Effect of Silver Dispersion on Photocatalytic Activity of Silver-Loaded Titanium Oxide

Abstract

The improvement of photocatalytic activity of TiO2 was studied by heat treating the mixtures of silver nitrate solution and three different sizes of TiO2 ; commercial-grade C02 (71 nm), P25 (24 nm) and homemade precipitated TiO2 (pTiO2, 11 nm). The activity toward nitrite degradation of large particles (C02) can be improved to be equal to small particles (P25) by optimum Ag loading. The optimum loading for pTiO2, P25 and C02 were 2.0, 0.75 and 0.75% which corresponded to the Ag contents of 1.35, 0.74 and 0.66%, respectively. Small particles tended to have high, while large particles tended to have low Ag contents as optimum levels. The agglomeration, dispersion and coverage of Ag on each TiO2 type were different and able to change the activity order. The Ag agglomerates on C02 were large and not well diffused while those on P25 were small and diffused homogeneously. As a result, the critical content (minimum Ag content creating measurable Ag agglomerates) of large TiO2 particles was relatively low (C02 = 0.66%) compared to that of the small ones (P25 = 1.24%).