A salt-resistant solar evaporator with organic diradicaloids as photothermal materials for efficient and persistent desalination

Abstract

Interfacial solar water evaporation (ISWE), a new water treatment technology, exhibits promising applications in the fields of fresh water and sustainable energy. Preventing surface salt accumulation while maintaining high solar-thermal conversion performance is a critical issue in ISWE-based desalination. Herein, we report a new strategy to design a salt-resistant solar evaporator, namely construction of a hydrophilic solar-thermal evaporator featuring capillary action enabled by loading organic photothermal materials onto a biomass substrate. Using diradicaloid boron-doped molecular carbons as photothermal materials, the as-prepared solar evaporators exhibit a temperature rise to 74 °C under 1 kW m⁻² simulated solar irradiation. The solar-to-vapor efficiency is up to 93%, and the rate of water evaporation reaches 1.36 kg m⁻² h⁻¹. Importantly, this evaporator can sustain long periods of evaporating water without surface salt accumulation from the outdoor evaporation of seawater for 14 days. Moreover, the waste heat may be used to generate electricity and collect minerals at the end of the device in the evaporation process. Therefore, the efficient and persistent water evaporation without salt accumulation is achieved for this salt-resistant solar evaporator, which will promote the development of the ISWE technology for solar desalination and other applications.