Efficient low-frequency microwave absorption and solar evaporation properties of γ-Fe₂O₃ nanocubes/graphene composites

Microwave absorption and solar evaporation have attracted significant interests and great advances have been achieved in the elimination of electromagnetic radiation pollution and production of fresh water. However, enhancing low-frequency microwave absorption properties as well as mass production of cheap solar evaporators with high evaporation rate are still facing many challenges. Herein, γ-Fe₂O₃ nanocubes/graphene (GFC) composites were prepared by a facile one-step solvothermal method. GFC was mixed with paraffin to study its microwave absorption properties. The minimum reflection loss (RL) value of -59.3 dB at 2.4 GHz was achieved by GFC, while the RL value also reached -57.2 dB at 5.12 GHz with a thickness of 5.30 mm. Moreover, under matching frequency and thickness a good absorption performance (RL ≤ -17.2 dB) from 2.00 to 18.00 GHz was obtained, in particular, RL < -30.0 dB in S band and RL < -26.0 dB in C band. Excellent microwave absorption performance of GFC in S and C band is mainly attributed to high impedance matching, which suggests the direction for development of high-efficient low-frequency microwave absorption materials. Interfacial solar evaporator was also prepared by using GFC modified scouring sponge as light absorption layer, which has > 97% absorption in entire solar spectrum range. Its evaporation rate (3.490 kg m^-2h⁻¹) is 5.1 times larger than that of pure water under the same condition, which shows great potential applications in desalination, water purification and energy generation.