Microporosity and nanostructure of activated carbons: characterization by X-ray diffraction and scattering, Raman spectroscopy and transmission electron microscopy

Microporosity and structure of a set of activated carbons was studied by combination of N-2 and CO2 adsorption, Transmission Electron Microscopy (TEM), X-ray diffraction and scattering and multiwavelength Raman spectroscopy. It is shown that correlations between measured parameteres may be established for a given set of activated carbons, most often obtained from a same precursor. Comparison of results of TEM images processing and of Small-angle scattering with adsorption data suggests that super-micropores (0.7-2 nm) are highly variable in shape and strongly deviate from the ideal slit pore model. These pores are likely located in between disordered continuous graphene stacks. It is shown that Small-angle scattering is mostly caused by supermicropores; contribution of other types of porosity is of secondary importance. For a set of carbons with similar structure, a reasonable correlation between Guinier radii and pore width obtained from N-2 adsorption can be found; however, the reason for the observed offset between the data sets remain uncertain. Sensitivity of the Raman scattering to atomic scale processes leads to poor or unclear correlations between the spectroscopic and structural data, although some notable exceptions are noted.