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This work has been undertaken to study the influences of pH value on the characteristics and activity of photocatalyst by deposition-precipitation method during its preparation process.A series of Pt-modified TiO2 were prepared by deposition-precipitation method at different pH values as well as wet impregnation method,and characterized by XRD,XPS,TEM,UV-Vis and photoluminescence(PL).It was found that the catalysts had the highest photocatalytic activity for NO conversion when pH value was kept at around 7.And the sample prepared by deposition-precipitation method showed higher activity than that by impregnation method.This was mainly due to their high value in highly-dispersed platinum oxides(PtOx)content on the surface of the catalysts.The results from UV-Vis absorption showed that highest absorbance was obtained for Pt/TiO2 prepared at pH values of around 7.And PL spectra results indicated that the recombination rate of photogenerated electrons and holes of the samples prepared by deposition-precipitation method was lower than that prepared by impregnation method.And in the zeta potential study,the pH values for the isoelectric point of the preparing slurry of 0.05 wt.％Pt/TiO2 and 0.5 wt.％Pt/TiO2 were determined to be 6.5-8.5,which further confirmed the enrichment of PtOx dopants for the catalysts repapered when pH value was around 7.