Recent experiments have demonstrated impressive photocatalytic performances in spin-polarized materials. The existence of spin-dependent recombination between spin split bands has been suggested as the cause for at least part of the improved photocatalysis. To test the efficacy of this mechanism, we develop a set of rate equations for carrier charge and spin to shed light on recent experiments with metal-defected or doped oxides, magnetically decorated metal-organic frameworks, and magnetically doped perovskites. Our results show that recombination will be dependent on the band spin polarization and the lengthening of decay times can be optimized by engineering the electronic structure.