A Fe-Ni-MOF-74@bamboo photothermal evaporator for efficient solar steam generation

Abstract

Solar-driven interfacial steam generation is considered as a promising technology to solve the shortage of fresh water resources by using inexhaustible solar energy. In this field, the challenge comes from the design of an interfacial evaporator with high performance in photothermal conversion, water activation (low evaporation enthalpy) and water delivery ability. Herein, a composite evaporator was prepared by in-situ composition of bamboo and Fe-Ni-MOF-74 and subsequently simple carbonization. In this evaporator, bamboo ensures that water quickly reaches the evaporation interface, and rich hydrophilic groups have the function of activating water molecules. Fe-Ni-MOF-74 enhances photothermal effect due to bimetallic coordination. In addition, the hydrophilic feature and the pore structure strengthen the water activation and water absorption capacity. Meanwhile, carbonization under mild conditions compensates for the light absorption. As an outcome, the evaporator achieves high evaporation rate (3.61 kg m⁻² h⁻¹), high solar-vapor conversion efficiency (153 %), low evaporation enthalpy (1.517 kJ g⁻¹), good stability in saline water and antibacterial function. Furthermore, both seawater and wastewater purified by the evaporator comply with drinking water standards. In the outdoor experiment, the evaporator can collect water of 4.01 kg m⁻² during one daylight. The result highlights great potential of bamboo and MOF composite evaporator for producing fresh water using solar energy.