Considerations to improve adsorption and photocatalysis of low concentration air pollutants on TiO2

• Coexistent air components need to be taken into account for realistic assessment.
• Experimental conditions to reproduce realistic conditions such as short contact time and low pollutant concentrations.
• Progress in adsorption enhancement for improved photocatalytic removal of air pollutants is highlighted.
• A comparison between adsorbent supported catalyst versus a high-surface area porous photocatalyst is presented.

Rapid development of nanoscience and nanotechnology has greatly supported the industrialization of titanium dioxide for environmental pollution control during the past decade. Nowadays, low concentration air purification seems to be one of the most promising directions of environmental TiO2 applications. However, much more effort is needed to perfect this technology and make it broadly applicable. Understanding the nature of the adsorption and photooxidation under realistic and practical conditions would give clear guidance for the development of novel catalytic materials and technologies. This paper describes the significant effects of the adsorption of low concentration gas-phase pollutants in practical conditions on the photocatalytic oxidation efficiency and mechanism. We also review the influences of several important conditions, such as pollutant concentration, contact time, co-existing pollutants, water vapor, and light exposure, on the nature of the adsorption process and thereby the photooxidation. Finally, catalytic materials which might enhance the adsorption of low-concentration pollutants are summarized.

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