Advances in photocatalytic technologies for air remediation

Photocatalysis has emerged as one of the promising eco-friendly approaches for treating environmental pollutants, especially air purification, in the past decade because of a number of merits over its conventional counterparts, such as adsorption or filtration. Its advantages include the complete oxidization of organic pollutants to CO2 and H2O with the generation of little secondary organic pollutants, easy operating conditions suitable for integration in existing heating, ventilation, and air conditioning equipment, and the ability to work at ppb or ppm low concentration levels, which are the typical loading of polluted air in offices and buildings. However, the practical applications of photocatalysis have been hindered due to the low utilization of solar energy and rapid electron–hole recombination in photocatalysts. In this chapter the photocatalytic mechanism of gas treatment is firstly introduced, including hydrogen evolution, carbon dioxide reduction, carbon monoxide oxidation, and nitrogen oxide treatment. Then a detailed survey and discussion on applications and designs of TiO2-based photocatalysts are presented. The relationships between photocatalytic activities and catalyst properties are further discussed. This work will shed light on the innovative design of new photocatalytic materials for gas treatment.