Photocatalytic oxidations (PCOs) of heptane, trichloroethylene (TCE), ethanol, acetaldehyde, and toluene were carried out on sulfated TiO 2 (SO 4 2 - /TiO 2 ) and Degussa P-25. Coverages of all organics on SO 4 2 - /TiO 2 were significantly higher than on P-25, but P-25 was more active for PCO at room temperature. Pulse PCO at room temperature suggests that steady-state PCO rates of acetaldehyde on the two catalysts may be similar, however. During PCO of heptane at room temperature, SO 4 2 - /TiO 2 deactivated slower than P-25 so that the CO 2 formation rate on P-25 was only 11% greater than that on SO 4 2 - /TiO 2 after five 110μmol/gcatalyst pulses of heptane.Both pulse and steady-state PCO of TCE showed that although P-25 was more active than SO 4 2 - /TiO 2 , the CO 2 production rate decreased with time on P-25 but not on SO 4 2 - /TiO 2 . Furthermore, CO 2 selectivity increased with time as PCO of TCE approached steady-state on SO 4 2 - /TiO 2 , whereas it decreased on P-25. Selectivity to phosgene formation on P-25 was twice that on SO 4 2 - /TiO 2 .Sulfated TiO 2 was more active and deactivated more slowly than P-25 during PCO of acetaldehyde above 373K. Since acetaldehyde is an intermediate for PCO of several organics, SO 4 2 - /TiO 2 may be preferable to Degussa P-25 for PCO at elevated temperatures.