Photocatalytic degradation as Davidson–Cole relaxation in time domain

Photocatalytic degradation processes of different materials are fitted with Mittag-Leffler function and incomplete gamma function,which are response functions for Cole–Cole relaxation and Davidson–Cole relaxation.The fitting results show that both functions can fit experimental data fairly well.The order of derivative in the kinetic differential equations can be either less,or greater than one.In the case of the order of derivative is greater than one,only incomplete gamma function is reasonable for describing the photocatalytic degradation.This work further confirms the existence of the universality in photocatalytic degradation kinetics.