The City College of New York and The Graduate School of CUNY, New York, New York 10031, United States.
Langmuir. 2013 Jun 11;29(23):6895-902. doi: 10.1021/la4008137. Epub 2013 May 31.
Silica-carbon composite samples containing various carbon contents deposited within a silica gel matrix were synthesized. The composites were evaluated as nitrogen dioxide adsorbents at ambient conditions in either wet (70% RH) or dry air streams. The surface chemistry and textural features of the initial and exposed samples were characterized using nitrogen adsorption, potentiometric titration, thermal analysis, and FT-IR. The deposition of the carbon phase significantly increased the amount of NO2 adsorbed in comparison with that adsorbed on the silica gel. With an increase in the amount of carbon an increase in the performance was found. The positive effect was especially noticed when water was present in the system. An oxidation of the surface and release of NO was observed. The acidification/oxidation of the surface is more pronounced in moist conditions, and it is linked to the formation of nitric acid adsorbed in the pore system. The carbon phase besides providing some level of hydrophobicity also brings phenolic groups to the system, on which immobilization of NO2 takes place via nitrification reactions.
合成了一种含有不同碳含量的硅-碳复合材料，沉积在硅胶基质中。在湿（70%RH）或干燥空气流中，将复合材料在环境条件下作为二氧化氮吸附剂进行评估。采用氮吸附、电位滴定、热分析和 FT-IR 对初始和暴露样品的表面化学和结构特征进行了表征。与在硅胶上吸附的二氧化氮相比，碳相的沉积显著增加了吸附的二氧化氮量。随着碳量的增加，性能得到了提高。当系统中存在水时，会特别注意到这种积极的影响。观察到表面氧化和一氧化氮的释放。在潮湿条件下，表面的酸化/氧化更为明显，这与吸附在孔系统中的硝酸的形成有关。碳相除了提供一定程度的疏水性外，还会将酚类基团引入到体系中，通过硝化反应，NO2 被固定在这些基团上。
