Dual waste-derived 3D solar evaporator with vertically aligned channels for efficient solar-driven desalination, wastewater purification, and thermoelectricity generation

Solar-driven interfacial evaporation (SDIE) represents a sustainable pathway for the co-production of freshwater and electricity, offering a promising solution to global water scarcity and energy deficits. However, the development of low-cost, easily fabricated, highly efficient, and salt-resistant water-electricity cogeneration systems remains a significant challenge. Herein, we fabricate a robust and cost-effective 3D solar evaporator (3D-CSC/SA@CF) by integrating corn straw-derived carbon (CSC), discarded cigarette filters (CF), and sodium alginate (SA) hydrogel. In this configuration, the CF scaffold serves as a hydrophilic, quasi-aligned porous substrate for rapid water transport, while the CSC layer functions as an efficient broadband solar absorber, endowing the evaporator with a high light absorption of 97.15 %. Benefiting from its abundant hydrophilic groups and rationally designed porous structure, the evaporation enthalpy is significantly reduced to 851 J g −1 —far below that of pure water. As a result, the evaporator achieves an evaporation rate of 4.52 kg m −2  h −1 under one-sun irradiation (1 kW m −2 , AM 1.5G), with a corresponding solar-to-vapor efficiency of 97.01 %. The system also exhibits remarkable salt-rejection performance, maintaining a stable evaporation rate of 3.22 kg m −2  h −1 in 20 wt% NaCl brine without salt accumulation, and effectively removes heavy metal ions, organic dyes, and antibiotics from simulated wastewater. Furthermore, we construct an integrated thermoelectric cogeneration system based on the evaporator, which delivers a maximum output power density of 307.1 mW m −2 under 1 sun illumination. This work not only demonstrates a sustainable waste-to-resource strategy but also provides a feasible and scalable approach to multifunctional hydro-energy cogeneration, highlighting its potential for practical applications in remote and resource-limited regions.