This study explores the photodegradation of 4-chlorophenol (4-CP). Coupled-photocatalyst systems are tested to determine whether the interparticle electron transfer (IPET) process improves the photodegradation efficiency. TiO2, ZnO and SnO2 are selected as photocatalysts. In the single-photocatalyst test, ZnO exhibits the highest catalytic activity. The pseudo first-order rate constant of the coupled-catalyst system, ZnO/SnO2, is approximately 22% higher than that of ZnO; these rate constants are 0.95 and 0.78 h(-1) at pH 11, respectively.