MnO2/Poly-L-lysine Co-decorated Carbon Fiber Cloth with Decreased Evaporation Enthalpy and Enhanced Photoabsorption/Antibacterial Performance for Solar-Enabled Anti-fouling Seawater Desalination

Solar-driven seawater evaporation is a potential strategy for mitigating global freshwater shortage, but its application is hindered by the photothermal membranes with high evaporation enthalpy, unsatisfactory photoabsorption, and easy contamination by microorganism. To solve these problems, herein we reported the design of manganese oxide/poly-L-lysine co-decorated carbon-fiber cloth (CFC) with decreased evaporation enthalpy and enhanced photoabsorption/antibacterial performance. Manganese oxide (MnO₂) nanosheets (thickness: 10–30 nm, diameter: 400–450 nm) were grown in situ on the CFC surface by a hydrothermal method, and then the nanosheet surface was further decorated with poly-L-lysine (PLL) by the electrostatic adsorption. Co-decoration of MnO₂/PLL confers the conversion of hydrophobic CFC to superhydrophilic CFC/MnO₂/PLL, accompanied by the reduction of the evaporation enthalpy of bulk water to 2132.34 kJ kg⁻¹ for CFC/MnO₂/PLL sample. Such CFC/MnO₂/PLL exhibits a strong photoabsorption in wide range (280–2500 nm) with an absorption efficiency of 97.8%, due to the light-trapping effects from hierarchical structures. Simultaneously, CFC/MnO₂/PLL has excellent antibacterial performance toward E. coli (99.1 ± 0.2%) and S. aureus (98.2 ± 0.5%) within 60 min in the dark, due to the electrostatic interaction between the bacterial cell membrane and PLL. Subsequently, CFC/MnO₂/PLL was hung between the seawater tank and empty tank to construct a hanging evaporator. Under 1.0 kW m⁻² light irradiation, CFC/MnO₂/PLL shows a preeminent evaporation rate of 2.20 kg m⁻² h⁻¹. Importantly, when germy NaCl solution is evaporated, there is no solid-salt accumulation and bacteria contamination on CFC/MnO₂/PLL surface during the long-time test (12 h), conferring long-term anti-fouling seawater evaporation. Hence, this work provides new possibilities in the rational design of photothermal fabrics for solar-enabled efficient anti-fouling seawater desalination.

Graphical Abstract