H2SO4 adsorption was studied by solid-state 2H-NMRand temperature-programmed desorption (TPD) on a series of pitch-based activated carbon fibers (ACFs), and compared to their electric double-layer capacitance in H2SO4 and Et 4NBF4. Three states of H2SO4 were found by magic angle spinning (MAS)2H-NMR, namely species adsorbed on the walls, trapped in the pores, and staying over the outer surface of the ACFs, respectively. Protons of H2SO4 are strongly fixed on the walls of small pores whereas in the larger pores they are rather mobile due to exchange. The adsorbed protons on the pore walls contribute to the capacitance while their exchange with the protons of H2SO4 in the pores appears to decrease their contribution to the capacitance. The capacitance of ACFs with smaller surface area is correlated to the amount of SO2 desorbed by TPD up to 200 °C. By contrast, for other ACFs of larger surface area the amount up to the same temperature was found to be much larger than their capacitance. The contribution of H2SO4 adsorbed in the latter ACFs is much less effective for their capacitance.
|Number of pages||6|
|Journal||Applied Physics A: Materials Science and Processing|
|Issue number||4 SPEC. ISS.|
|Publication status||Published - Mar 1 2006|
All Science Journal Classification (ASJC) codes
- Materials Science(all)