Efficient roxarsone degradation via in-situ H2O2 generation through 2e-ORR over a Pd-Fe2O3 catalyst system.

Despite its efficacy in mineralizing pollutants, the Fenton reaction's requirement for continuous H2O2 addition entails high cost and safety drawbacks. This paper focuses on "substituting iron-based materials for ferrous salts in the Fenton reaction while simultaneously accelerating the two-electron oxygen reduction reaction (2e-ORR) to boost H2O2 production". At normal temperature and pressure, H2 was adsorbed and activated on Pd0 sites to form H∗, which was transferred to the catalyst surface through the hydrogen spillover effect to form [H]. Finally, H2O2 is generated in situ via the 2e-ORR. The H2O2 was further decomposed at the iron site into ·OH, O2-·, 1O2, and Fe (II), facilitating the degradation of the target pollutant ROX. Within 120 min, the degradation rates of 50 mg L-1 roxarsone in the Pd-on-Fe2O3+H2 and Pd-in-Fe2O3+H2 reaction systems were 96.0% and 69.5%, respectively. The quenching experiments and electron spin resonance (ESR) analysis demonstrated that 1O2 plays a dominant role in the system. The degradation efficiency of roxarsone was affected by the catalyst dosing, initial pH, H2 flow rates, and initial concentration of roxarsone. Furthermore, excellent stability of the Pd-Fe2O3 system was confirmed over six consecutive cycling experiments.