Molecular Simulation of Benzene Adsorption in Graphitic and Amorphous Carbon Slit Pores

Abstract

Atmospheric soot consists of fractal aggregates of spherical particles, which are made of ordered (graphitic) and disordered (amorphous) carbon. Condensation of polycyclic aromatic hydrocarbons (PAHs) on the surface of spherical particles and in the junctions between these particles induces morphological changes in soot aggregates. We studied the interactions of benzene molecules with graphitic and amorphous carbon slit pores, where benzene represented PAHs and slit pores represented the junctions between carbon spheres in a soot aggregate. We used Monte Carlo simulations in the grand canonical ensemble (GCMC) to calculate benzene adsorption isotherms and molecular dynamics simulations to analyze benzene fluid structure inside the pores. As expected, confinement in graphitic and amorphous carbon pores resulted in significantly different adsorption isotherms and the local structure of benzene in the pores. We also found that using two different force fields for benzene (all-atom OPLS and a nine-site united atom TraPPE, which takes into account the quadrupole moment of benzene) produced similar adsorption isotherms, but a different orientation of benzene molecules in the pores.

Structurally Tunable Graphitized Mesoporous Carbon for Enhancing the Accessibility and Durability of Cathode Pt‐Based Catalysts for Proton Exchange Membrane Fuel Cells

“…The transition state of Pt clusters and O 2 molecules adsorbed on graphitized carbon is shown in Figure a, while the theoretical model of amorphous carbon consisting of multiple disordered chains in Figure 7b was formed based on molecular dynamics simulations. [ 49 ] Figure 7c shows that the adsorption energies of O 2 molecules on graphitized porous carbon and amorphous porous carbon (E ad1 ‐O 2 , E ad2 ‐O 2 ) were 0.68 and 0.13 eV, while O 2 molecules were more likely to adsorb near the nanopore in the model of the graphitized carbon. The adsorption energies of Pt clusters on graphitized carbon and amorphous carbon (E ad1 ‐Pt, E ad2 ‐Pt) were 9.86 and 2.54 eV, respectively (Figure 7d).…”

“…The formation process of amorphous carbon was based on molecular dynamics simulation of the liquid quenching method, characterized by the simulation of the actual process of amorphous carbon formation in the flame. [ 49 ] Similar to combustion, during the simulation, amorphous carbon changed from a high‐temperature liquid state to a low‐temperature solid state. Under the regular system canonical ensemble, indicates that a particle with a defined number of particles (N), volume (V), and temperature (T), the total number of simulation steps was set to 10 000, and the running time of each step was 1 fs.…”