Self-floating black phosphorous nanosheets as a carry-on solar vapor generator

Abstract Efficient solar vapor generation has provided a feasible way to solve the water shortage in undeveloped and arid areas. However, some photo-thermal materials need additional large-volume support materials being harmful to carry around to obtain float capacity, while suppressing the solar steam generation. Herein, the decrease approach of surface tension was presented for solving the moist-environment degradation behavior of black phosphorus (BP) nanosheets and obtaining the self-floating capacity, thus applying BP nanosheets in solar vapor generation field. With the in situ cross-linking polymerization, trichloro(1H,1H,2H,2H-perfluorooctyl) silane successfully modified BP nanosheets (F-BP). Due to the significantly decreased surface tension, F-BP nanosheets are capable of self-floating easily on water surface and spreading out spontaneously. With assistance of desirable photo-thermal conversion capacity, self-floating BP nanosheets convert the incident photon into local heat, showing excellent vapor generation performance. With simulated sun illumination (1 kW/m2), 238.7 g/m2 BP nanosheets present the evaporation rate of ∼0.9437 kg/(m2•h) and efficiency of ∼64.63±2.3%. Meanwhile, the super-hydrophobicity successfully imparts BP nanosheets with resistance to the deterioration caused by salt precipitation. The carriable F-BP nanosheets are an ideal photo-thermal convertor to produce drinking water, successfully providing a feasible way to solve water shortage in limited condition.