Fig. 4b shows the evolution of the total pore volume and micropore volume of the carbons obtained for different activation times. The data presented correspond to the activation reactions carried out at 850 8C, and both the trend and the values obtained are similar to those obtained at 900 8C. As observed, the micropore volume represents a small fraction of the total pore volume,around 10% of the total pore volume. Both the total pore volume and micropore volume reach the maximum for burn-off values in the 50–60% range and longer activation times give way to lower values of these parameters. This trend is explained by the growth and destruction of micropores walls to produce meso- and macropores [14].