B-doping on the electronic structure and photocatalytic properties of g-C3N4/Janus PtSSe heterojunctions: A first-principles study

Abstract

The effect of B doping on the stability, electronic structure, work function, and optical properties of g-C3N4/Janus PtSSe heterojunctions has been investigated based on the density-functional theory plane-wave ultrasoft pseudopotential approach. It is shown that the binding energy of g-C3N4/PtSSe after B doping is negative and has a low layer spacing and lattice mismatch rate. It is stable at a room temperature of 300 K, proving its structural and thermodynamic stability. B-atom doping of g-C3N4/SPtSe and g-C3N4/SePtS heterojunctions leads to the upward shift of the Fermi energy level resulting in a significant reduction of the band gap and significant orbital hybridization. The impurity band near the Fermi energy level easily transfers electrons from the valence band into the conduction band, which makes electron leaps easier. Different built-in electric fields are formed when the g-C3N4 and Se(S) atomic layers are in contact. The reduction of the bandgap after B doping enables the photogenerated electron-hole pairs between the heterojunction interfaces to be better separated under the action of the built-in electric field, which reduces the composite rate of the electron-hole pairs and greatly improves the carrier migration and photocatalytic performance. The absorption and reflection coefficients of g-C3N4/SPtSe-BNC and g-C3N4/SePtS-BNC are the highest and decrease slowly in the visible region, which indicates that they have the optimal photocatalytic performance, and they can effectively broaden the range of light absorption and promote the utilization of light. The introduction of the B–B bonding effectively improves the photocatalytic activity of the heterojunction.