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

Using photocatalysis to produce clean H-2 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 H-2 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.