Impact of hematite surface magnetic configurations and strain on O2 adsorption

Abstract

Iron oxides are abundant and inexpensive materials with promising potential for catalysis. However, the influence of their intrinsic magnetic properties on their catalytic activity is not well established. This study investigates the correlation of magnetic order to the catalytic activity of the α-Fe₂O₃ (0001) surface using the adsorption of molecular oxygen as a descriptor. Our findings reveal that the magnetic order strongly influences the O₂ adsorption, yielding lower binding energies for the antiferromagnetic (AFM) configurations and making them more inert than the ferromagnetic (FM) one. We find the origin of the higher reactivity of the FM configuration in its broader d-band and its delocalization of the charge, together with the larger surface magnetization, relative to the AFM ones. Adsorption on the FM surface results in a markedly higher charge transfer to O₂ than on the AFM surfaces. These results highlight the critical role of magnetic configurations in governing the adsorption and catalytic properties of α-Fe₂O₃ (0001) surfaces, providing valuable insights for designing and optimizing more efficient magnetic catalysts. We also investigated the adsorption energy as a function of biaxial strain, finding that compressive strain strengthens adsorption on both FM and AFM surfaces, with the FM surface gaining additional stability relative to the AFM surface under compressive strain.

Graphical abstract