Photothermal membrane fabricated by Chinese ink nanofluid for solar bi-directional interface evaporation

Solar steam generation has the potential to address the dual challenges of freshwater shortage and global energy crisis. Traditional photothermal membranes still face challenges such as low evaporation efficiency and poor durability. Inspired by the outdoor drying of clothes, the study reports a new bi-directional interface evaporator by vertically placing a photothermal membrane. The heat transferred to the opposite side of the photothermal membrane via thermal conduction is almost entirely reused. And the bi-directional interface evaporator can achieve an evaporation rate of 1.91 kg m⁻²h⁻¹ under 1 kW/m⁻²(−|-) solar irradiation. Consequently, the evaporation efficiency of the vertically placed evaporator has increased by 35.5 % compared to traditional horizontally placed evaporators due to the bi-directional evaporating effect. The durability of the photothermal membrane made from Chinese ink nanofluids solution prepared by grinding ink ingots can be effectively improved. Consequently, the photothermal membrane maintains a stable evaporation rate over 10 cycles. Therefore, these advantages result in an efficient, durable, and straightforward photothermal membrane for clean water production.