Construction of a Three-Dimensional Interpenetrating Network Sponge for High-Efficiency and Cavity-Enhanced Solar-Driven Wastewater Treatment

It is well known that the photothermal conversion performance of solar-driven interfacial water evaporation systems is known to have a stronger photothermal conversion performance than suspended water evaporation systems due to their relatively strong ability to suppress overall heat loss. Natural polymer chitosan and gelatin can form a three-dimensional interpenetrating network (IPN) sponge to provide an interface for water evaporation due to strong hydrogen bonding and electrostatic attraction interaction. However, the lack of effective light absorption, the intrinsic short lifetime, and the poor photothermal conversion greatly compromise their steam generation performance. Here, we fabricated a chitosan/gelatin-based IPN sponge incorporated with melanin-coated titania hollow nanospheres (CG@MPT-h) as a solar thermal converter, which is designed to exhibit a unique cavity structure and vertical channels. The cavity structure of melanin-coated titania acts as a solar thermal transducer, while the chitosan/gelatin-based IPN sponge acts as a single-pass water pump. A water hyacinth-inspired evaporation system shows outstanding steam generation performance, and the highest steam generation rate was 3.17 kg m^-2 h^-1 under a 2.5 sun illumination because of the cavity enhancement effect, far above TiO₂ particles and reported photo-thermal conversion materials. More importantly, the embedding of MPT-h nanoparticles in the IPN sponge effectively inhibits the growth of bacteria in the vertical channels, resulting in an antibacterial solar-driven water evaporator. This advanced sponge provides a cost-effective and practical sustainable energy technique for solar-driven wastewater treatment.