Formation of Titania-Silica Mixed Oxides in Solvent Mixtures and Their Influences for the Photocatalytic CO2 Conversion to Hydrocarbon

TiO2-SiO2 mixed oxide photocatalyst materials responsive to simulated solar light illumination have been synthesized by sol-gel method in various polar and nonpolar organic solvent mixtures. The photocatalysts were characterized by numerous experimental techniques and investigated for the photocatalytic conversion of CO2 to CH4. The TiO2-SiO2 mixed oxide photocatalysts prepared in the presence of nonpolar aromatic solvents such as xylene, toluene or benzene along with ethanol show high surface area, huge mesoporosity and enormous pore volume compared to the materials conventionally synthesized in a mixture of ethanol and hexane. The TiO2-SiO2 mixed oxide photocatalyst prepared in benzene along with ethanol yields 21.0 ppm g-1 h-1 of methane production; however the material synthesized in hexane shows negligible amount of methane production under simulated solar light irradiation. These results indicate that aromatic nonpolar solvents can tune the textural properties of photocatalysts compared to non-polar aliphatic solvents. Copyright © 2015 American Scientific Publishers All rights reserved.

Photocatalytic conversion of CO2 to hydrocarbon fuel using carbon and nitrogen co-doped sodium titanate nanotubes

Carbon and nitrogen co-doped sodium titanate nanotubes (C,N-TNT) active under simulated solar light are synthesized by a simple two-step process comprising an alkaline hydrothermal technique followed by calcination. Different samples of C,N-TNT with varied dopant concentrations are achieved by changing the amount of urea as a nitrogen and carbon dopants. The photocatalysts are characterized using numerous experimental techniques, and under simulated solar light investigated for the photocatalytic conversion of CO<inf>2</inf> and water vapor to CH<inf>4</inf>. The C,N-TNT sample with an intermediate doping concentration yields the maximum methane yield of 9.75 μmol/g h. The key factors contributing in the improvement of photocatalyst performance includes light absorption, surface area and Na+ ions concentration in TNT acting as CO<inf>2</inf> adsorption site and photogenerated electrons recombination centers. The higher doping levels results in lower specific surface areas leading to decrease in photocatalyst performance. Our results suggest co-doping of nanostructured photocatalysts is an excellent pathway for improving textural and photocatalytic properties for the respective application domain. © 2015 Elsevier B.V. All rights reserved.

Novel Applications and Future Perspectives of Nanocomposites

As the present chapter of the book is located in the concluding section, it was important to highlight the main applications of composite materials focusing especially on applications, which exploit other peculiarities of the materials besides photocatalysis. This will be done, by introducing those materials and their composites that are most studied, or were found to exhibit interesting behavior. In many of the presented cases, the main structural, morphological, or optical property of the given composite will be discussed to understand its functioning mechanism, and its role in the current scientific approaches. Additionally, this chapter aims to give a perspective regarding the composite-based nanoscience, and points out important research directions for the further developments of composite materials