Mulakaluri, Narasimham; Pentcheva, Rossitza (2012): Hydrogen Adsorption and Site-Selective Reduction of the Fe3O4(001) Surface: Insights From First Principles. In: Journal of Physical Chemistry C, Vol. 116, Nr. 31: S. 16447-16453
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Density functional theory calculations including an on-site Hubbard termare used to explore hydrogen adsorption on the surface of Fe3O4(001).The adsorption energy exhibits a minimum for two hydrogen atoms per(root 2 x root 2)R45 degrees surface unit cell and gets less favorablewith increasing hydrogen coverage due to OH-OH repulsion. Terminationswith two and four hydrogen atoms per surface unit cell are stable formoderate to high partial pressures of O and H. The strong tilt of the OHbond parallel to the surface facilitates hydrogen bonding to neighboringoxygen and hopping of the protons between surface oxygen sites.Furthermore, the formation of surface OH groups leads to a monotonicreduction of work function with increasing H coverage. The analysis ofthe electronic properties reveals selective switching of neighboringsurface and subsurface Fe from Fe3+ to Fe2+ upon hydrogen adsorption.This provides a promising way to tune the catalytic activity of theFe3O4(001) surface.