Construction of unique floating Bi2WO6/g-C3N4 S-scheme heterojunction to promote photocatalytic activity

Inspired by the floating and photosynthesis of algae and corals in the marine ecosystem, a floating photocatalytic system with an S-scheme heterojunction was constructed using melamine sponge as the backbone and Bi2WO6/g-C3N4 as the active components. This system has the advantages of easy availability of raw materials, low cost, simple preparation, easy recovery, and full utilization of solar light, addressing the disadvantages of powdered materials such as difficulty in recovery, susceptibility to external environmental factors, and inactivation. The unique floating structure allows photocatalytic reactions to occur at the interface between water and air, increasing the utilization rate of air O2. Taking BWO/FCN materials as an example, the layered BWO and g-C3N4 were attached to the carbonized melamine sponge backbone using a direct thermal shrinkage method and hydrothermal treatment, forming an S-scheme heterojunction with a suitable band gap. Under visible light irradiation, after 90 min of reaction, the degradation rate of TC reached 98.2 %, with excellent stability and recyclability. Using in-situ XPS, we tested the electron transfer rules in the BWO/FCN heterojunction and demonstrated the successful formation of the S-scheme heterojunction. The structure and properties of the material were characterized and analyzed using SEM, TEM, UV–vis, electrochemical testing, ESR, and other techniques. Finally, the possible ways of TC degradation and the eco-toxicity of intermediate products and the reduction process of product toxicity were analyzed. This study provides a new perspective for researching floating materials and S-scheme heterojunctions, laying a foundation for future environmental governance and energy conversion research in this field.