Hydrogen Adsorption Structures and Energetics on Iron Surfaces at High Coverage

Hydrogen adsorption structures and energetics on the (100), (110), (111), (210), (211), (310), and (321) iron surfaces up to saturation have been computed using spin-polarized density functional theory and ab initio thermodynamics. The computed hydrogen desorption temperatures and energies on the (100), (110), (111), and (211) surfaces as well as the Fe-H binding energies on the (110) and (111) surfaces agree well with the available experimental data. At typical hydrogen reduction temperature (675 K), the mainly exposed (110) and (310) facets represent the active surfaces, as supported by the transmission electron microscopy study. Our results offer an example of investigating and understanding surface structures and active facets of heterogeneous catalysts under experimental conditions.