All-biobased porous aerogels with low evaporation enthalpy for efficient solar interfacial evaporation

•A solar interfacial evaporator was prepared with all bio-based materials.•The equivalent enthalpy of dark evaporation is as low as 992 J g−1.•The evaporation rate of pure water at one solar intensity reached 3.29 kg m−2 h−1. Solar interfacial evaporation technology has been widely used in the field of water purification due to its low carbon emission and environmental friendliness. However, improving evaporation rates through the structural design of interfacial evaporators remains a challenge. Here, we prepared biodegradable aerogels based on cellulose nanofibers, chitosan, and citric acid, and subsequently prepared a solar evaporator with low enthalpy of evaporation by loading polypyrrole photothermal conversion agent on the aerogel. The evaporator is rich in hydrophilic groups such as hydroxyl, amine, and carboxyl groups, and the hydrogen bonding between them and water molecules changes the state of water adsorbed in the aerogel and reduces the evaporation enthalpy of the adsorbed water. The DSC results show that the evaporation enthalpy of water in the evaporator is as low as 1103 J g−1. As a result, the solar evaporator has a high evaporation rate of 3.29 kg m−2 h−1 for pure water and 3.57 kg m−2 h−1 for 3.5 wt% brine with a solar efficiency of only 86.2 % (1.0 sunlight intensity). Moreover, the evaporator also has a better purification ability for dye wastewater. This research presents a simple and effective strategy for manufacturing high-performance degradable evaporators from biomass materials.