Photocatalytic NO removal: complete oxidation and reduction reaction for by-product inhibition and end-product recovery

Abstract

Nitrogen oxides (NO_x, x = 1 and 2, the proportion of NO is about 95%), as one of the primary precursors for particulate matter and ozone, limit the continuous improvement of air quality. Photocatalytic NO purification technology has attracted significant attention, and much efforts have been devoted to realizing the complete photocatalytic oxidation and reduction of NO for toxic by-product inhibition and end-product recovery. This work presents a timely overview of the current research progress on the conversion of NO into nitrate/ammonia (NO₃⁻/NH₃), which can be further recycled and utilized. According to the principle of heterogeneous photocatalysis and considering the significance of the reaction microenvironment (surface active sites of photocatalysts, target pollutants and reaction media), this review systematically summarizes the progress on the strategies for controlling the surface structure of photocatalysts and reaction medium. Specifically, this critical overview is focused on various methods for the surface modification of photocatalysts, strategies to accelerate the mass transfer process of gaseous NO, and the effect of the additional introduction of a reductant/antioxidant in the reaction system. Furthermore, research trends and future prospects are discussed, aiming to provide insights into the breakthroughs and boost the development of photocatalytic NO removal technology.