g-PAN/g-C3N4 encapsulated Cu nanoparticles with photocatalytic properties and high stability prepared using a two-step sintering method

Abstract

Copper-based photocatalysts have attracted much attention because of their great prospects in photochemical conversion. However, the preparation of highly stable copper-based photocatalysts is a challenge. In this study, copper nanoparticles (Cu NPs) wrapped in graphitized polyacrylonitrile (g-PAN) were prepared by a two-step sintering method. Even if Cu@g-PAN is placed in the air for one month, the Cu NPs were still not oxidized. Furthermore, we succeeded in further introducing graphitized carbon nitride (g-C₃N₄) into the g-PAN shell structure, which was confirmed using a Scanning Transmission Electron Microscope (STEM), FT-IR, and UV-Vis absorption spectra. Cu@g-PAN/g-C₃N₄ can degrade 88.61% of methylene blue (MB) in one hour, showing a higher catalytic activity than Ag@g-PAN/g-C₃N₄ (55.18%). XPS and Auger electron spectroscopy tests of catalyzed Cu@g-PAN/g-C₃N₄ show that Cu is not oxidized. We have proposed a possible mechanism for charge separation and transformation in the Cu@g-PAN/g-C₃N₄ composites to explain the enhanced photocatalytic performance. This work provides a new method to protect Cu NPs and demonstrates the prospect of rational design of copper-based photocatalysts with high stability and efficiency.