The SEM images of the AC samples derived from eucalyptus
wood with ZnCl2, and H3PO4 are shown in Fig. 3. As shown in these
figures, pores of different size and different morphology within the
structure of the AC samples, with mesopores and micropores
hiding inside the ACs. It should be noted that the external surface of
the AC samples prepared by H3PO4have larger pore size compared
to the other AC samples. The reason could be the evaporation of
H3PO4 during carbonization leaving empty space previously
occupied by H3PO4.