(709e) Modeling Carbide-Derived Carbons with Reaxff

Carbide-derived carbons (CDCs) are a class of amorphous nanoporous carbons with high specific surface area and narrow pore size distribution on the order of  1 nm.  CDCs are becoming increasingly important for energy-related applications, such as gas storage, batteries, and supercapacitors1. In order to use molecular simulation to examine the molecular-level phenomena associated with these applications (e.g., the structure and behavior of ionic-liquid-based CDC supercapacitors), a realistic model of the CDC structure (or structures) is required. Palmer, et. al.2 have proposed a CDC model based upon quenching carbon from high to low temperature; however, the carbon forcefield used in this model used does not realistically reproduce the energy scale associated with bond formation and has not been derived to model metallic-carbon bonding typical of CDC precursors, which will limit the type of CDCs that can be derived1. Here, we investigate the use the use of the ReaxFF3 reactive forcefield to model CDC formation. ReaxFF provides a more realistic representation of the carbon and metallic bonding, allowing simulation to better mimic experimental processes used to form CDCs. As a validation of the ReaxFF forcefield, a temperature quench procedure similar to Palmer and coworkers is used to form CDCs, where the effect of quench rate is investigated. The radial distribution function, ring and pore size distribution, and adsorption are measured, where it is found that model structures generated via ReaxFF exhibit structural characteristics and physical properties consistent with those reported in experiment. Structural features are validated against through small-angle X-ray scattering (SAXS), adsorptive behavior of nitrogen, and pore size distributions are estimated from both techniques. Additionally, electrochemical properties are considered through the study of an electrochemical double layer with ionic liquid electrolytes.