Influence of surface functionalities on ethanol adsorption characteristics in activated carbons for adsorption heat pumps
Influence of surface functionalities on ethanol adsorption characteristics in activated carbons for adsorption heat pumps
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DOI：
10.1016/j.applthermaleng.2014.06.018
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发表时间：
2014-11-22
影响因子：
6.4
通讯作者：
Miyawaki, Jin
中科院分区：
文献类型：
--
作者：
Kil, Hyun-Sig;Kim, Taegon;Miyawaki, Jin
为了开发高性能的吸附式热泵用活性炭，研究制冷剂分子在活性炭孔隙中的吸附行为具有重要意义。不仅孔结构，如孔径和形状，而且表面官能度强烈影响吸附行为，特别是对极性分子，如水和乙醇，这是典型的制冷剂的AHP。在这项研究中，我们研究了表面官能团对乙醇分子在碳微孔中的吸附行为的影响，使用模型AC具有不同量的含氧表面官能团，但可比的孔隙率。对于AC与增加量的表面官能团，乙醇吸附/脱附等温线显示出显着减少的吸附量和缩短的吸附平衡时间相比，在整个相对压力区域的表面官能团较少。这表明乙醇分子在具有丰富表面官能团的微孔中的扩散阻碍。为了验证我们的假设，我们研究了表面官能团的影响，乙醇分子的吸附行为，使用固态核磁共振技术。核磁共振结果表明，乙醇分子的羟基与表面官能团发生了强烈的相互作用，导致乙醇分子在具有含氧表面官能团的微孔中发生了定向吸附.电化学分析结果表明，含氧官能团的引入增加了微孔中电解质离子的扩散阻力，支持了我们的假设。(C)2014爱思唯尔有限公司版权所有。
To develop high-performance activated carbons (ACs) for adsorption heat pumps (AHPs), it is important to characterize the adsorption behaviors of the refrigerant molecules in the pores of ACs. Not only pore structures, such as pore size and shape, but also surface functionalities strongly influences the adsorption behaviors, especially for polar molecules, such as water and ethanol, which are typical refrigerants for AHP. In this study, we examined the influence of surface functional groups on the adsorption behaviors of ethanol molecules in carbon micropores using model ACs with different amounts of oxygen-containing surface functional groups but comparable porosities. For the AC with an increased amount of surface functional groups, ethanol adsorption/desorption isotherms showed significant decreases in the adsorption amounts and shortened adsorption equilibrium times compared to those with less surface functional groups throughout the entire relative pressure region. This suggests diffusional hindrance of ethanol molecules in micropores with abundant surface functional groups. To verify our hypothesis, we examined the influence of surface functional groups on the adsorption behavior of ethanol molecules using a solid-state NMR technique. The NMR results revealed that the hydroxyl group of ethanol molecules strongly interacts with the surface functional groups, giving rise to an oriented adsorption of ethanol molecules in the micropores with oxygen-containing surface functional groups. Furthermore, electrochemical analyses confirmed that diffusion resistance of electrolyte ions in the micropores increases after the introduction of oxygen-containing surface functional groups, which supports our hypothesis. (C) 2014 Elsevier Ltd. All rights reserved.