g-C3N4/BiYO3 Composite for Photocatalytic Hydrogen Evolution

g-C3N4/BiYO3 composites were prepared by an electrostatic self-assembly of g-C3N4 and BiYO3 and were used as photocatalysts for photocatalytic hydrogen evolution. The UV-vis DRS revealed that the band gaps of BiYO3 and g-C3N4 were 2.58eV and 2.96 eV, respectively, and the g-C3N4/BiYO3 composites showed stronger visible light absorption than that of g-C3N4 because the composite with BiYO3 served as a narrow bandgap catalyst. Electrochemical impedance spectroscopy (EIS) proved that the g-C3N4/BiYO3 composites exhibited a better electronic transmission capacity and a larger photocurrent than that of g-C3N4 or BiYO3 because the BiYO3 acted as an electron acceptor in the composites. The PL spectra showed that g-C3N4 combined with BiYO3 inhibited the recombination of photo-generated electron holes in g-C3N4 and enhanced the photocatalytic activity for hydrogen evolution. Furthermore, the photocatalytic activities for hydrogen evolution with the g-C3N4/BiYO3 composites were higher than those of the individual g-C3N4 or BiYO3 alone due to the transfer of photogenerated electrons from the conduction band of g-C3N4 to the conduction band of BiYO3 and the transfer of photogenerated holes from the valence band of BiYO3 to the valence band of g-C3N4. The composite with a g-C3N4/BiYO3 mass ratio of 2 showed an optimal hydrogen evolution rate of 37.6 molh(-1)g(cat)(-1), which was 8.4- and 6.4-fold higher than that of g-C3N4 and BiYO3, respectively.