Nano TiO₂ photocatalytic decomposition of flow gas-phase methanol was investigated under 253.7 nm UV light. The result indicated that oxygen content exerted a significant influence on methanol photocatalytic decomposition. In the absence of oxygen, there was no distinct decomposition even with abundant water vapor. It was concluded that after hole-electron pairs were induced by ultraviolet light, the hole then oxidized methanol directly, forming methanol free radical cation, which would be further oxidized in the presence of oxygen. Methanol oxidation process was a multi-path reaction, and in macro view a pseudo-first-order reaction with decomposition rate constant of 9.78×10^－3 s^－1 in the presence of air and 1.79×10^－2 s^－1 in the presence of oxygen.

Key words: photocatalysis, methanol, hole, direct oxidization, free radical