Hierarchically Designed Polydopamine@Co3O4–SnO2-Anchored Cellulose Photothermal Sponge for Efficient Interfacial Solar Steam Generation

Solar steam generation is considered to be a modern technology to resolve the drinking water problem of the globe in the near future. The preparation of highly efficient photothermal materials with long life, environmental friendliness, low cost, and the design of the interfacial solar steam generator (ISSG) are the main features of the practical application of ISSG. Herein, we have designed/fabricated a highly efficient polydopamine surface-capped cobalt–tin oxide (PDA@Co3O4–SnO2) heterojunction nanosheets with different ratios of Co3O4–SnO2 optimization, coated on hydrophilic cellulose sponges and utilized as the 3D material in solar steam generation. The hydrophilic photothermal sponges demonstrate excellent light-to-heat conversion and salt discharge properties, which act as self-cleaning tools. The 3D sponges were staked to an adjustable height (5 cm), which demonstrated a maximum evaporation rate of 2.26 kg m–2 h–1 under 1.0 Sun with an energy efficiency of 118.3%. The system was optimized by selecting photothermal materials with excellent hydrophilicity, preventing salt buildup, minimizing heat conduction and radiation, and harnessing environmental energy through an innovative evaporator design. The designed ISSG system is not only cost-effective but has a long life and high efficiency, which have great potential for future practical applications in waste/seawater purification.