Developing realistic molecular models of biochars

Biochars are widely studied porous materials with applications as economical alternatives to traditional adsorbents, but a molecular-level understanding of their structures is hampered by a lack of good computational models. In the first part one of this two-part study, we reviewed experimental methods used to characterize biochars and compiled a database of publicly available experimental data. Here, we present an iterative approach that allows building biochar molecular models, based upon their experimentally derived chemical descriptors (e.g., H/C and O/C ratios, functional groups, aromaticity index) and validated upon emerging physicochemical properties (e.g., true density and high-resolution transmission electron microscopy [HRTEM]). This approach allows us to build the first, to our knowledge, molecular models of biochar materials, representative of woody biochars produced across a broad range of pyrolysis temperatures: 400°C, 600°C, and high 800°C. To ensure the accessibility of these models for use by the broad research community, we share these models, assigned with the OPLS-AA force field and setup for simulations with GROMACS.