The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP) have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

Heterogeneous photocatalysis continues to be an active area of research with focus on developing catalytic systems that can degrade toxic pollutants in the gas and aqueous phase, and split water to generate hydrogen and oxygen. In this review, the incorporation of silica phases in titanium dioxide based photocatalysts is reviewed.

Mesoporous TiO2 photocatalysts were prepared in ethanol media by using relatively green, template free sol-gel technique. A mild hydrothermal treatment procedure was employed to tune the pore sizes of the materials. Comprehensive techniques that include powder X-ray diffraction, diffuse reflectance spectroscopy, specific surface area analysis, electron microscopy, FT-IR, TGA, and ζ-potential measurements were used to characterize the titania materials. Porosity (pore size and pore volume) of the materials were found to be key factors for the variation in the rate of photocatalytic degradation of rhodamine B; in addition to specific surface area, and surface hydroxyl groups. An increase in porosity permits effective transport of the dye molecules resulting in an increase in the rate of the degradation in materials having larger pores. A detailed electrospray ionization-mass spectrometric (ESI-MS) study was carried out for selected materials to identify photodegraded intermediates and products formed during the degradation of rhodamine B. In addition, experiments were also carried out to understand the role of reactive oxygen species (ROS). In summary, this work provides a simple way to tune pore sizes without the use of any template and an insight into the influence of pore size for the photocatalytic degradation of rhodamine B.

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This study focuses on employing cuprous iodide (CuI) as a hole-transporting material (HTM) in fabricating highly efficient perovskite solar cells (PSCs). The PSCs were made in air with either CuI or 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) as HTMs. A simple and novel pressing method was employed for incorporating CuI powder layer between perovskite layer and Pt top-contact to fabricate devices with CuI, while spiro-OMeTAD was spin-coated between perovskite layer and thermally evaporated Au top-contact to fabricate devices with spiro-OMeTAD. Under illuminations of 100 mW/cm2 with an air mass (AM) 1.5 filter in air, the average short-circuit current density (JSC) of the CuI devices was over 24 mA/cm2, which is marginally higher than that of spiro-OMeTAD devices. Higher JSC of the CuI devices can be attributed to high hole-mobility of CuI that minimizes the electron-hole recombination. However, the average power conversion efficiency (PCE) of the CuI devices were lower than that of spiro-OMeTAD devices due to slightly lower open-circuit voltage (VOC) and fill factor (FF). This is probably due to surface roughness of CuI powder. However, optimized devices with solvent-free powder pressed CuI as HTM show a promising efficiency of over 8.0 % under illuminations of 1 sun (100 mW/cm2) with an air mass 1.5 filter in air, which is the highest among the reported efficiency values for PSCs fabricated in an open environment with CuI as HTM.