Organic carbon modified Fe3O4/schwertmannite for heterogeneous Fenton reaction featuring synergistic in-situ H2O2 generation and activation

• In-situ H 2 O 2 generated by Fe 3 O 4 /Sch/C-driven O 2 reduction at a wide pH (3–9). • The carbon-modification promoted the selectivity of 2e − oxygen reduction reaction. • Fe 3 O 4 /Sch/C exhibited high reactivity (~81%) and H 2 O 2 selectivity (~65%). • Mechanisms of H 2 O 2 generation and degradation pathways of MB were proposed. Spontaneous generation of H 2 O 2 and activation in heterogeneous Fenton is a promising technology for waste-water treatment. Here organic carbon modified Fe 3 O 4 /schwertmannite (Fe 3 O 4 /Sch/OC) by introducing Fe 3 O 4 in the Acidithiobacillus ferrooxidans -driven Fe 2+ oxidation process to give catalysts. In-situ H 2 O 2 could be generated via Fe 3 O 4 /Sch/OC-driven oxygen reduction reaction (ORR), moreover, the in-situ H 2 O 2 was disintegrated to produce •OH in Fe 3 O 4 /Sch/OC-driven Fenton reaction to degrade the methylene blue (MB). The catalysts were characterized by XRD, SEM, BET and XPS spectroscopy. Oxygen-containing functional groups (e.g., C = O, –COOH, –OH) on Fe 3 O 4 /Sch/OC surface could provide more active sites for the adsorption and reduction of O 2 . The carbon-modification promoted both the selectivity of 2e − ORR and Fe 2+ content of catalyst. Thus, Fe 3 O 4 /Sch/OC exhibited a higher H 2 O 2 selectivity (~65%) and MB degradation efficiency (~81%) than Sch, Fe 3 O 4 , or Fe 3 O 4 /Sch. In addition, in-situ H 2 O 2 could be produced at a wide initial pH range (3–9). The degradation pathways of MB were also proposed based on theoretically calculated and LC-MS data. The finding opens up a new way for developing a cost-effective Sch-based catalyst for producing in-situ H 2 O 2 and degrading pollutants.