Boosting hydroxyl radical production via floatable S-scheme hetejunction integrated polyacrylic acid hydrogels as photo-self-Fenton catalyst for pollutant removal

The non-homogeneous photocatalysis-self-Fenton technology represents a highly effective strategy for the degradation of pollutants. However, conventional catalysts are hindered by limitations such as restricted light absorption and challenges in separation. In this study, BaFe12O19 (BFO) was combined with iron-carbon dots modified resorcinol-formaldehyde (FRF) to construct an S-scheme heterojunction (BFR), which was subsequently incorporated into a cross-linked polyacrylic acid-base hydrogel (PAM) matrix to fabricate a floating composite gel catalyst. Under visible light irradiation, this catalyst achieved complete degradation of 20 mg/L chloroquine phosphate within 30 minutes, exhibiting a reaction rate constant 10 times greater than that of the BFR powder catalyst. The rate of in-situ generated H2O2 (30.05 mmol g−1 h−1) also increased by 11 times, that promoting the production of hydroxyl radicals (•OH). This significant improvement can be attributed to enhanced adsorption capacity of PAM hydrogel (124.2 mg g-1), superior near-infrared absorption, and photothermal effects of BFR heterojunction. The underlying mechanisms, including the formation of internal electric fields between FRF and BFO and the construction of the S-scheme heterojunction, were elucidated using in situ XPS and Kelvin probe force microscopy. Additionally, the analysis of reactive species, with potential degradation pathways for chloroquine phosphate (CQ), while toxicity assessments of the degradation products were conducted. This design of a floating photocatalyst provides an innovative approach to the development of efficient and recyclable photo-self-Fenton systems.