Theoretically guiding the construction of a novel Cu2O@Cu97P3@Cu3P heterojunction with a 3D hierarchical structure for efficient photocatalytic hydrogen evolution

Abstract

Using photocatalysis to produce clean H₂ energy has been considered as one of the ideal strategies to alleviate the energy crisis and environmental pollution. In this work, the density functional theory (DFT) calculation was used as a guide to determine the experimental scheme of surface modification of Cu₂O with Cu₃P. With Cu₂O as the core and Cu₃P as the shell, the precursor was constructed by electrostatic self-assembly at first. After secondary calcination, Cu₉₇P₃ was formed from the compact interface between Cu₂O and Cu₃P, thus the 3D hierarchical structure of Cu–O–P(Cu₂O@Cu₉₇P₃@Cu₃P) was successfully constructed. The generation of Cu₉₇P₃ significantly increases the photocatalytic H₂ production of Cu₂O@Cu₉₇P₃@Cu₃P under visible light irradiation. The photocatalytic activity of the composite with optimal ratio increased about 17 times as much as that of pure Cu₂O. The separation and transportation efficiency of its photogenerated charges has been significantly improved. The 3D hierarchical core–shell structure is not only beneficial to strengthen the interface contact between different semiconductors but also to improve the transferability of photogenerated electrons. Through a series of experimental results, the strategy has proved to be successful that Cu₃P was introduced onto the surface of the Cu₂O octahedron to change the adsorption free energy of H atoms, reduce the overpotential of hydrogen evolution, and increase the active sites of hydrogen production. At the same time, the isolated interfaces are integrated by calcination to obtain Cu₉₇P₃ bridged substances derived from the interfaces. The presence of Cu₉₇P₃ establishes a new fast channel for electron flow between semiconductors, significantly accelerates the transfer of electrons, and ultimately improves the performance of photocatalytic hydrogen evolution. This work provides new insights into the design and flexible synthesis of inexpensive copper-based nano-photocatalysts.