Hydrogen Adsorption and Site-Selective Reduction of the Fe3O4(001) Surface: Insights From First Principles

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• 作者：Narasimham Mulakaluri ; Rossitza Pentcheva
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：August 9, 2012
• 年：2012
• 卷：116
• 期：31
• 页码：16447-16453
• 全文大小：493K
• 年卷期：v.116,no.31(August 9, 2012)
• ISSN：1932-7455

文摘

Density functional theory calculations including an on-site Hubbard term are used to explore hydrogen adsorption on the surface of Fe₃O₄(001). The adsorption energy exhibits a minimum for two hydrogen atoms per (鈭? 脳 鈭?)R45掳 surface unit cell and gets less favorable with increasing hydrogen coverage due to OH鈥揙H repulsion. Terminations with two and four hydrogen atoms per surface unit cell are stable for moderate to high partial pressures of O and H. The strong tilt of the OH bond parallel to the surface facilitates hydrogen bonding to neighboring oxygen and hopping of the protons between surface oxygen sites. Furthermore, the formation of surface OH groups leads to a monotonic reduction of work function with increasing H coverage. The analysis of the electronic properties reveals selective switching of neighboring surface and subsurface Fe from Fe³⁺ to Fe²⁺ upon hydrogen adsorption. This provides a promising way to tune the catalytic activity of the Fe₃O₄(001) surface.