CuS Hollow Nanospheres/Cellulose Composite Film as a Recyclable Interfacial Photothermal Evaporator for Solar Steam Generation

Effective utilization of solar energy for the production of thermal energy is regarded as one of the most sustainable ways to conquer the growing global energy crisis. Photothermal conversion at the water–air interface is considered to be a promising route for steam generation, distillation, and desalination. However, most of the interfacial photothermal evaporators often require optical concentrators and complicated systems with multiple components, leading to poor efficiency and high cost. Herein, an extremely simple and low‐cost interfacial heating film for highly efficient solar steam generation is introduced. The composite film is composed of a viscose cellulose film loaded with CuS hollow nanospheres. The CuS/cellulose composite film, fabricated by a solvothermal method process, serves as an efficient solar absorber (>94%), vapor channel, and thermal insulator (the thermal conductivity is 0.06 W m −1 K −1 ), leading to an efficiency of 85% under solar irradiation (1.0 kW m −2 ), which represents a concrete step for solar steam generation to alleviate the global water scarcity.