Ozone Formation during Photocatalytic Oxidation of Nitric Oxides under UV Irradiation with the Use of Commercial TiO2 Photocatalytic Powders

Abstract

The application of photocatalytic materials has been intensively researched in recent decades. The process of nitric oxide (NO) oxidation during photocatalysis has been observed to result in the formation of nitric dioxide (NO2). This is a significant factor of the photocatalysis process, as NO2 is more toxic than NO. However, it has been reported that ozone (O3) is also formed during the photocatalytic reaction. This study analyzed the formation and oxidationof O3 during the photocatalytic oxidation of NO under ultraviolet irradiation using commercial photocatalytic powders: AEROXIDE® TiO2 P25 by Evonik, KRONOClean® 7050 by KRONOS®, and KRONOClean® 7000 by KRONOS®. An NO concentration of 100 ppb was assumed in laboratory tests based on the average nitric oxide concentrations recorded by the monitoring station in Warsaw. A mix flow-type reactor was applied in the study, and the appropriateness of its application was verified using a numerical model. The developed model assumed an empty reactor without a photocatalytic material, as well as a reactor with a photocatalytic material at its bottom to verify the gas flow in the chamber. The analysis of the air purification performance of photocatalytic powders indicated a significant reduction of NO and NOx and typical NO2 formation. However, no significant formation of O3 was observed. This observation was verified by the oxidation of pure ozone in the process of photocatalysis. The results indicated the oxidation of ozone concentration during the photocatalytic reaction, but self-decomposition of a significant amount of the gas.

The Potential Risk of Nanoparticulate Release from Photocatalytic Pavement Concrete Surface Due to a Simulated Abrasion Load—An Experimental Study

“…Two types of nanometric titanium dioxide were used in this study: TiO 2 (A)—K7000 (Leverkusen, Germany) and TiO 2 (B)—P25 (Shanghai, China), with properties in the powder state as described in [ 35 ]. The content of the individual crystalline phases, the size of the crystallites, and the specific surface area of the photocatalysts are presented in Table 3 .…”

Analysis of Photocatalytic Degradation of Phenol by Zinc Oxide Using Response Surface Methodology

“…It adsorbs a large fraction of UV radiation. [26,27,28,29,30] The morphology and/or chemistry of the catalyst, as well as the operating settings, can all be optimized to enhance removal efficiency. The efficiency of the photocatalytic degradation process depends on the concentration of pollutant and photocatalyst, time, airflow rate, etc.…”

“…ZnO photocatalyst has also been suggested as a suitable alternative to TiO 2 due to its strong oxidation ability, wide and direct band gap of 3.37 eV at room temperature, excellent piezoelectric effect, low cost, non‐toxicity, and high free‐exciton binding energy of 60 meV at room temperature. It adsorbs a large fraction of UV radiation [26,27,28,29,30] …”

Catalytic Oxidation Activity of NO over Mullite-Supported Amorphous Manganese Oxide Catalyst

“…Nitric oxide (NO) is produced during high-temperature fossil-fuel combustion and leads to photochemical smog, acid rain, and ozone depletion, all of which are severely harmful to the environment and human health [ 1 , 2 ]. Therefore, reducing NO emissions from fossil fuels is essential to address climate change concerns.…”