Vertically Oriented Propylene Carbonate Molecules and Tetraethyl Ammonium Ions in Carbon Slit Pores

We report the vertical alignment of propylene carbonate (PC) molecules interacting with Et4N+ and BF4- which are confined in extremely narrow slit pores (w similar to 0.7 nm) of carbide-derived carbon and pitch-based activated carbon fiber. On the basis of X-ray diffraction (XRD), electron radial distribution function analysis reveals that the nearest PC-PC distance is 0.05-0.06 nm shorter than that in the bulk solution, indicating dense packing of PC molecules in the pores. This confinement effect results from the vertically aligned PC molecules, which are indicated by the reverse Monte Carlo analysis. The ensemble structure of PC molecules in the subnanometer carbon pores will provide better understanding the supercapacitor function.