Heterogeneous photocatalysis is a promising advanced oxidation process for water purification. One of the limitations in photocatalysis has been inherently low photoefficiencies. Recent studies show that the photoefficiency of formate decomposition can be increased through the use of controlled periodic illumination. In this study, a Taylor vortex reactor was designed, constructed and tested as a novel photocatalytic reactor that incorporated illumination and dark recovery times via fluid mixing. A combination of the vortex motion and the limited light penetration depth into the photocatalytic slurry allowed the photocatalyst particles to move into and out of the illuminated portion of the reactor. The photoefficiency in the reactor increased by nearly a factor of three with the optimal conditions of an inner cylinder rotation rate of 300 rpm and an unusually high weight loading of 10 g/l of TiO2 photocatalyst.