Cu₃BiS₃/MXenes with Excellent Solar-Thermal Conversion for Continuous and Efficient Seawater Desalination

Two-dimensional materials with unique physical and chemical properties have recently attracted widespread attention in the field of solar thermal conversion. However, affected by the Fresnel effect, traditional two-dimensional materials such as MXenes, graphene, transition metal disulfide often have relatively significant light reflection losses at the solid-liquid or gas interface. So how to improve the light absorption of the two-dimensional material performance has become a new challenge in photothermal conversion. Here, we use an improved thermal-injection method to uniformly grow Tricopper(I) Bismuth Sulfide (Cu₃BiS₃, CBS) on the surface of Ti₃C₂ nanosheets in a nonaqueous polar solvent environment. A three-dimensional nanoflower-nanosheet structure CBS-Ti₃C₂ for photothermal conversion has been constructed successfully. Owing to the excellent photothermal performance of Cu₃BiS₃ in the near-infrared region, the good thermal conductivity of Ti₃C₂, and the unique porous structure of the composite material, the composite achieves broadband absorption of light (more than 90% in the visible light region, more than 80% in the near-infrared region), which optical model and finite element simulation have theoretically verified. The composite material has obtained higher solar-to-heat conversion performance than similar material systems, and the steady-state temperature can reach 62.3 °C under 1 sun incident light intensity. CBS-Ti₃C₂ is expected to become a light-absorbing layer material for solar vapor generation devices due to its excellent light-to-heat conversion performance and good material flexibility. It still guarantees a reasonably high steam generation rate (1.32 kg·m^-2·h^-1) even with a thinner material thickness (0.48 mg·cm^-2) and a comprehensive conversion efficiency higher than 90%. Besides, CBS-Ti₃C₂ also exhibits the characteristics of resisting surface salt accumulation, which is conducive to maintaining the long-lasting photothermal seawater evaporation process. The material's electronic structure and the charge transfer process of the heterojunction interface have been studied with the first-principles calculation. The high light absorption performance and good thermal conductivity of the composite material are theoretically explained and supported.