The photocatalytic water splitting kinetics has been analyzed in this paper. The experimental data are taken from the published works and fitted with different theoretical models. From the results, we find that the photocatalytic kinetics of water splitting can be described by Capelas-Mainardi–Vaz (CMV) model very well. This suggests that the water splitting kinetics can be regarded as a fractional first-order kinetics of the chemical reaction. Also, we notice that photocatalytic water splitting is not always completely a monotone kinetics process.