Design and mechanism of photocatalytic oxidation for the removal of air pollutants: a review

Nitric oxide, ammonia and volatile organic compounds are common air pollutants which need to be removed for health security. To reach ultra-low emission standards, photocatalysis has emerged as a environmentally benign and efficient method to lower pollutant levels. Understanding the pollutant removal mechanism is necessary to optimize the design of the photocatalyst. Here, we review air purification by gas–solid photooxidation. We discuss the role of light absorption, charge carrier separation and active sites for designing the photocatalyst. We present reaction processes with emphasis on the adsorption and activation of reactants, the formation of intermediates and byproducts, and the conversion pathways towards the final product. Perspectives of photocatalytic degradation in suppressing by-products, inhibiting deactivation and dealing with pollutant mixtures are discussed.