Scope for spherical Bi2WO6 quazi-perovskites in the artificial photosynthesis reaction – the effects of surface modification with amine groups

The synthesis, characterisation, modification (with n-propyl amine groups) of Bi2WO6 particles and the scope for its application in artificial photosynthesis reactions is described. The synthesis involves microwave activation of spherical Bi2O3 precursors followed by a hydrothermal treatment in the presence of Na2WO4. These are characterised using electron microscopy (TEM and SEM), BET, XRD, FTIR, FT-Raman and UV-Visible spectroscopies and CO2 TPD. Subsequently this material is modified through the condensation of propyl amine groups to surface hydroxyl groups, and the composites prepared are characterised using FTIR and D-FTIR following exposure to CO2. Both the spherical particles and the amine-modified analogues are applied in the artificial photosynthesis reaction under batch conditions. O2, CO and CH4 are the observed gaseous products during the reaction and there is FTIR evidence for the formation of adsorbed alcohols and carbonylated products. Although the modification with amine groups decreased the overall photocatalytic reactivity, it also altered the product selectivity with respect to the CH4/CO ratio. The catalyst tends to improve the oxygen production ability after about 20h of operation, with a decline in CH4 and CO production, indicating that other condensates are probably generated. This opens up new possibilities and scope for this catalyst and further research is required to understand the observations.