Cobalt phosphate (CoPi) is a promising cocatalyst for the (photo)electrochemical oxidation of water over semiconductor electrodes in phosphate solution, but the effect of CoPi on organic oxidation reactions has been little studied. Herein, we report a compound-sensitive effect of CoPi on the TiO2-photocatalyzed oxidation phenol, 4-clflorophenol (CP), and 2,4-dichlorophenol (DCP) in a phospIlate,containing suspension at pH 7.0. A photochemical method was used to deposit Pt onto TiO2 and then CoPi onto both Pt/ TiO2 and TiO2. In all reactions, pt/TiO2 and,CoPi/TiO2 were.always more active and less active, respectively, than TiO2. comparison with Pt/TiO2, CoPi/Pt/TiO2 was less active for phenol oxidation but more active for CP and DCP oxidation. CoPi/ Pt/TiO2 was also more active than Pt/TiO2 for the photocatalytic reduction of O-2 into H2O2. For DCP oxidation in a phosphate free suspension at pH 7, however, CoPi/Pt/TiO2 was much less active than either Pt/TiO2 or TiO2, which is ascribed to the dissolution of Co2+ ions that act as recombination centers. It is proposed that the Co-IV species, formed by the hole oxidation of Co-II/III in CoPi, are surface-bound and short-lived.. They can react with a nearby adsorbed substrate (CP, DCP, and H2O2) but deactivate In the absence of either Pt (O-2 reduction catalyst) or phosphate (CoPi repairer). Moreover, there is a synergism between the CoPi-mediated hole transfer and the Pt-Mediated electron transfer, that improves the efficiency of the charge separation. and, consequently, increases the rates of O-2 reduction and organic oxidation.