Sandwiched solar interfacial evaporation system: Integrating phase change material/hydrogel/NiCo2O4 nanoflower for superior desalination

Solar-driven interfacial evaporation is a kind of sustainable and eco-friendly method of water treatment to alleviate the global water crisis. Here we demonstrate a novel sandwiched solar interfacial evaporator integrating phase change material (PCM), sodium alginate hydrogel (SA), and NiCo2O4 nanoflower featuring superb evaporation and glorious thermal energy management to achieve efficient energy utilization and long-term evaporation stability. After being combined with filter paper, NiCo2O4 nanoflower composites are adopted as the light absorber on the top layer, which can achieve an absorption of about 96.5 % in the full spectral range. SA hydrogel has been used as an intermediate layer for rapid water supply to the evaporation interface and to prevent salt deposition. Under one sun irradiation (1 kW m−2), the evaporator exhibits a high evaporation rate (1.94 kg m-2h−1) and excellent endurance in the treatment of high salt-concentration water. In particular, benefiting from the rational combination of PCM, the water production reached up to 12.13 kg m−2, which is 2.23 kg m-2higher than that of the evaporator without PCM under natural solar irradiation for 9 h. This work presents a promising concept for maximally utilizing intermittent solar irradiation energy and prolonged salt-free deposition desalination.