It is known that fluoride and phosphate in aqueous solution can accelerate the photocatalytic degradation of phenol over anatase or P25 TiO2. But the mechanism still remains under debate. In this work, an anion-free anatase TiO2 is prepared, followed by deposition with 0.52 wt% Pt (Pt/TiO2). Reaction was performed in aqueous solution at initial pH 5.2, where 99% of anions were in the form of F- or H2PO4-. On the addition of 0.1-30 mM anions, the rate constants of phenol degradation (kobs) were all increased, confirming the positive effect of fluoride and phosphate, respectively. Interestingly, there was a linear relationship between the increase of kobs and the amounts of anion adsorption, the slope of which became larger in the order of fluoride > phosphate, and Pt/TiO2 > TiO2. These observations indicate that the positive effect of anions originates from the adsorbed anions on solid, and that fluoride was more active than phosphate. A (photo) electrochemical measurement showed that fluoride and phosphate were negative and positive, respectively, to O2 reduction, but they were all beneficial to phenol oxidation. Furthermore, in the presence of fluoride and phosphate, the flat band potentials of TiO2 were shifted by -159 and 89 mV, respectively. The former favors orbital overlapping of phenol with TiO2 valence band, and the latter favors orbital overlapping of O2 with TiO2 conduction band, all of which promotes the interfacial charge transfers. Since inorganic anions are widely present, this result would benefit the mechanism study of a semiconductor photocatalyis and its application.A general procedure for the synthesis of pure anatase is as following:at room temperature,50 mL tetrabutyl titanate was dissolved in 200 mL diethyl ether anhydrous; then, 60 mL acetic acid was added. After being stirred for 30 min, 75 mL of a mixture of deionized water and acetic acid in the ratio of 10:5 (v/v) was added dropwise to the precursor solution under vigorous stirring. The suspension was aged under airtight conditions at room temperature for 24 h. Then, the upper clear diethyl ether liquid was removed, and the remainder was dried at 100 oC for 24 h. After this, the sample was washed with deionized water to remove the residual acid and dried at the same temperature for 24 h as before. Finally, the sample was calcined at 400 oC for 2 h.