Institut Charles Gerhardt Montpellier, CNRS (UMR 5253), Université Montpellier 2 and Ecole Nationale Supérieure de Chimie Montpellier, Montpellier, France.
Phys Chem Chem Phys. 2011 Mar 7;13(9):3748-57. doi: 10.1039/c0cp02205e. Epub 2010 Dec 21.
Molecular simulations are used to study the adsorption, structure, and dynamics of benzene at 298 K in atomistic models of ordered and disordered nanoporous carbons. The ordered porous carbon is a regular slit pore made up of graphene sheets. The disordered porous carbon is a structural model that reproduces the morphological (pore shape) and topological (pore connectivity) disorder of saccharose-based porous carbons. As expected for pores of a regular geometry, the filling occurs at well-defined pressures which are an increasing function of the pore width H. In contrast, in qualitative agreement with experimental data for activated carbon fibers, the filling of the disordered carbon is continuous and spans over a large pressure range. The structure and dynamics of benzene in the disordered carbon also strongly depart from that for the slit pore geometry. While benzene in the slit graphite nanopores exhibits significant layering, benzene in the disordered porous carbon exhibits a liquid-like structure very close to its bulk counterpart. Both the ordering and self-diffusivity of benzene in the graphite nanopores depend in a complex manner on the pore width. The dynamics is either slower or faster than its bulk counterpart; our data show that the self-diffusivity decreases as the number of confined layers n divided by the pore width H increases (except for very small pore sizes for which benzene crystallizes and is necessarily slower than the liquid phase). The dynamics of benzene in the disordered porous carbon is isotropic and is much slower than that for the graphite slit nanopores (even with the smallest slit nanopore considered in this work). The results above show that the adsorption, structure, and dynamics of benzene confined in disordered porous carbons cannot be described in simple terms using an ideal model such as the slit pore geometry.
分子模拟用于研究苯在 298K 下在有序和无序纳米多孔碳的原子模型中的吸附、结构和动力学。有序多孔碳是由石墨烯片组成的规则狭缝孔。无序多孔碳是一种结构模型，再现了基于蔗糖的多孔碳的形态（孔形状）和拓扑（孔连通性）无序。正如规则几何形状的孔所预期的那样，填充发生在定义明确的压力下，这些压力随着孔径 H 的增加而增加。相比之下，与活性炭纤维的实验数据定性一致，无序碳的填充是连续的，跨越了很大的压力范围。苯在无序碳中的结构和动力学也与狭缝孔几何形状有很大的不同。虽然苯在狭缝石墨纳米孔中表现出明显的分层，但苯在无序多孔碳中表现出非常接近其本体的液态结构。苯在石墨纳米孔中的有序和自扩散都以复杂的方式依赖于孔径。动力学要么比本体慢，要么比本体快；我们的数据表明，自扩散系数随着被限制层数 n 除以孔径 H 的增加而减小（除了孔径非常小的情况，其中苯结晶并且必然比液相慢）。无序多孔碳中苯的动力学是各向同性的，比石墨狭缝纳米孔中的动力学慢得多（即使考虑到这项工作中考虑的最小狭缝纳米孔）。上述结果表明，无序多孔碳中苯的吸附、结构和动力学不能简单地用理想模型（如狭缝孔几何形状）来描述。
