Enhancing optical absorption and charge transfer: Synthesis of S-doped h-BN with tunable band structures for metal-free visible-light-driven photocatalysis

Abstract Two-dimensional materials, especially metal-free two-dimensional materials such as graphene, carbon nitride and boron nitride have attracted significant attention for photocatalysis technology due to their unique charge mobility. Herein, S-doped h-BN with tunable band structure and layer stacking distance has been developed via a facile heat treatment strategy. Compared to the pristine h-BN, the optimized S-doped h-BN exhibited enhanced optical absorption, charge transfer, surface reactivity and hydrophilicity, which greatly improved its ability for photocatalytic degradation of 2,4-DCP. It is clearly demonstrated, by means of various experiments and characterizations, that the bandgap and layer spacing of h-BN can be adjusted by controlling the S doping amount. DFT calculations exposed that the p-orbitals and d-orbitals from sulfur are involved in the formation of the new valence and conduction band edges, which gradually reduced the CB potential, narrowed the bandgap and enhanced the optical absorption property of h-BN. And the shortened layer stacking distance and abundant S doping sites may be the main reason for the promotion of charge mobility and surface reactivity. Through this strategy, h-BN was vested with the ability of visible light response, which provides insights for the modification of other semiconductor materials with wide bandgap, and the study on the compression compaction phenomenon of interlayer stacking distance can open up a new feasible route to enhance charge mobility of other two-dimensional semiconductor materials.