J. Z. Bloh
J. Phys. Chem. C., 121 (2017), 844–851 doi:10.1021/acs.jpcc.6b09808.
Doping with metal ions is a simple and convenient method of improving the photocatalytic activity of semiconducting materials. As revealed previously (Bloh et al. J. Phys. Chem. C 2012, 116, 25558−25562), the optimal doping ratio is strongly dependent on the particle size and can be predicted with an empirical function. This work expands on that model, providing a more accurate physical explanation of the observed behavior. The new model is based on the theory that only the fraction of dopants that is situated on the particle surface has a beneficial effect. Analysis of almost 200 data points from the literature revealed that the optimal doping ratio corresponds well to an equivalent of 3.54 surface dopant atoms per particle, apparently independent of other parameters such as material or dopant. With this knowledge, the optimal doping ratio for a given catalyst can be predicted with good precision. The findings also suggest that doping and grafting essentially cause the same effect, the latter while avoiding detrimental bulk dopants. Hence, bulk doping should be avoided in favor of surface doping or grafting.