Effects of supercritical-CO2 treatment on the pore structure and H2 adsorptivity of single-walled carbon nanohorns

IF 5.5 3区材料科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Carbon Letters Pub Date : 2024-06-15 DOI:10.1007/s42823-024-00757-7

Nam Ryeol Kim, Jae-Hyung Wee, Chang Hyo Kim, Dong Young Kim, Katsumi Kaneko, Cheol-Min Yang

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Abstract

We investigated the effects of supercritical-CO₂ treatment on the pore structure and consequent H₂ adsorption behavior of single-walled carbon nanohorns (SWCNHs) and SWCNH aggregates. High-resolution transmission electron microscopy and adsorption characterization techniques were employed to elucidate the alterations in the SWCNH morphology and aggregate pore characteristics induced by supercritical-CO₂ treatment. Our results confirm that supercritical-CO₂ treatment reduces the interstitial pore surface area and volume of SWCNH aggregates, notably affecting the adsorption of N₂ (77 K), CO₂ (273 K), and H₂ (77 K) gasses. The interstitial porosity strongly depends on the supercritical-CO₂ pressure. Supercritical-CO₂ treatment softens the individual SWCNHs and opens the core of SWCNH aggregates, producing a partially orientated structure with interstitial ultramicropores. These nanopores are formed by the diffusion and intercalation of CO₂ molecules during treatment. An increase in the amount of H₂ adsorbed per interstitial micropore of the supercritically modified SWCNHs was observed. Moreover, the increase in the number and volume of ultramicropores enable the selective adsorption of H₂ and CO₂ molecules. This study reveals that supercritical-CO₂ treatment can modulate the pore structure of SWCNH aggregates and provides an effective strategy for tailoring the H₂ adsorption properties of nanomaterials.

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超临界二氧化碳处理对单壁纳米碳角孔隙结构和 H2 吸附性的影响

我们研究了超临界二氧化碳处理对单壁碳纳米管（SWCNHs）和单壁碳纳米管聚合体的孔隙结构及H2吸附行为的影响。我们采用了高分辨率透射电子显微镜和吸附表征技术来阐明超临界二氧化碳处理对 SWCNH 形态和聚集体孔隙特征的改变。我们的结果证实，超临界-CO2 处理降低了 SWCNH 聚合物的间隙孔表面积和体积，明显影响了对 N2（77 K）、CO2（273 K）和 H2（77 K）气体的吸附。间隙孔隙率在很大程度上取决于超临界二氧化碳压力。超临界二氧化碳处理会软化单个超临界碳化萘，并打开超临界碳化萘聚集体的核心，产生具有间隙超微孔的部分定向结构。这些纳米孔是在处理过程中通过二氧化碳分子的扩散和插层形成的。据观察，超临界改性 SWCNHs 的每个间隙微孔吸附的 H2 量有所增加。此外，超微孔数量和体积的增加使 H2 和 CO2 分子的吸附具有选择性。这项研究揭示了超临界二氧化碳处理可以调节 SWCNH 聚合物的孔隙结构，为定制纳米材料的 H2 吸附特性提供了一种有效的策略。

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来源期刊

Carbon Letters CHEMISTRY, MULTIDISCIPLINARY-MATERIALS SCIENCE, MULTIDISCIPLINARY

CiteScore

7.30

自引率

20.00%

发文量

118

期刊介绍： Carbon Letters aims to be a comprehensive journal with complete coverage of carbon materials and carbon-rich molecules. These materials range from, but are not limited to, diamond and graphite through chars, semicokes, mesophase substances, carbon fibers, carbon nanotubes, graphenes, carbon blacks, activated carbons, pyrolytic carbons, glass-like carbons, etc. Papers on the secondary production of new carbon and composite materials from the above mentioned various carbons are within the scope of the journal. Papers on organic substances, including coals, will be considered only if the research has close relation to the resulting carbon materials. Carbon Letters also seeks to keep abreast of new developments in their specialist fields and to unite in finding alternative energy solutions to current issues such as the greenhouse effect and the depletion of the ozone layer. The renewable energy basics, energy storage and conversion, solar energy, wind energy, water energy, nuclear energy, biomass energy, hydrogen production technology, and other clean energy technologies are also within the scope of the journal. Carbon Letters invites original reports of fundamental research in all branches of the theory and practice of carbon science and technology.