Cellulose-derived hydrogel with low vaporization enthalpy enables highly efficient solar steam generation

Cellulose has drawn much attention in the field of interfacial solar steam generation (ISSG) due to its advantages of renewability, abundant availability, and hydrophilicity. However, the hydroxyl groups of cellulose form weak hydrogen bond interaction with water, resulting in high evaporation enthalpy and thereby low evaporation rate. Herein, carboxylic acid groups possess of strong interaction with water were introduced into cellulose hydrogel to fabricate efficient ISSG. The carboxylated cellulose hydrogels feature excellent hydrophilicity and water supply capacity because of its rich hydroxyl groups, carboxyl groups, and pore structure. More importantly, the carboxyl groups can effectively weaken the hydrogen bond interactions between water molecules, resulting in larger intermediate water contents that reduced water vaporization enthalpy as small as 1198 J g^-1. Consequently, the evaporator shows a remarkable evaporation rate of 3.68 kg m^-2 h^-1 under one sun irradiation when using bamboo carbon black as the photothermal material. Moreover, the evaporator exhibits superior seawater and sewage purification capabilities, along with outstanding salt resistance. This work presents an advisable strategy of cellulose structure design for interfacial solar evaporation.