Water adsorption on nitrogen-doped carbons for adsorption heat pump/desiccant cooling: Experimental and density functional theory calculation studies
Water adsorption on nitrogen-doped carbons for adsorption heat pump/desiccant cooling: Experimental and density functional theory calculation studies
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DOI：
10.1016/j.apsusc.2019.06.267
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发表时间：
2019-10-30
影响因子：
6.7
通讯作者：
Yogo, Katsunori
中科院分区：
文献类型：
--
作者：
Fujiki, Junpei;Yogo, Katsunori
通过使用碱金属碳酸盐（Na2CO3、K2CO3、Rb2CO3 和 Cs2CO3）化学活化壳聚糖制备氮掺杂多孔碳，并测量制备的碳的水吸附等温线，以评估碳在吸附热泵/干燥剂冷却中的性能。将碱金属碳酸盐活化剂预掺杂到壳聚糖前体中导致高度发达的微孔结构并引入大孔。大孔结构显然取决于碱金属碳酸盐活化剂。 Na2CO3 由于硬模板效应而产生二维大孔，而其他碱金属碳酸盐活化剂则产生具有不同孔径的三维大孔。基于氮掺杂活性炭的 X 射线光电子能谱分析的密度泛函理论计算研究表明，吡啶类（吡啶、吡啶酮和吡啶 N-氧化物）、酰胺和季氮基团可能对低压水吸附有效。虽然制备的碳在 P/P-0 > 0.5 时的水吸附能力随着微孔体积的增加而增加，但在低压区域 (P/P-0 < 0.1) 的水吸附能力取决于氮或氧官能团的表面密度。此外，对于具有适当表面密度的氮官能团的碳，观察到了适合吸附热泵/干燥剂冷却的水等温线的形状。
Nitrogen-doped porous carbons were prepared via chemical activation of chitosan using alkali-metal carbonates (Na2CO3, K2CO3, Rb2CO3, and Cs2CO3), and the water adsorption isotherms of prepared carbons were measured to estimate the performance of the carbons in adsorption heat pump/desiccant cooling. Pre-doping of an alkali carbonate activator into the chitosan precursor resulted in a highly developed micropore structure and the introduction of macropores. The macropore structure clearly depended on the alkali carbonate activator. Na2CO3 resulted in two-dimensional macropores because of the hard-template effect, whereas the other alkali carbonate activators resulted in three-dimensional macropores with different cell sizes. A density functional theory calculation study based on X-ray photoelectron spectroscopy analyses of nitrogen-doped activated carbons indicated that pyridinic (pyridine, pyridone, and pyridine N-oxide), amide, and quaternary N groups might be effective for low-pressure water adsorption. Although the water adsorption capacities of the prepared carbons at P/P-0 > 0.5 increased with increasing micropore volume, those at the low-pressure region (P/P-0 < 0.1) were dependent on the surface density of nitrogen or oxygen functional groups. In addition, the shape of water isotherms preferable for adsorption heat pump/desiccant cooling was observed for the carbons with an appropriate surface density of nitrogen functional groups.