Badaczewski Felix M, Loeh Marc O, Pfaff Torben, Wallacher Dirk, Clemens Daniel, Smarsly Bernd M
Institute of Physical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35492 Giessen, Germany.
Schunk Carbon Technology GmbH, Rodheimer Straße 59, 35452 Heuchelheim, Germany.
Beilstein J Nanotechnol. 2020 Feb 10;11:310-322. doi: 10.3762/bjnano.11.23. eCollection 2020.
This study is dedicated to link the nanoscale pore space of carbon materials, prepared by hard-templating of meso-macroporous SiO monoliths, to the corresponding nanoscale polyaromatic microstructure using two different carbon precursors wthat generally exhibit markedly different carbonization properties, i.e., a graphitizable pitch and a non-graphitizable resin. The micro- and mesoporosity of these monolithic carbon materials was studied by the sorption behavior of a relatively large organic molecule (-xylene) in comparison to typical gas adsorbates (Ar). In addition, to obtain a detailed view on the nanopore space small-angle neutron scattering (SANS) combined with in situ physisorption was applied, using deuterated -xylene (DPX) as a contrast-matching agent in the neutron scattering process. The impact of the carbon precursor on the structural order on an atomic scale in terms of size and disorder of the carbon microstructure, on the nanopore structure, and on the template process is analyzed by special evaluation approaches for SANS and wide-angle X-ray scattering (WAXS). The WAXS analysis shows that the pitch-based monolithic material exhibits a more ordered microstructure consisting of larger graphene stacks and similar graphene layer sizes compared to the monolithic resin. Another major finding is the discrepancy in the accessible micro/mesoporosity between Ar and deuterated -xylene that found for the two different carbon precursors, pitch and resin, which can be regarded as representative carbon precursors in general. These differences essentially indicate that physisorption using probe gases such as Ar or N can provide misleading parameters if to be used to appraise the accessibility of the nanoscale pore space.
本研究致力于将通过介观大孔SiO整体材料的硬模板法制备的碳材料的纳米级孔隙空间，与使用两种通常表现出明显不同碳化特性的不同碳前驱体（即可石墨化沥青和不可石墨化树脂）所对应的纳米级多芳族微观结构联系起来。通过与典型气体吸附质（Ar）相比，研究了相对较大的有机分子（对二甲苯）在这些整体碳材料中的吸附行为，以此来研究其微孔和介孔结构。此外，为了详细了解纳米孔空间，采用了小角中子散射（SANS）结合原位物理吸附，在中子散射过程中使用氘代对二甲苯（DPX）作为对比匹配剂。通过对SANS和广角X射线散射（WAXS）的特殊评估方法，分析了碳前驱体对碳微观结构在原子尺度上的结构有序性（包括尺寸和无序度）、纳米孔结构以及模板过程的影响。WAXS分析表明，与整体树脂相比，基于沥青的整体材料表现出更有序的微观结构，由更大的石墨烯堆叠和相似的石墨烯层尺寸组成。另一个主要发现是，对于两种不同的碳前驱体（沥青和树脂，它们通常可被视为代表性的碳前驱体），Ar和氘代对二甲苯在可及的微/介孔率方面存在差异。这些差异本质上表明，如果使用诸如Ar或N等探针气体的物理吸附来评估纳米级孔隙空间的可及性，可能会提供误导性参数。
