Emerging low-temperature catalytic air oxidation technologies: A review on mechanisms and applications

Low-temperature catalytic air oxidation (LTCAO) uses air or O₂ as the sole oxidant to drive the mineralization or detoxification of organic pollutants and the inactivation of pathogens at ambient-to-sub-boiling temperatures (<100°C), without external energy inputs such as light, electricity, or high heat. Based on the extent to which O₂ activation contributes to pollutant removal, LTCAO systems are classified into poor-O₂-effect and strong-O₂-effect pathways to summarize the apparent catalytic trends observed across LTCAO systems. In the former, degradation relies primarily on direct catalyst-pollutant electron transfer, with O₂ serving mainly as a terminal electron acceptor, whereas in the latter, reactive oxygen species generated by O₂ activation play the dominant role. LTCAO catalysts are summarized into three types: single-atom catalysts, crystalline metal-based catalysts, and carbonaceous catalysts. For each catalyst type, the active sites and strategies for enhancing catalytic activity are reviewed. Catalytic pathways based on ground-state electron transfer are summarized, along with several mechanistic hypotheses and corresponding characterization strategies proposed to test them. The influence of catalyst dosage, pH, coexisting ions, and reactor configuration on LTCAO efficiency is analyzed together with the underlying mechanisms.