The specific surface areas of P25 and GT with different addition ratios were determined by the BET method using adsorption data, whereas the pore volume and pore size distribution were derived using the BJH model based on desorption isotherms. Fig. 2 (inset) shows the adsorption–desorption isotherms and
the corresponding pore size distribution curves of the catalysts.
All catalysts exhibited similar type IV isotherms (Sing et al., 1985) with an H3 hysteresis loop at a relative pressure close to
unity, which are typical characteristics of mesoporous mate-rials (Liuet al., 2011b). The pore sizedistributions (inset inFig. 2) of the GT samples were broad (from 2 to over 100 nm),
indicating the presence of mesopores and macropores (Xiang
et al., 2011b).