Enhanced photocatalytic activity of BiVO4 by co-grafting of metal ions and combining with CuBi2O4

In order to improve photocatalytic activity of BiVO4, the co-grafting effects of two kinds of co-catalysts for electron and hole separations were examined. At first, stabilization of electrons in BiVO4 by grafting Fe3+ was confirmed by analyzing the formation of O2− and H2O2 as reduction intermediates of O2. When BiVO4 was co-grafted with Fe3+ and CoPi as an electron separator and a hole separator, respectively, its photocatalytic activity for decomposition of gaseous acetaldehyde with visible light (470 nm LED) was enhanced compared to the BiVO4 grafted only by either co-catalyst. This indicated that co-grafting is effective to increase photocatalytic activity because electron and hole were effectively taken out of the BiVO4. Furthermore, by combined with CuBi2O4, a p-type semiconductor, the photocatalytic activity of BiVO4 was also increased. This is because holes and electrons, which were generated in the both semiconductors, were successfully separated in BiVO4 and CuBi2O4, respectively, due to combination of electrons in the BiVO4 with holes in the CuBi2O4. To promote the reaction between electrons in BiVO4 and holes in CuBi2O4, we examined co-grafting effects of two kinds of co-catalyst to the composite by preparing the Cu/CuBi2O4–CoPi/BiVO4 photocatalyst. The photocatalytic activity was further enhanced when it was prepared in a suitable procedure that enables us to graft the reduction and oxidation co-catalysts only at each site.