In situ use of photocatalytically produced H2O2 for Fenton degradation of organic pollutants

Abstract

Recent years have seen increased research on green H₂O₂ production by photocatalysis. Though the H₂O₂ formation by photocatalysis is still at a dilute level, it is sufficient to degrade a given organic pollutant by a photo-Fenton process. The in situ Fenton process avoids the costs of H₂O₂ storage and transportation and uses it more efficiently. The present review is on the in situ Fenton use of the H₂O₂ formed by photocatalysis. Though this technique is called the in situ Fenton process, converting H₂O₂ to hydroxyl radicals (·OH) has, to date, always been achieved under light irradiation or photo-Fenton conditions. We do a thorough literature survey of the present status of such in situ Fenton reactions and classify them into three types based on the photocatalyst and the reaction system composition. The H₂O₂-producing photocatalyst is also the main player in the in situ Fenton generation of ·OH. Mechanism inputs are drawn from the latest photo-Fenton research to understand the in situ Fenton process better. The review ends by listing the future challenges and perspectives in this nascent area of research.