Zheng L, Li W B, Chen J L
Department of Chemistry, Tsinghua University Haidian District Beijing 100084 China
Graduate School at Shenzhen, Tsinghua University, University Town Nanshan District Shenzhen 518055 China.
RSC Adv. 2018 Aug 24;8(52):29767-29774. doi: 10.1039/c8ra04367a. eCollection 2018 Aug 20.
Nitrogen doped hierarchical activated carbons with high surface areas and different pore structures are prepared form polyacrylonitrile fibers through KOH activation by two steps. It is found that the specific surface area and porosity of the activated carbons depend strongly on the activation temperatures. The specific surface area increases from 607 m g to 3797 m g when the activation temperature increases from 600 °C to 800 °C, and then decreases to 3379 m g at 900 °C. It shows that the hierarchical activated carbon prepared at a moderate activation temperature of 700 °C exhibits the largest CO capture amount, , 5.25 and 3.63 mmol g at 273 and 298 K, respectively, under the pressure of 1 bar. The excellent CO capture properties are due to the high specific surface area of 2146 m g and high nitrogen content (5.2 wt%) of the obtained sample. On the other hand, when used as supercapacitor electrodes, the sample with the activation temperature at 800 °C shows the largest specific capacitance of 302 F g at a current density of 1 A g in 6 M KOH aqueous electrolyte, with an excellent rate capability of 231 F g at 10 A g. Furthermore, a nearly linear relationship between nitrogen content in the nitrogen doped activated carbons and specific CO uptake as well as the specific capacitance were first established, indicating nitrogen doping was playing key roles in improving CO adsorption and supercapacitor performance. The experimental results indicate that the thus obtained nitrogen doped hierarchical activated carbons are very promising for reducing CO green house gas by adsorption as well as storing energy as utilized in supercapacitors.
通过两步KOH活化法，以聚丙烯腈纤维为原料制备了具有高比表面积和不同孔结构的氮掺杂分级活性炭。研究发现，活性炭的比表面积和孔隙率强烈依赖于活化温度。当活化温度从600℃升高到800℃时，比表面积从607 m²/g增加到3797 m²/g，然后在900℃时降至3379 m²/g。结果表明，在700℃的适中活化温度下制备的分级活性炭在1 bar压力下，于273 K和298 K时分别表现出最大的CO捕获量，即5.25和3.63 mmol/g。优异的CO捕获性能归因于所得样品2146 m²/g的高比表面积和5.2 wt%的高氮含量。另一方面，当用作超级电容器电极时，在6 M KOH水溶液电解质中，活化温度为800℃的样品在电流密度为1 A/g时表现出302 F/g的最大比电容，在10 A/g时具有231 F/g的优异倍率性能。此外，首次建立了氮掺杂活性炭中氮含量与特定CO吸收量以及比电容之间几乎呈线性的关系，表明氮掺杂在改善CO吸附和超级电容器性能方面起着关键作用。实验结果表明，如此获得的氮掺杂分级活性炭在通过吸附减少CO温室气体以及用作超级电容器储能方面非常有前景。
