Photocatalytic oxidative C-C bond cleavage of 1,2-ethanediol initiated by aqueous titanium dioxide dispersion - Influence of Ag+ on the catalytic activity

TiO2-mediated photooxidation of 1,2-ethanediol in the presence of oxygen by light of lambda(ex) > 300 nm results in its C-C bond cleavage to yield HCH O. The kinetics of reaction, monitored by following the product, obeys Lang muir-Hinshelwood's equation. The reaction rate constant and the adsorption equilibrium constant for this process are evaluated to be 1.9 x 10(-6) mol dm(-3) s(-1) and 16 dm(3) mol(-1), respectively. The presence of O-2 and Ag + enhance the reaction rate and the yield of HCHO by trapping the conductio n band electron. The oxidation is suggested to take place by direct hole as well as by trapped hole transfer. At pH 12 the reaction efficiency has bee n observed to be about 14 times hipher to that of at pH 2.5. About 3.4 wt% Ag+ exhibits the maximum cocatalytic effect. The participation of Ag2+ in t he catalytic action is ruled out. A scheme of photocatalytic oxidation is d iscussed.