(560hp) Coupling the Magnetic and Catalytic Properties of Fe3O4 Via Shape-Controlled Routes and Cr Doping
In this work, thermal decomposition is used to produce monodisperse, spherical, cubic and octahedral shaped, Fe(3-x)CrxO4 nanoparticles as a strategy to improve the activity of the iron oxide (Fe3O4) host nanoparticles via Cr+3 doping, while maintaining the magnetic properties of the host lattice. Cr+3 replaces Fe+3 in the octahedral sites of Fe3O4 inverse spinel structure at low doping concentrations (x < 15 mol%), and tetrahedral and octahedral sites are substituted at higher concentrations. Low doping concentration improves activity and redox performance due to coupling of the Fe+3/Fe+2 with Cr+2/Cr+3, and regeneration of Fe+2 on the surface. To confirm this regeneration effect and the site occupancy of Cr in Fe3O4, L-edge X-ray Absorption Spectra of Fe and Cr is collected as well as X-ray Photoelectron Spectroscopy (XPS), to determine the formation of oxygen vacancies and to probe the valence state of Cr and Fe. In addition, Cr doping changes the pore structure from mesopores to micropores, thereby increasing the surface area, demonstrated through BET measurements. Finally, magnetic properties are characterized via Superconducting Quantum Interference Device (SQUID) measurements to show how the saturation magnetization, and coercivity are preserved. Induction heating is characterized by determining the Specific Loss Power of these materials under various magnetic field strength.