Semiconductor photocatalysis has long been considered as a promising approach for water pollution remediation. However, limited by the recombination of electrons and holes, low kinetics of photocatalysts and slow reaction rate impede large-scale applications. Herein, we addressed this limitation by developing a triphase photocatalytic system in which a photocatalytic reaction is carried out at air-liquid-solid joint interfaces. Such a triphase system allows the rapid delivery of oxygen, a natural electron scavenger, from air to the reaction interface. This enables the efficient removal of photogenerated electrons from the photocatalyst surface and minimization of electron-hole recombination even at high light intensities, thereby resulting in an approximate 10-fold enhancement in the photocatalytic reaction rate as compared to a conventional liquid/solid diphase system. The triphase system appears an enabling platform for understanding and maximizing photocatalyst kinetics, aiding in the application of semiconductor photocatalysis.