The photocatalytic decomposition (PCD) of aliphatic alcohols, acids, and esters in an inert atmosphere on TiO2 and Pt/TiO2 at room temperature was studied using transient reaction techniques. The addition of Pt to TiO2 increased the rate of reaction and changed the selectivity significantly, even though Pt is not a photocatalyst and does not have a measurable rate of thermal catalytic activity at room temperature. Although none of the reactants decomposed to form H-2 on TiO2, significant amounts of H-2 formed for some reactants during on Pt/TiO2, presumably because H atoms spill over onto Pt and recombine to form H-2. Hydrogen formed on Pt/TiO2 for all the organics with H bonded to the carbon in a -C-O- group. When only alkyl groups were bonded to the carbon in a -C-O- group, alkanes formed but not H-2. Abstraction of a H atom appears to be the first step in PCD of alcohols, acids, and esters. Alcohols react to form the corresponding aldehyde and either H-2 or alkanes. Acids and esters react similarly through two parallel pathways, and one pathway extracted lattice oxygen. (C) 2001 Academic Press.