Study of solid/gas phase photocatalytic reactions by electron ionization mass spectrometry

Photocatalytic Lime Render for Indoor and Outdoor Air Quality Improvement

This article reports a novel photocatalytic lime render for indoor and outdoor air quality improvement that is composed of a lime binder and doped TiO2 (KRONOClean 7000®) nanoparticles. These nanoparticles were distributed throughout the bulk of the finishing render, instead of as a thin coating, thus ensuring the durability of the photocatalytic properties upon superficial damage. The physical properties of these renders were not affected by the addition of nanoparticles except in the case of surface area, which increased significantly. In terms of their photocatalytic activity, these novel lime renders were shown to degrade up to 12% NOx under UV light and up to 11% formaldehyde under visible light.

NOx-Reduction Performance Test for TiO2 Paint

In South Korea, the gradual increase in particulate matter generation has received significant attention from central and local governments. Exhaust gas, which contains nitrogen oxides (NO_x), is one of the main sources of particulate matter. In this study, the reduction of NO_x using a coating material mixed with a titanium dioxide (TiO₂) photocatalyst was demonstrated. The NO_x reduction performance of the TiO₂ photocatalyst-infused coating was evaluated by applying the ISO 22197-1: 2007 standard. Subsequently, the performance was evaluated by changing the NO gas concentration and ultraviolet (UV)-A irradiance under standard experimental conditions. It was determined that NO_x reduction can be achieved even if the NO gas concentration and UV-A irradiance are lower than those under the standard conditions when the TiO₂ photocatalyst-infused coating was used. This study revealed that NO_x reduction can be realized through TiO₂ photocatalyst-infused coating in winter or cloudy days with a low solar altitude. It was also confirmed that compared with the UV-A irradiance, the NO gas concentration has a greater effect on the NO_x reduction performance of the TiO₂ photocatalyst-infused coating. These findings can be used to evaluate a variety of construction materials with TiO₂ photocatalysts in the future.

Photocatalysis for Air Treatment Processes: Current Technologies and Future Applications for the Removal of Organic Pollutants and Viruses

Photocatalysis for air treatment or photocatalytic oxidation (PCO) is a relatively new technology which requires titanium dioxide (TiO2) and a source of light (Visible or near-UV) to degrade pollutants contained in air streams. Present approaches for the photodegradation of indoor pollutants in air streams aim to eliminate volatile organic compounds (VOCs) and viruses, which are both toxic and harmful to human health. Photocatalysis for air treatment is an inexpensive and innovative green process. Additionally, it is a technology with a reduced environmental footprint when compared to other conventional air treatments which demand significant energy, require the disposal of used materials, and release CO2 and other greenhouse gases to the environment. This review discusses the most current and relevant information on photocatalysis for air treatment. This article also provides a critical review of (1) the most commonly used TiO2-based semiconductors, (2) the experimental syntheses and the various photocatalytic organic species degradation conversions, (3) the developed kinetics and computational fluid dynamics (CFD) and (4) the proposed Quantum Yields (QYs) and Photocatalytic Thermodynamic Efficiency Factors (PTEFs). Furthermore, this article contains important information on significant factors affecting the photocatalytic degradation of organic pollutants, such as reactor designs and type of photoreactor irradiation. Overall, this review describes state-of-the-art photocatalysis for air treatment to eliminate harmful indoor organic molecules, reviewing as well the potential applications for the inactivation of SARS-CoV2 (COVID-19) viruses.

Solid-Gas Phase Photo-Catalytic Behaviour of Rutile and TiOn (1 < n < 2) Sub-Oxide Phases for Self-Cleaning Applications

The solid-gas phase photo-catalytic activities of rutile TiO₂ and TiO_n (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti³⁺ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti³⁺ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti³⁺-Ti⁴⁺ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO₂ and CO₂ under UV irradiation of wavelengths (λ) 376–387 nm and 381–392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350–400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO₂. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings.