Highly efficient solar-thermal thermoresponsive hydrogel based on a fullerene derivative for water purification and energy harvesting†

Solar-thermal evaporators play crucial roles in the field of interfacial solar-driven water evaporation. However, the traditional solar-thermal evaporators are generally unable to achieve all-in-one highly effective thermal management and water transport, which limits their practical application in desalination. Herein, [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) is reported as a classical photovoltaic acceptor material. Compared with the traditional carbon materials, PCBM possessed solution processability because of its ester functional group. Meanwhile, the photothermal conversion efficiency of PCBM reached 14.65%. In addition, poly(N-isopropylacrylamide) (PNIPAm) and polyvinyl alcohol (PVA) were blended as the carrier, resulting in the formation of a solar-thermal thermoresponsive hydrogel (STT/H) based on PCBM. STT/H was beneficial for all-in-one thermal management and water transport, purifying significant amounts of water in a short period compared with conventional hydrogels owing to its temperature deformation. The evaporation rate of STT/H reached 1.46 kg m⁻² h⁻¹ under 1.0 kW m⁻² simulated solar irradiation. Moreover, a temperature difference was produced between STT/H and cold water during the solar-driven water evaporation, and the waste heat generated was effectively converted into electricity by assembling STT/H with a thermoelectric module, realizing water-electricity cogeneration. A water evaporation rate of 0.93 kg m⁻² h⁻¹ and an output voltage of 57.9 mV were simultaneously obtained under one sunlight irradiation. In this study, solution-processable solar-thermal materials based on a fullerene derivative was extended to the field of interfacial solar-driven water evaporation. Furthermore, a novel thermoresponsive double-network hydrogel was proposed, providing a new strategy for solving the problem of seawater desalination.