An economically scalable sponge-based evaporator with multiscale gradient pores and lowered enthalpy for solar-powered water production via efficient steam generation

Abstract

Although interfacial solar evaporation presents a viable approach to alleviate water scarcity, the absence of cost-effective and scalable evaporators remains a critical barrier to implementation. Herein, we developed an economically scalable sponge-based evaporator (CAP) with multiscale gradient pores and lowered enthalpy for solar-powered water production via efficient steam generation. CAP was fabricated by cross-linking ultralow-cost carbon black (CB) into a sponge framework using sodium alginate-Ca2⁺, where the CB serves as the photothermal conversion material. Under 1 kW m⁻2 irradiation, CAP achieved an exceptional evaporation rate of 1.69 kg m⁻2h⁻1 with a photothermal conversion efficiency of 96.2%. This outstanding performance originates from the synergistic effect between CB’s excellent broadband light absorption and the sponge framework ’s unique gradient pore structure. Particularly, an optimized CB/SA mass ratio of 0.8:1 successfully constructed hierarchical capillary networks enabling efficient water transport and low evaporation enthalpy. Mechanical tests and cycling experiments confirmed CAP’s structural stability. Furthermore, the evaporator demonstrated superior performance in seawater desalination, heavy metal removal, and organic dye wastewater purification. These findings indicate that CAP possesses significant application potential, providing a feasible pathway toward scalable implementation of solar evaporation technology.