Schuit Institute of Catalysis, Eindhoven University of Technology, Eindhoven, The Netherlands.
Chemphyschem. 2012 Apr 23;13(6):1583-90. doi: 10.1002/cphc.201100732. Epub 2012 Feb 1.
The formation of water by hydrogenation of atomic oxygen is studied using density functional theory. Atomic oxygen preferentially adsorbs at the four-fold hollow site, the hydroxyl group prefers the bridge site in a tilted configuration, and water is most stable when adsorbed at the top site with the two O-H bonds parallel to the Fe surface. Water formation by the hydrogenation of oxygen is a highly activated process on the Fe(100) surface, with similar activation energies, in the order of 1.1 eV, for the first and second hydrogen additions. A more favourable route for the addition of the second hydrogen atom involves the disproportionation of hydroxyl groups to form water and adsorbed oxygen. Dissociation of the OH is also likely since the activation energy is similar to that for disproportionation of 0.65 eV. Furthermore, the results show that the dissociation of water on Fe(100) is a non-activated process: 0.16 eV for the zero-coverage limit and 0.03 eV when surface oxygen is present. Herein, adsorption energies, structures and vibrational frequencies are presented for several adsorption states at 0.25 ML coverage, as well as the potential energy surface for water formation on Fe(100).
使用密度泛函理论研究了原子氧氢化生成水的过程。原子氧优先在四面体形的空位吸附，羟基在倾斜构象的桥位上优先吸附，而当水以两个 O-H 键与 Fe 表面平行的顶位吸附时最为稳定。在 Fe(100)表面上，氧的氢化生成水是一个高度活化的过程，第一个和第二个氢原子的添加具有相似的活化能，约为 1.1 eV。对于第二个氢原子的添加，更有利的途径涉及到羟基的歧化反应，生成水和吸附氧。由于 OH 的离解的活化能与歧化反应的活化能相似（0.65 eV），因此 OH 的离解也是可能的。此外，结果表明，Fe(100)上的水离解是一个非活化过程：在零覆盖极限下为 0.16 eV，当表面氧存在时为 0.03 eV。在此，给出了在 0.25 ML 覆盖率下几个吸附态的吸附能、结构和振动频率，以及 Fe(100)上生成水的势能面。
