Interfacial Interaction of Monolayer Black Phosphorus/g‐C3N4 Van Der Waals Heterojunction for Efficient Photocatalytic Hydrogen Evolution

The 2D/2D van der Waals heterojunctions have promising photocatalytic applications. However, their interfacial interaction and photocatalytic mechanism are still unclear. Herein, monolayer black phosphorus (BP)/graphitic carbon nitride (GCN) heterojunction photocatalytic hydrogen evolution is systematically investigated using the density‐functional theory method. It is indicated in the results that BP/GCN heterojunction structure distortion and interface interaction change its electronic structure and photocatalytic performance. The hydrogen‐adsorption free energy of BP/GCN heterojunction is −0.28 eV, indicating that the BP/GCN heterojunction has a high catalytic activity for hydrogen production. Calculated Bader charge and Fermi energy level show that a built‐in electric field from BP to GCN forms in its interface. The energy barrier and built‐in electric field promote the recombination of photogenerated electrons in GCN conduction band and photogenerated holes in BP valence band; electrons on the BP conduction band and holes on the GCN valence band are effectively separated in space; and more electrons and holes can participate in redox reactions on the surface. The BP/GCN heterojunction is a type Z heterojunction. Significant improvement in photocatalytic reaction efficiency is attributed to the type Z photocatalytic mechanism and small free energy of hydrogen adsorption. Herein, it is aimed to offer insights into the photocatalytic mechanism of 2D/2D heterojunctions.