A quantitative analysis of carbon edge sites and an estimation of graphene sheet size in high-temperature treated, non-porous carbons

By using non-graphitizable and graphitizable carbons prepared from poly(furfulyl alcohol) and poly(vinyl chloride), respectively, an attempt is made to determine the number of carbon edge sites by analyzing their hydrogen content and the amounts of surface oxygen complexes and localized spins. It is found that, at the present preparation conditions, the number of hydrogen-terminated edges is much higher than the number of surface oxygen complexes regardless of the type of carbon and the heat-treatment temperature, but the contribution of the localized spins derived from σ free radicals in closed spaces and/or triplet carbene/carbyne species may become comparable to the hydrogen content when the heat-treatment temperature is higher. Moreover, the average sizes of graphene layers in these carbons are estimated from the total number of edge sites. This analysis suggests that the actual size in the poly(furfulyl alcohol)-derived carbons is much larger than the size detected with transmission electron microscopy. This large difference is discussed in relation to a real structure of graphene layers in non-graphitizable carbons.