Three-dimensional wood-based evaporator with asymmetric wettability for efficient solar interfacial evaporation

Desalination with solar-driven photothermal evaporators is an efficient approach for freshwater scarcity. Here, a three-dimensional wood-based evaporator (Fe 3 O 4 -C-BW) was prepared by in situ growth of Fe 3 O 4 nanoparticles on basswood, which was carbonized on the surface of an annual ring. The carbon component synergized with the Fe 3 O 4 to enhance the capture absorption of sunlight, resulting in 94 % light absorption. The natural pores inherent in the basswood ensure a rapid water supply. The evaporated surface exhibits hydrophobicity due to carbonation, accelerating the nucleation of vapor bubbles. To further optimize the vapor release process in the evaporator, an applied magnetic field was introduced to induce a perturbing behavior of the Fe 3 O 4 particles, thus reducing the stripping diameter of the vapor bubbles as well as increasing the heat flow density of the vapor bubbles. It is under 1 sun irradiation that the Fe 3 O 4 -C-BW exhibited an outstanding evaporation rate (1.50 kg m −2 h −1 ) and efficiency (94.5 %). Fe 3 O 4 -C-BW rapidly heated up to 48.3 °C within 20 min, which is consistent with the numerical simulation result (46 °C). The evaporator was operated continuously for 6 h under real seawater conditions with little degradation in performance and good stability. While producing fresh water efficiently, the Fe 3 O 4 degraded printing and dyeing wastewater by photocatalytic degradation with 100 % decolorization. Thus, the three-dimensional wood-based evaporator Fe 3 O 4 -C-BW with asymmetric wettability is not only able to produce fresh water from seawater quickly and continuously, but also has a highly efficient wastewater purification function, which is a reasonable example of a dual-function evaporator design. • 3D wood-based evaporator for desalination and wastewater purification. • Magnetic Fe 3 O 4 nanoparticles disturb the steam growth. • Evaporator achieves 94.5 % evaporation efficiency under 1 sun.