Cellulose-based evaporator with dual boost of water transportation and photothermal conversion for highly solar-driven evaporation

Facile fabrication of 3D Janus foams of electrospun cellulose nanofibers/rGO for high efficiency solar interface evaporation

Solar-powered interfacial evaporation is one of the most efficient state-of-the-art technologies for producing clean water via desalination. Herein, we report a novel bio-based nanofibrous foam for high efficiency solar interface evaporation. To this end, a hybrid membrane of cellulose nanofibers/graphene oxide (GO) is first fabricated by electrospinning coupled with in situ layer-by-layer self-assembly technique. After that, the membrane is subjected to a foaming process in an aqueous NaBH4, which effectively transforms the 2D membrane into a 3D foam. This structure can improve the photothermal conversion efficiency and also facilitate the water transport at the gas-water interface. In the meantime, the GO is converted to the reduced GO (rGO) with a higher light absorption efficiency. Finally, one side of the foam is hydrophobically modified via spray-coating with a fluorocarbon resin (FR) to obtain the Janus type 3D foam, namely FR@EC/rGO. The resultant 3D foam combines the functions of solar energy absorption in the upper layer and water pumping capability in the lower layer. It exhibits an extraordinary solar vapor conversion efficiency of 94.2 % and a fast evaporation rate of 1.83 kg m-2 h-1, showing high potential in future seawater desalination.

Tree transpiration-inspired cellulose aerogel with engineered cold-evaporated surface for promoting structural stability and minimizing energy loss

Solar-driven evaporation technology could significantly relieve the fresh-water crisis in the world. However, several problems, such as poor structural stability, low photothermal conversion capacity, and single heat source of traditional evaporators limited the promotion of fresh-water production efficiency. Herein, inspired by tree transpiration, we report a hydrophilic three-dimensional (3D) cellulose-based evaporator similar to the root of a tree, which can pump the bottom water to the evaporation surface for vapor generation. The aldehyde-based cellulose nanocrystals/ethylene imine polymer (ACP) aerogel was developed through Schiff base reaction to enhance the chain entangle capacity of the cellulose nanocrystals (CNCs) aerogel in water. Coating the ACP aerogel with lignin-derived photothermal material created the double-layered solar-driven evaporator (ACP-7LM), achieving a remarkable surface temperature of 35.9 °C in water under 1 sun irradiation for 1 h. The ACP-7LM exhibited an impressive evaporation rate of 1.60 kg m-2 h-1, leveraging its structural stability and excellent photothermal conversion. Increasing the cold evaporation surface (adjusting exposure height from 0 cm to 4 cm) of ACP-7LM aerogel maintained a lower temperature compared to ambient temperature on the side surface during evaporation, which harvest heat energy from environment and minimize energy loss. This enhanced environmental heat absorption boosted the ACP-7LM's evaporation rate to 3.76 kg m-2 h-1, a 2.35-fold increase over the ACP-7LM (0 cm). This solar-driven evaporator offers an efficient, innovative approach to elevate evaporation rates and address the global water crisis by simultaneously enhancing heat absorption capacity and photothermal conversion efficiency.

Derivation of porous cellulose propionate using hydrated hydroxyl groups and hydraulic pressure

This study aimed to enhance the thermal stability of microporous separators by introducing cellulose propionate (CP) as an innovative polymer matrix material, supplemented with glycerin as an additive. CP/glycerin composite membranes were created using hydraulic pressure techniques to reinforce essential separator properties. SEM analysis unveiled interconnected pores crucial for efficient ion transport, initiating water flux measurements at 5 bar. These measurements showcased improved mechanical strength, resulting in a porosity of 74.1 %. FT-IR spectroscopy illustrated CP-glycerin interactions, inducing plasticization and facilitating pore formation. Thermal Gravimetric Analysis (TGA) demonstrated superior thermal stability in CP/glycerin composite membranes compared to cellulose acetate (CA). Differential Scanning Calorimetry (DSC) revealed a slight reduction in thermal stability within a specific temperature range due to glycerin-induced plasticization effects. Nonetheless, the melting temperature (Tm) of CP/glycerin membranes increased to 188.4 °C, indicating heightened stability at elevated temperatures. Despite pressure-induced pore formation, CP/glycerin membranes exhibited enhanced thermal stability, suggesting reinforced molecular interactions. Overall, this study introduces a novel CP/glycerin composite membrane featuring improved thermal stability, enhanced strength, and controlled pore structures essential for efficient lithium-ion battery applications.