores (4.3 nm), a large pore volume (0.30 cm(3) g(-1)), and a high surface area (348 m(2) g(-1)). The pore walls are composed of amorphous carbon and anatase nanoparticles of size 4.2 nm, which are well dispersed and confined. X-ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), and UV/Vis absorption results indicate doping of carbon into the anatase lattice and a change in the bandgap of the semiconductor. The synergistic improvement in the composite catalyst can be attributed to the following features: (1) carbon doping of the anatase lattice modifies its bandgap and enhances its activity under visible light; (2) confinement within carbon pore walls prevents aggregation of tiny anatase nanoparticles, improving their activity and stability; (3) the mesopores provide a confined space for photocatalysis; and (4) the strong adsorption ability of porous carbon for organic substances ensures that large quantities can be processed and inhibits further diffusion of the adsorbed organic substances, thereby enhancing the mineralization on anatase.

Carbon coated Au/TiO2 mesoporous microspheres: a novel selective photocatalyst

“…As shown in Fig. 7, the adsorption capacity of the Au/TiO2@C-MMs decreased in the second cycle [12], and after that, the adsorption capacity and photocatalytic activity remained almost unchanged (91% after 6 cycles). This suggests that the Au/TiO2@C-MMs are quite stable during the adsorption and photocatalytic process.…”

“…Titania (TiO2) has been regarded as one of the most efficient photocatalysts since the first report by Fujishima and Honda [3][4][5][6], because of its high catalytic activity, good stability and low toxicity. After that, huge progress towards improving the photocatalytic efficiency of TiO2 has been made [7], such as band-tailoring by element doping [8,9], constructing mesoporous and/or array structures [10][11][12][13], and plasmonic sensitizing [14,15]. Nevertheless, TiO2 is generally regarded as non-selective because the degradation of organic compounds on TiO2 is enabled by nonselective oxidizing agents (e.g., OH radical) [16].…”

Atomically homogeneous dispersed ZnO/N-doped nanoporous carbon composites with enhanced CO2 uptake capacities and high efficient organic pollutants removal from water

“…11, the MB removal efficiency was remain high and still higher than 95% after six consecutive runs, suggesting a 29 good stability and reusability for the ZnO/C-S-S materials. It is likely that the physical walls of the porous carbon provide a confined space for photocatalysis, [15] which can prevent the aggregation of ZnO nanoparticles, maintain the high dispersibility of ZnO particles in porous carbon matrix, therefore the composite materials can keep the high adsorption and degradation activity and enhance the stability for MB removal from water. …”

“…[12,13] In addition, removal of organic pollutants from industrial and household wastewater is also an important environment issue and carbon-semiconductor composites have been explored for organic pollutants removal from wastewater. [14][15][16][17] For example, porous carbon-TiO 2 composite acts not only as a photocatalyst under visible light and showed good photodegradation activity for organic pollutants, but also as an adsorbent to extract the pollutants through the pores of the matrix. [14][15][16] Similarly, porous carbon-doped ZnO composite also exhibited a good photocatalytic performance in terms of the degradation of organic pollutants under visible light.…”

“…[14][15][16][17] For example, porous carbon-TiO 2 composite acts not only as a photocatalyst under visible light and showed good photodegradation activity for organic pollutants, but also as an adsorbent to extract the pollutants through the pores of the matrix. [14][15][16] Similarly, porous carbon-doped ZnO composite also exhibited a good photocatalytic performance in terms of the degradation of organic pollutants under visible light. [17,18] However, the components in these porous carbon-metal oxide composites usually cannot achieve homogeneous dispersion since they were frequently prepared by mechanical or physical mixing the metal oxides with the porous carbon materials.…”