Structures of seven molybdenum surfaces and their coverage dependent hydrogen adsorption

Abstract

Systematic density functional theory calculations and ab initio atomistic thermodynamics were applied to investigate the stability of seven metallic Mo surfaces [(110), (211), (111), (321), (310), (210) (100)] and their coverage dependent hydrogen adsorption. Only dissociative hydrogen adsorption is favored on these surfaces up to more than one monolayer saturation coverage. The computed hydrogen desorption temperatures on Mo(100) at 500 K and on Mo(110) at 410 K are in agreement with the available temperature-programmed desorption results. Under the consideration of H₂ as the reduction reagent in Mo catalyst preparation, the computed surface morphology of Mo single crystal shows only exposed (110), (211) and (100) at high temperature; and the estimated surface proportion order of (110) > (211) > (100) agrees very well with the X-ray diffraction detected intensity order of (110) > (211) > (100). Surface reconstruction upon hydrogen adsorption has also been discussed.