Tetrahydrofuran-induced K and Li doping onto poly(furfuryl alcohol)-derived activated carbon (PFAC): influence on microstructure and H2 sorption properties

We have doped poly(furfuryl alcohol)-derived activated carbon (PFAC) with two alkali metals, potassium (K) and lithium (Li), by previously reacting the metals with naphthalene in the presence of tetrahydrofuran (THF), followed by introducing them to pristine PFAC. The THF molecule causes a minor alteration of the microstructure of PFAC as confirmed by Raman spectra, X-ray diffraction, and pore textural analysis. Raman spectra and X-ray diffraction indicated a slight localized ordering toward the stacking defects of disordered carbon, as in PFAC, which can be attributed to the movement of THF molecules within the internal planes of graphene sheets. Pore textural analysis confirmed the lowering of the specific surface area and pore volume of both K- and Li-doped PFACs (BET SSA, 1378 m(2)/g (PFAC); 1252 m(2)/g (K-PFAC), 1081 m(2)/g (Li-PFAC)). Volumetric hydrogen adsorption measurements at temperatures of 298, 288, 273, and 77 K and pressures of up to 1 bar indicated the enhanced adsorption potential imposed by the presence of alkali metals, which can be reconfirmed by the elevated heats of adsorption of metal-doped PFACs (Li-PFAC, -(10-11) kJ/mol; K-PFAC, -(16-19) kJ/mol) compared to that of pristine PFAC (-9.6 kJ/mol).