New Insights into the Mechanism of Visible Light Photocatalysis

ABSTRACT: In recent years, the area of developing visible-lightactive photocatalysts based on titanium dioxide has been enormously investigated due to its wide range of applications in energy and environment related fields. Various strategies have been designed to efficiently utilize the solar radiation and to enhance the efficiency of photocatalytic processes. Building on the fundamental strategies to improve the visible light activity of TiO2-based photocatalysts, this Perspective aims to give an insight into many contemporary developments in the field of visible-light-active photocatalysis. Various examples of advanced TiO2 composites have been discussed in relation to their visible light induced photoconversion efficiency, dynamics of electron− hole separation, and decomposition of organic and inorganic pollutants, which suggest the critical need for further development of these types of materials for energy conversion and environmental remediation purposes

Investigation on swelling behavior of sodium alginate/black titania nanocomposite hydrogels and effect of synthesis conditions on water uptake

Polymeric nanocomposite hydrogels were developed from a hydrophilic natural polymer, sodium alginate (SA) with black nano crystalline titania (black TiO2) by using ionic cross linker CaCl2, in view of the possible enhancement in properties of SA towards water treatment application. The optimum conditions for the preparation of films were done by varying the amount of cross-linking agent, cross-linking time and the amount of black nano crystalline TiO2. The nanocomposite hydrogels were then characterized by X-ray diffraction studies (XRD), fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The surface morphologies of the nanocomposite have been examined by using scanning electron microscopy (SEM). The swelling studies and its kinetics have been investigated under diverse PH conditions. Permeability of the gels were assessed in terms of film characteristics and PH. The results proved that the gels exhibit PH sensitivity. Based on the results, we have proposed a possible mechanism of water transport through the gels. The developed SA/black TiO2 nanocomposite hydrogels have been successfully employed for the efficient degradation organic dyes such as methylene blue and malachite green. The experimental results of dye degradation studies have been compared with theoretical models and it has been observed that the dye degradation follows pseudo second order kinetics for both methylene blue and malachite green. By altering the PH, the nanocomposite hydrogels can be broken and spent TiO2 can be recovered

Photo-electrodes decorated with carbon quantum dots: Efficient dye-sensitized solar cells

In this study, the blue and green carbon quantum dots (CQDs) are synthesized and applied to the photo-electrodes of dye-sensitized solar cells (DSSCs). The DSSCs exhibited high power conversion efficiency because of the conversion of ultraviolet to the visible region in photo-anode, and good catalytic activity in the photo-cathode. The blue color CQDs (BCQDs) and green color CQDs (GCQDs) are synthesized from the citric acid in a single pot process. We examine the influence of both CQDs decorated on photo-anode and photo-cathode and both photo-electrodes on the photovoltaic performance of the DSSCs. Furthermore, the DSSCs are studied by electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization data to study the charge transfer kinetics. The better performance observed from the DSSCs due to enhanced charge carrier collection through the CQDs. The photovoltaic results of DSSCs shown that the best efficiency shown by DSSC, which fabricated by both photo-electrodes decorated by CQDs