Methanol Photooxidation in a Black Body Like Reactor Using Bismuth-Based Heterojunctions

The photocatalytic activity of different bismuth-based heterojunctions by the reaction rates (dn/dt) and quantum yields (phi lambda) in aqueous suspension employing a black body like reactor (BBR), is reported. Four photocatalysts and their heterojunctions were tested while keeping the beta-Bi2O3 in common: Cu2O/beta-Bi2O3, ZnO/beta-Bi2O3, and Na0.5Bi0.5TiO3/beta-Bi2O3. The high optical density of the photocatalyst and the negative geometry of the reactor allowed measuring the quantum yields with good reproducibility since the catalyst is the only light absorbing species. The number of photons absorbed by the photocatalysts per unit time (photon flux) was determined by chemical actinometry for UV and visible light. The photocatalytic activity was measured for the oxidation of methanol as a model compound. Formaldehyde was measured as the photooxidation product employing Nash method. The charge transfer process mechanism in the photocatalytic reaction is shown based on the band gap energies, band edge potentials, and band alignment in the case of heterojunctions.