Atomic insights into mechanisms of carbon coating on titania nanoparticle during flame synthesis
Atomic insights into mechanisms of carbon coating on titania nanoparticle during flame synthesis
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DOI：
10.1016/j.carbon.2022.09.002
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发表时间：
2022-09-18
期刊：
影响因子：
10.9
通讯作者：
Luo, Kai H.
中科院分区：
文献类型：
--
作者：
Hou, Dingyu;Mao, Qian;Luo, Kai H.
碳-金属氧化物（CMO）纳米复合材料由于其在储能材料和光催化剂方面的特殊性能而受到越来越多的研究。火焰气溶胶合成法为制备CMO纳米复合材料提供了一条很有前途的途径。各种CMO纳米复合材料已成功地通过火焰气溶胶技术在实验室中合成。然而，缺乏对这种材料的形成和生长机制的详细了解。因此，在这项研究中，反应力场分子动力学（ReaxFF MD）被部署，以获得原子的洞察到碳涂层的初始阶段的二氧化钛纳米粒子。在400 ~ 2500 K温度范围内，对18种典型碳氢化合物（C1 ~ C4和多环芳烃）在碳涂层中的燃烧行为进行了大量的数值模拟。结果表明，TiO 2纳米粒子不仅可以作为吸附核与周围的碳氢化合物发生物理吸附，而且可以与碳氢化合物形成C-Ti/O键，并从周围的碳氢化合物中夺取H原子。碳包覆的最佳温度范围为T = 1500 K，高温下碳氢化合物倾向于聚集形成较大的碳质物种，而不是包覆在颗粒表面，因为高温下促进了C-C键的形成。小分子化合物更倾向于化学包覆在纳米颗粒上，而PAH分子由于其稳定的电子结构和大尺寸而倾向于物理吸附在纳米颗粒表面。聚合物的包覆倾向与C-C三键数密切相关。
Carbon-metal oxide (CMO) nanocomposites have seen increasing research due to their extraordinary properties for energy storage materials and photocatalysts. Flame aerosol synthesis provides a promising route to producing CMO nanocomposites. Various CMO nanocomposites have been successfully synthesized through flame aerosol techniques in laboratories. However, a detailed understanding of the formation and growth mechanisms of such materials is lacking. Therefore, in this study, the reactive force-field molecular dynamics (ReaxFF MD) was deployed to gain atomic insights into the initial stage of carbon coating on the titania nanoparticle. We performed a large number of simulations of carbon coating with 18 typical hydrocarbon species in flames including aliphatics of C1-C4 species and polycyclic aromatic hydrocarbons (PAHs) at temperatures ranging from 400 K to 2500 K. We found that the titania nanoparticle can not only serve as a nucleus for physical adsorption of the surrounding hydrocarbons, but also can form C-Ti/O bonds with them, and abstract H atoms from the surrounding hydrocarbons. The optimal temperature range for carbon coating is T = 1500 K, hydrocarbons tend to gather to form larger carbonaceous species instead of coating onto the particle surface, as the formation of C-C bonds is promoted at high temperatures. Small aliphatics are favored to be chemically coated on the particle, while PAH molecules tend to be physically absorbed on the nanoparticle surface due to their stable electronic structure and large size. Coating tendencies of aliphatics are closely related to the number of C-C triple bonds.