TiO2-based catalytic systems for the treatment of airborne aromatic hydrocarbons.

Among diverse strategies to manage air quality, catalytic oxidation has been a widely used option to mitigate diverse pollutants such as aromatic volatile organic compounds (VOCs), especially benzene, toluene, and xylene (BTX). For such applications, TiO2-based catalysts have drawn significant research attention for their prominent photo/thermal catalytic activities and photochemical stability. This review has been organized to elaborate on the recent developments achieved in the thermocatalytic, photocatalytic, and photothermal applications of metal/non-metal doped TiO2 catalysts towards BTX vapors and their reaction mechanisms. The performance of the reported TiO2-based catalysts has also been analyzed based on multiple computational metrics such as reaction rate (r), quantum yield (QY), space-time yield, and figure of merit (FOM). At last, the research gap and prospects in the catalytic treatment of BTX are also discussed in association with the feasibility and utility of TiO2-based catalysts in air purification applications.

Photocatalytic degradation of gaseous benzene using metal oxide nanocomposites.

Rapid industrial growth has been accompanied by the pollution of hazardous volatile organic pollutants (VOCs) in air. Among various options available for the treatment of VOCs, the use of metal oxide composites as photocatalysts has been adopted preferably due to their potential to induce the synergistic interactions between the metal nanoparticles (NPs) and metal oxides (especially titanium dioxide (TiO2)). In this context, an in-depth review is offered to describe the fundamental mechanism of metal oxide-based photocatalysis for the oxidation of gaseous benzene as a model VOC. The discussion has been extended further to evaluate their performances in terms of key performance metrics (e.g., quantum yield (QY), space-time yield (STY), and figure of merit (FOM)). The TiO2-based metallic bi-component photocatalysts (e.g., Sr2CeO4/TiO2) generally exhibited better photodegradation efficiency with enhanced light absorption capability than monometallic-TiO2 (e.g., Pd-TiO2) composites or other modified photocatalysts (e.g., metal-organic framework (MOF)-based composites). Finally, we address the current challenges and future perspectives in this highly challenging research field.

Morphology Dependent Photocatalytic Activity of CuO/CuO-TiO2 Nanocatalyst for Degradation of Methyl Orange Under Sunlight.

CuO nanoparticles have been extensively used as a photocatalyst because of their superior activity, selectivity and stability properties. The catalytic efficiency of these oxide nanoparticles can be improved by varying the size and shape of nanoparticles. Here, we report the synthesis of different shaped CuO nanoparticles and their impregnation on TiO2. Optical analysis revealed that a considerable red shift (420 nm to 550 nm) in absorption spectra of CuO-TiO2 nanocomposites was observed compared to bare CuO nanoparticles. DLS measurements showed that the average hydrodynamic size of CuO nanostars was increased from 160 nm to 584 nm after deposition on TiO2. These nanocomposites were examined for photocatalytic degradation of methyl orange under sunlight radiation. It was observed that CuO-TiO2 nanostars exhibited superior photocatalytic efficiency compared to CuO-nanoneedles, nanocrumbles and bare CuO nanoparticles. The CuO nanoparticles act as co-catalyst on the surface of TiO2 and alter the physicochemical properties of TiO2. The higher activity arises due to the fact that the doping of CuO reduces the recombination of charge carries (e--h+) and creates the intra-gap states which result in higher absorption of light radiations. Therefore, CuO nanoparticles impregnated on TiO2 found to be an effective and ideal catalyst for the photodegradation of methyl orange dye.