On the mechanisms of heterogeneous catalysis by magnetic ferrite nanoparticles for H2O2 decomposition in reactive oxygen species

E. LIMA JR.; M.A. MORALES; N. NUÑEZ; T. TORRES MOLINA; M. VASQUEZ MANSILLA; D. TOBIA; M.E. SALETA; G.F. GOYA; R.D. ZYSLER; E.L. WINKLER

Puerto Varas

Congreso; XII Latin American Workshop on Magnetism and Magnetic Materials (LAW3M2023); 2023

Universidad Central

In specific conditions, the magnetic ferrite nanoparticles act as a catalyst in advanced oxidative process due to Fenton-like reaction related to the cationic composition (…Fe2+ => Fe3+ => Fe2+…) and the crystalline structure that allows the efficient electron transfer. In addition, the nanoscale of the material results in an enhanced process because of the high surface area. The oxidative oxidation processes are the result of hydrogen peroxide decomposition in reactive oxygen species (free radicals based in oxygen) catalyzed by the magnetic ferrite nanoparticles. In general, the mechanisms considered in these chemical chainreactions are based on extrapolation of homogeneous reaction with considering the adsorption of H2O2 by the oxide surface. In a general and simplified way, the adsorbed H2O2 linked to superficial Fe ions reacts, taking or donating an electron from the cation, and suffering a decomposition in two different species: hydroxyl radical (○OH) when reacting with Fe2+ and the superpoxide radical (○O2- or the perihydroxyl ○OOH in acidic pH) when reacting with Fe3+ ions.In this model, the kinetic of reaction is mediated by the adsorption rate and by the kinetics of the decomposition of the different Fe-H2O2 adducts. However, recent works have shown that the crystallinity, coordination, composition, surface chemistry and transport properties of the whole particle play major roles in the kinetics of heterogeneous chain reaction of the H2O2 decomposition in reactive oxygen reaction catalyzed by magnetic ferrite nanoparticles. In this work, we present some results that reinforce the dependence of the kinetic of this catalytic reaction with different material properties beyond the Fe2+/Fe3+ and the surface/volume ratios, specifically the ion coordination, the transport properties, the superficial Fe availability and consequently the H2O2 adsorption.The production of free radicals by different and very-well characterized ferrite nanoparticles is studied by EPR, optical spectrophotometry and FTIR. These results indicate the need of a deeper understanding of the mechanisms acting in the heterogeneous catalytic reaction of magnetic Ferrite nanoparticles to produce free radicals from the H2O2 decomposition and models that expand this one based in an extrapolation of the homogeneous mechanism.