The Nitric Oxide Dimer Reaction in Carbon Nanopores.
The Nitric Oxide Dimer Reaction in Carbon Nanopores.
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DOI：
10.1021/acs.jpcb.7b10876
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
Deepti Srivastava;C. Turner;E. Santiso;K. Gubbins
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文献类型：
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作者：
Deepti Srivastava;C. Turner;E. Santiso;K. Gubbins
当被限制在孔宽约为 1 nm 的纳米多孔碳（活性碳纤维或碳纳米管）内时，发现一氧化氮完全反应形成二聚体 (NO)2，即使在与孔相平衡的本体气相中几乎不存在二聚体。此外，在实验研究的范围内改变温度时，二聚体的产率没有变化。早期的分子模拟研究表明，碳纳米孔中二聚体的形成显着增加，但二聚体的产率远低于实验结果，并且随着温度的升高而迅速下降。在这里，我们报告了在狭缝状孔和单壁碳纳米管中该反应的从头算和分子模拟研究。从头计算表明，一氧化氮二聚体与碳形成弱化学键，键能比之前研究中假设的范德华能强20倍以上。考虑到这一点，预测的二聚体产量与实验值非常一致，其温度依赖性也是如此。我们还报告了这种受限反应混合物的压力张量分量的结果。孔壁附近的局部切向压力高达数百万巴，反映了强大的纳米级力。
When confined within nanoporous carbons (activated carbon fibers or carbon nanotubes) having pore widths of about 1 nm, nitric oxide is found to react completely to form the dimer, (NO)2, even though almost no dimers are present in the bulk gas phase in equilibrium with the pore phase. Moreover, the yield of dimer is unchanged upon varying the temperature over the range studied in the experiments. Earlier molecular simulation studies showed a significant increase in dimer formation in carbon nanopores, but the dimer yield was considerably less than that found in the experiments, and decreased rapidly as the temperature was raised. Here, we report an ab initio and molecular simulation study of this reaction in both slit-shaped pores and single-walled carbon nanotubes. The ab initio calculations show that the nitric oxide dimer forms a weak chemical bond with the carbon, and the bonding energy is more than 20 times stronger than the van der Waals energy assumed in the previous studies. When this is accounted for, the predicted dimer yield is in good agreement with the experimental values, as is its temperature dependence. We also report results for the pressure tensor components for this confined reactive mixture. Local tangential pressures near the pore walls are as high as millions of bar, reflecting the strong nanoscale forces.