Photoactive mechanism of TiO ₂ catalytic system in scavenging of hydroxyl radical with alcohols as scavengers

In photocatalytic oxidation, the photocatalytic properties of photocatalysts are commonly attributed to hydroxyl radicals (·OH), superoxide radicals (·O 2 − ), and hole radicals (h + ). In general, evaluating radical activity is crucial for studying the photocatalytic mechanism. Previous studies have reported that alcohols are commonly used to characterise the magnitude of hydroxyl radical activity. However, this work found that alcohols as OH scavengers exhibited an inhibiting effect on titanium dioxide (TiO 2 ) photocatalytic systems at lower concentrations, whilst an opposite effect at higher concentrations, which was diverged significantly from the findings reported. This study provided a detailed investigation of the effect of alcohols concentration on the photocatalytic process. The results show that the catalytic process could be facilitated by introducing high concentrations of alcohols to increase the existence time of O 2 − and h + . Finally, further studies confirmed that oxidative dehydrogenation is an important pathway for alcohols to act as OH scavengers. The photoactive mechanism was proposed based on the influence of alcohols concentration on the photocatalytic process.