Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (02): 271-278.

• THEORETICAL AND COMPUTATIONAL CHEMISTRY •

### A Density Functional Theory Study of HF Adsorption on the α-AlF3(0001) Surface

LIU Rui, Teng Bo-Tao, QUAN Jie-Li, LANG Jia-Jian, Luo Meng-Fei

1. Institute of Physical Chemistry, Zhejiang Key Laboratory Chemistry on Solid Surfaces, Zhejiang Normal University, Jinhua 321004, Zhejiang Province, P. R. China
• Received:2012-09-13 Revised:2012-11-26 Published:2013-01-14
• Supported by:

The project was supported by the National Natural Science Foundation of China (20903081) and Natural Science Foundation of Zhejiang Province, China (Y407163).

Abstract:

Using density functional theory, the adsorption behaviors of HF at α-AlF3(0001) surfaces with different coverages of 3F, 2F, 1F, and Al terminations were studied systematically. The electronic interactions between HF and the α-AlF3(0001) surfaces were also analyzed. Our results indicated that physisorption occurs when HF adsorbs at the 3F-terminated surface. Strong chemisorption occurs, and Al-F and FHF structures form when HF adsorbs at surfaces with 2F and 1F terminations. Under these conditions, the HF molecule is activated, and might take part in the subsequent fluorination reactions. Dissociated adsorption occurs, and Al-F and Al-H bonds form when HF is adsorbed on the Al-terminated surface. The unsaturated coordination numbers for surface Al with 3F, 2F, 1F, and Al-terminated surfaces are 0, 1, 2, and 3, respectively. The coordination number of the AlF2 surface is saturated when one HF molecule adsorbs; then, only physical adsorption occurs for any subsequently adsorbed HF molecules. However, it can still chemisorb at the 1F and Al-terminated surfaces. It is therefore reasonable to deduce that the higher the unsaturated coordination number of the surface, the higher the amount of activated HF, and possibly the higher the catalytic activities in the fluorination reactions. Charge density difference and density of states indicated that weak interactions occur between the HF and the 3F-terminated surface, while strong interactions occur between the HF and the 2F, 1F, Al-terminated surfaces.

MSC2000:

• O641