α-Fe2O3 mediated periodate activation for selective degradation of phenolic compounds via electron transfer pathway under visible irradiation

Periodate (PI)-photoactivated advanced oxidation process (AOP) has recently received increasing attention for the removal of micropollutants from water. However, periodate is mainly driven by high-energy ultraviolet light (UV) in most cases, and few studies have extended it to the visible range. Herein, we proposed a new PI visible light activation system employing α-Fe2O3 as catalyst. It is completely different from traditional PI-AOP based on hydroxyl radicals (•OH) and iodine radical (•IO3). The vis-α-Fe2O3/PI system can selectively degrade the phenolic compounds via non-radical pathway under the visible range. Notably, the designed system not only shows a well pH tolerance and environmental stability, but also exhibits a strong substrate-dependent reactivity. Both quenching experiments and electron paramagnetic resonance (EPR) experiments demonstrate that photogenerated holes are the main active species in this system. Moreover, a series of photoelectrochemical experiments reveal that PI can effectively inhibit the carrier recombination on the α-Fe2O3 surface, thereby improving the utilization of photogenerated charges and increasing the number of photogenerated holes, which effectively reacts with 4-CP through electron transfer way. In a word, this work proposes a cost-effective, green and mild mean to activate PI, and provides a facile way to solve the fatal shortcomings (i.e., inappropriate band edge position, rapid charge recombination and short hole diffusion length) of traditional iron oxide semiconductor photocatalysts.