Mildly Peeling Off and Encapsulating Large MXene Nanosheets with Rigid Biologic Fibrils for Synchronization of Solar Evaporation and Energy Harvest

Efficient and nondestructive liquid exfoliation of MXene with large lateral size has drawn growing research interest due to its outstanding properties and diverse potential applications. The conventional sonication method, though enabling a high production yield of MXene nanosheets, broke them down into submicrometric sizes or even quantum dots, and thus sacrificed their size-dependent properties, chemical stability, and wide applications. Herein, rigid biological nanofibrils in combination of mild manual shake were found to be capable of peeling off MXene nanosheets by attaching on MXene surfaces and localizing the shear force. With comparison to sonication, this efficient and nondestructive exfoliation approach produced the MXene nanosheets with the lateral size up to 4-6 μm and a comparable yield of 64% within 2 h. The resultant MXene nanosheets were encapsulated with these biological fibrils, and thus enabled super colloidal and chemical stability. A steam generation efficiency of ∼86% and a high evaporation rate of 3.3 kg m-2 h-1 were achieved on their aerogels under 1-Sun irradiation at ∼25 °C. An evaporation rate of 0.5 kg m-2 h-1 still maintained even at the atmospheric temperature of -5 °C. More importantly, an electricity generation up to ∼350 mV also accompanied this solar evaporation under equivalent 5-Sun irradiation. Thus, this fibrous strategy not only provides an efficient and nondestructive exfoliation method of MXene, but also promises synchronization of solar-thermal evaporation and energy harvest.