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.