Efficient persulfate activation by hematite nanocrystals for degradation of organic pollutants under visible light irradiation: Facet-dependent catalytic performance and degradation mechanism

Hematite has been well studied in advanced oxidant processes (AOPs) due to its abundance and non-toxicity, but its precise mechanism in persulfate (PS) activation remains unclear. Here, we studied PS activation by hematite nanoplates (NPs) with dominant {001} facets, nanocubes (NCs) with dominant {012} facets, and nanorods (NRs) with dominant {110} facets, disclosing the facet-dependent PS activation for efficient degradation of organic pollutants over hematite crystals under visible light irradiation. Hematite NPs exhibited much higher oxidation degradation of organic pollutants than NCs and NRs. Density functional theory (DFT) calculation confirms that PS was more easily adsorbed by NPs than by NCs and NRs, which favored more PS-Fe(Ⅲ) complexes on the surface of hematite NPs. More reduced Fe(II) species from NPs than from others under visible light irradiation promoted PS activation, producing radicals for pollutants oxidation. These findings highlight the structure-performance relationship of irradiated hematite and the mechanisms in contaminant degradation.