Calculation of the Adsorption Isotherm of Formaldehyde on Ice by Grand Canonical Monte Carlo Simulation

详细信息    查看全文

• 作者：Gy&ouml ; rgy Hantal ; Pá ; l Jedlovszky ; Paul N. M. Hoang ; Sylvain Picaud
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：September 27, 2007
• 年：2007
• 卷：111
• 期：38
• 页码：14170 - 14178
• 全文大小：543K
• 年卷期：v.111,no.38(September 27, 2007)
• ISSN：1932-7455

文摘

The adsorption isotherm of formaldehyde at the surface of I_h ice has been calculated at 200 K by performinga set of grand canonical Monte Carlo simulations, systematically varying the chemical potential offormaldehyde. In a clear contrast to other partially oxidized small hydrocarbons (POHs), such as methanol,the obtained isotherm does not show any particular stability of the saturated adsorption monolayer of theformaldehyde molecules. Further, in contrast to that of methanol, the obtained adsorption isotherm can bewell described with the functional form of the Langmuir isotherm, indicating the relative weakness of thelateral interactions between the adsorbed molecules. The obtained results show that the main thermodynamicdriving force of the adsorption is the possibility of the formation of water-formaldehyde hydrogen bonds.However, an adsorbed formaldehyde molecule has never been found to form more than one hydrogen bondwith the surface waters, and due to the requirement of maximizing the number of water-formaldehyde hydrogenbonds per surface unit, these hydrogen bonds are often rather distorted, hence they are relatively weak in thecase of the saturated adsorption monolayer. Besides these water-formaldehyde hydrogen bonds, the adsorbedmolecules are further stabilized by lateral dipole-dipole type interactions, which are, however, considerablyweaker than the water-formaldehyde hydrogen bonds, and also weaker than the lateral hydrogen bondingthat occurs in the adsorption layer of other POH molecules, such as methanol.