High-performance biomass-based solar-thermal hydrogel based on silkworm excrement for water evaporation and thermoelectric integration application

Abstract

Interfacial solar-driven evaporation technology has received widespread attention. However, there are challenges in achieving efficient photothermal conversion and low cost in its practical application. Biomass materials are derived from renewable and sustainable resources and have potential applications in large-scale production of solar evaporators. In this work, we design a strategy to prepare efficient biomass solar-thermal materials through animal metabolism. Silkworms digest nutrients in mulberry leaves, leaving behind pigments in silkworm excrement (SE) that can form biomass solar-thermal materials. Under the irradiation of 1.0 kW m⁻² simulated sunlight intensity, the surface temperature of SE powder can rise to 50 °C, and the photothermal conversion efficiency can reach 8.94%, which is a good photothermal conversion ability. Using polyvinyl alcohol hydrogel as the water evaporation carrier, a silkworm excrement hydrogel solar evaporator is constructed. Under one sunlight intensity irradiation, the water evaporation efficiency can reach up to 86.65%, with a water evaporation rate of 1.42 kg m⁻² h⁻¹. The low-grade heat generated during the solar-driven evaporation can be effectively used for synergistic water and electricity cogeneration, achieving a voltage of 53.0 mV. This biomass solar-thermal material obtained through animal metabolism is expected to deliver a low-cost, environmentally friendly seawater desalination technology.