AUTHOR=Wang Hongyu , Chang Xiaoya , Chen Dongping TITLE=Surface Reactivity of Carbonaceous Nanoparticles: The Importance of Surface Pocket JOURNAL=Frontiers in Mechanical Engineering VOLUME=7 YEAR=2021 URL=https://www.frontiersin.org/journals/mechanical-engineering/articles/10.3389/fmech.2021.738354 DOI=10.3389/fmech.2021.738354 ISSN=2297-3079 ABSTRACT=
The surface reactivity of carbonaceous nanoparticles is revealed from the barrier height and reaction enthalpy of hydrogen abstraction reaction by H radicals computed at the M06-2X/6–311g(d,p)//B3LYP/6-311G(d,p) level of theory. Small polycyclic aromatic hydrocarbon (PAH) clusters are selected as the model system of carbonaceous nanoparticles. The PAHs considered are naphthalene, pyrene, coronene, ovalene and circumcoronene. Cluster sizes range from dimer to tetramer with a parallel or crossed configuration. All results show similar values as that of monomers, but naphthalene dimers with a crossed configuration yield a lower barrier height and reaction enthalpy by ∼2 kcal/mol. A minor size dependence is noticed in the series of naphthalene clusters where a larger cluster exhibits a smaller barrier height. Larger homogeneous PAH clusters in a size range of 1.1–1.9 nm are later generated to mimic nascent soot surface. It is found that the barrier height decreases with the increase in particle size, and the averaged values are ∼2 kcal/mol lower than that of monomers. More importantly, a larger particle shows a wider spread in barrier heights, and low barrier heights are seen in the surface shallow regions (