Photocatalytic decomposition of formic acid and methyl formate on TiO2 doped with N and promoted with Au. Production of H2

The photo-induced vapor-phase decompositions of formic acid and methyl formate were investigated on pure, N-doped and Au-promoted TiO2. Infrared (IR) spectroscopic studies revealed that illumination initiated the decomposition of adsorbed formate formed in the dissociation of formic acid and located mainly on TiO2. The photocatalytic decompositions of formic acid and methyl formate vapor on pure TiO2 occurred to only a limited extent. The deposition of Au on pure or doped TiO2 markedly enhanced the extent of photocatalytic decomposition of formic acid. The main process was dehydrogenation to give H2 and CO2. The formation of CO occurred to only a very small extent. Addition of O2 or H2O to the formic acid decreased the CO level from ∼0.8% to ∼0.088%. Similar features were experienced in the photocatalytic decomposition of methyl formate, which dissociated in part to give surface formate. Experiments over Au deposited on N-doped TiO2 revealed that the photo-induced decomposition of both compounds occurs even in visible light.