An efficient Z-scheme (Cr, B) codoped g-C3N4/BiVO4 photocatalyst for water splitting: A hybrid DFT study

A systematic theoretical research on the geometrical, electronic, optical, charge transfer, and photocatalytic mechanisms of pure, Cr-doped, B-doped, and (Cr, B) codoped g-C3N4/BiVO4 heterostructures using a hybrid density functional approach has been carried out. The face-to-face g-C3N4/BiVO4 composed of two-dimensional materials of g-C3N4 and BiVO4 (010) surface, can introduce a built-in electric field, which promotes interface charge transfer and prevents the electron-hole pair recombination, and causing g-C3N4 monolayer with negative charge and BiVO4 (010) surface with positive charge. Under visible light irradiation, electrons are excited to the conduction band minimum (CBM) of the BiVO4 (010) surface undergoing the hydrogen evolution reaction (HER), while the holes remain in the valence band maximum (VBM) of g-C3N4 monolayer aiding the oxygen evolution reaction (OER). The band edge potentials of BiVO4 (010) surface is higher than that of g-C3N4 monolayer, which ensures a stronger redox reaction potential and therefore belongs to a typical Z-scheme heterostructure. In addition, the Cr or/and B (co)doping introduces the Cr-3d or/and B-2p states to reduce the bandgap and generate impurity levels, thus enhancing solar energy utilization rate and expanding the optical absorption in the visible-light range. The optical absorption intensity of the (Cr, B) codoped g-C3N4/BiVO4 is superior to pure and Cr or B doped g-C3N4/BiVO4, confiriming the synergistic effect of Cr-3d and B-2p states. Thus, this research is helpful to design a novel and potential Z-scheme photocatalyst useful for the photocatalytic water splitting.