Synergistic Effect Between 0D CQDs and 2D MXene to Enhance the Photothermal Conversion of Hydrogel Evaporators for Efficient Solar Water Evaporation, Photothermal Sensing and Electricity Generation

Abstract

Solar-powered interfacial water evaporation is a promising technique for alleviating freshwater stress. However, the evaporation performance of solar evaporators is still constrained by low photothermal conversion efficiency and high water evaporation enthalpy. Herein, 0D carbon quantum dots (CQDs) are combined with 2D MXene to serve as a hybrid photothermal material to enhance the light absorption and photothermal conversion ability, meanwhile sodium carboxymethyl cellulose (CMC)/polyacrylamide (PAM) hydrogels are used as a substrate material for water transport to reduce the enthalpy of water evaporation. The synergistic effect in 0D CQDs/2D MXene hybrid photothermal materials accelerate the carrier transfer, inducing efficient localized surface plasmon resonance (LSPR) effect. This results in the enhanced photothermal conversion efficiency. The integrated hydrogel evaporators demonstrate a high evaporation rate (1.93 and 2.86 kg m⁻² h⁻¹ under 1 and 2 sunlights, respectively) and low evaporation enthalpy (1485 J g⁻¹). In addition, the hydrogel evaporators are applied for photothermal sensing and temperature difference power generation (TEG). The TEG device presents an efficient output power density (230.7 mW m⁻²) under 1 sunlight. This work provides a feasible approach for regulating and controlling the evaporation performances of hydrogel evaporators, and gives a proof-of-concept for the design of multipurpose solar evaporation systems.