Round-the-clock interfacial solar vapor generator enabled by form-stable phase change materials with enhanced photothermal conversion capacity

Owing to the intermittent nature of solar energy, the water generation yield of interfacial solar vapor generation during the nighttime is limited. Herein, we propose a phase change material (PCM)-integrated solar vapor generator to address this limitation. Specifically, three types of polyethylene glycol (PEG800, PEG1500, PEG2000)/expanded graphite (EG) form-stable PCMs (FSPCMs) with different thermophysical properties were fabricated. Upon comparing the performances of the three FSPCMs, PEG1500/EG was found to be the optimal specimen and the associated mechanism was discussed in detail. Further, a proof-of-concept evaporator was assembled to find that the all-day mass change of the FSPCM-integrated solar vapor generator was 1.5 times that of the conventional evaporator and 3.0 times that of pure water. Moreover, the mass change of the FSPCM-integrated solar vapor generator during the night was 3.6 times that of the conventional evaporator. Benefiting from the thermal energy storage capacity of the prepared FSPCMs, the FSPCM-integrated solar vapor generator can store the extra energy of the sun in the daytime and achieve continuous vapor generation in both daytime and nighttime. Furthermore, COMSOL simulations indicate that the overall performance of the FSPCM-integrated solar vapor generator can be further improved because the FSPCM module has good scalability. In a word, this study provides a novel strategy to effectively improve the all-day vapor generation yield of interfacial solar vapor generation and inspires further research aimed at the use of thermal storage technology to enable round-the-clock solar vapor generation.