A model based on spherical TiO2 nanoparticles was developed to study heterogeneous photocatalysis based on TiO2 in the case of indirect interfacial charge transfer. In this model, the effect of light intensity (I-0), grain size (r(0)), carrier lifetime (tau(p)), and minority carrier diffusion coefficient (D-p) on the quantum yield (QY) of photocatalytic reactions was investigated in detail. Under conditions of sufficiently low incident-light intensity, the QY was found to be alpha I-0, while it decreased rapidly with an increase in I-0. In addition, the QY went to zero at a critically high light intensity. Furthermore, the QY was found to decrease with increasing r(0) due to the bulk-recombination loss, and the effect of r(0) on the QY became increasingly stronger with the increase in I-0. The QY decreased with the decrease in tau(p) and D-p, which was more apparent at the critically high I-0. Under conditions of low [(RH2)(aq)], the QY increased with an increase in [(RH2)(aq)], while it remained nearly constant at high [(RH2)(aq)] clue to the fact that the photoinduced electron interfacial transfer became the limiting step for photocatalytic reactions in the case of high [(RH2)(aq)]. (C) 2010 Elsevier Ltd. All rights reserved.