The ZnCl2/450-AC, Fig. 1d, showed more porous structure than
the H3PO4/450-AC. Activation at higher temperatures, 600 or
750 C did not cause significant enhancement in porosity, and was
thus avoided for cost and energy saving purposes. A closer look at
the SEM image for the ZnCl2/450-AC shows that the solid has different types of pores with different parameters. Larger pores
with ~10 mm in diameter exist together with smaller pores in the
nanometer scale.