Metal-Free 2D/2D Phosphorene/g-C₃ N₄ Van der Waals Heterojunction for Highly Enhanced Visible-Light Photocatalytic H₂ Production

The generation of green hydrogen (H₂ ) energy using sunlight is of great significance to solve the worldwide energy and environmental issues. Particularly, photocatalytic H₂ production is a highly promising strategy for solar-to-H₂ conversion. Recently, various heterostructured photocatalysts with high efficiency and good stability have been fabricated. Among them, 2D/2D van der Waals (VDW) heterojunctions have received tremendous attention, since this architecture can promote the interfacial charge separation and transfer and provide massive reactive centers. On the other hand, currently, most photocatalysts are composed of metal elements with high cost, limited reserves, and hazardous environmental impact. Hence, the development of metal-free photocatalysts is desirable. Here, a novel 2D/2D VDW heterostructure of metal-free phosphorene/graphitic carbon nitride (g-C₃ N₄ ) is fabricated. The phosphorene/g-C₃ N₄ nanocomposite shows an enhanced visible-light photocatalytic H₂ production activity of 571 µmol h^-1 g^-1 in 18 v% lactic acid aqueous solution. This improved performance arises from the intimate electronic coupling at the 2D/2D interface, corroborated by the advanced characterizations techniques, e.g., synchrotron-based X-ray absorption near-edge structure, and theoretical calculations. This work not only reports a new metal-free phosphorene/g-C₃ N₄ photocatalyst but also sheds lights on the design and fabrication of 2D/2D VDW heterojunction for applications in catalysis, electronics, and optoelectronics.