Cost-effective, scalable fabrication of self-floating xerogel foam for simultaneous photothermal water evaporation and thermoelectric power generation

Three-dimensional (3D) evaporator has become one of the most promising solar absorber/receiver materials for interfacial solar-driven steam generation to efficient global energy and freshwater crises remediation. However, developing 3D evaporators in a green and easy scale-up manner remains a grand challenge. Herein, we pose a cost-effective, scalable, and green foaming method using water as the foaming agent to construct self-floating monolith 3D xerogel foams for synergetic coupling of interfacial solar energy conversion-driven steam genera-tion and low-grade heat-to-electricity conversion. Attributed to its powerful water supply capability, the as -prepared xerogel foam evaporator with porous structure achieves efficient water evaporation without salt accumulation in the course of continuous seawater desalination. Notably, the 3D xerogel evaporator simulta-neously achieves an evaporation rate of 3.39 kg m -2h- 1 and the electric power output of 0.63 W m- 2 under 1 Sun illumination, surpassing great majority of previously reported solar evaporators. In outdoor experiments, the 3D xerogel evaporator realizes a maximum water collecting rate of 1.2 kg m -2h- 1 and an accumulated output amount of 8.9 kg m- 2 during one day. More importantly, six devices connected in series can power small devices like electric fan, calculator and timer. This work provides a cost-effective and easy-to-manufacture vacuum -assisted water-foaming approach for opening up low-cost, high-performance, scalable and durable 3D xerogel evaporators to achieve freshwater and thermoelectric power co-generation in off-grid or remote districts.