Simple Preparation of Waste Boron Nitride/C₃N₄ Composites and Simulated Solar Photocatalytic Performance

In industrial production, the preparation of cubic boron nitride (cBN) under high temperature and pressure wastes a large amount of unreacted hexagonal boron nitride (hBN). This study aims to use this BN waste (wBN) as a raw material, composite it with g-C₃N₄ to construct wBN/g-C₃N₄ composites, and apply the composites in the field of photocatalysis. wBN/g-C₃N₄ composites were prepared by simple calcination using wBN and ammonium cyanide as raw materials. Results showed that a heterogeneous structure was formed in the composite photocatalyst, with a decrease in its bandgap width and a significant increase in its ability to absorb light. The simulated sunlight photocatalytic activity of composite photocatalysts was significantly better than that of single wBN or g-C₃N₄. The photocatalytic performance of B2 sample, composed of a 4:3 ratio of wBN and melamine in the raw materials, demonstrated the highest efficiency. Under simulated solar illumination, it was capable of degrading 99.3% of MB within 60 min. The experimental results with additional capture agents indicated that the main reactive species of the composite photocatalyst were superoxide radicals (·O₂⁻) and holes (h⁺).