Model of micropore closure in hard carbon prepared from sucrose Original Research Article

A series of samples pyrolysed to different temperatures were synthesized from dewatered sucrose. These samples were characterised by wide-angle X-Ray scattering (WAXS), small-angle X-Ray scattering (SAXS), BET surface area and CO2 gas adsorption measurements. WAXS and SAXS measurements were used to determine the average number of graphene sheets stacked in a parallel fashion and the average micropore size (8–10 Å in radius), respectively. As the heat treatment temperature (HTT) was increased, WAXS and SAXS measurements show that the internal structure of these materials is changing in a fashion consistent with the falling card model. CO2 gas adsorption measurements show that the micropores in the sample are closing, forming an intermediate partially closed micropore, with increasing HTT (predominantly in the range 900–1400°C). A model of micropore closure is presented that describes the number of open micropores as a function of the heat treatment temperature and exposure time. A simple adsorption model based on the Langmuir equation is presented and was used to determine the number of open micropores in the sample.