Visible light-induced photodegradation of rhodamine dyes over BiOCl, and the vital importance of the frontier orbital energy of the dye molecules in the reaction kinetics

Abstract The interfacial adsorption process and the white-light-induced photosensitized degradation of different rhodamine dyes (rhodamine B, rhodamine 6G, and rhodamine 101) on the wide-band-gap semiconductor BiOCl have been investigated. Adsorption of all the rhodamine molecules on BiOCl is an exothermic process and the saturated adsorption capacities were best deduced by Langmuir model fitting. By using quantum chemical calculations (Gaussian 03 software), the relationship between the frontier orbital energy of the dye molecules and the rate of photodegradation was also established. The calculated absolute value of E _LUMO was found to increase in the order Rh 101 < Rh 6G < RhB, which was similar to the trend of photodegradation reaction kinetics rate fitted by use of the pseudo-zero-order kinetics model.