Aerogels Based on MXene Nanosheet/Reduced Graphene Oxide Composites with Vertically Aligned Channel Structures for Solar-Driven Vapor Generation

Abstract

We fabricate MXene-reduced graphene oxide (rGO) hybrid aerogels with vertically aligned channel structures, where the framework of three-dimensional (3D) structures consists of MXene, and rGO nanosheets are attached to the MXene framework. MXene−rGO hybrid aerogels exhibit extremely high light absorption and excellent hydrophilicity, which facilitate vapor generation by harvesting solar energy. Moreover, vertically aligned channel structures dramatically enhance the water transport inside porous light absorbers and substantially reduce the light reflection loss and the heat loss due to multiple internal reflections. Meanwhile, the functional polar groups in the aerogels alter the states of water molecules because the water molecules have strong interactions with the functional polar groups. The coexistence of multiple water states (bound water, intermediate water, and free water) gives rise to the reduction of the vaporization enthalpy and fast water evaporation. The MXene−rGO hybrid aerogels achieve a water evaporation rate of 2.84 kg m −2 h −1 under 1 sun irradiation. The energy transfer efficiency is 96%. We also use the MXene− rGO hybrid aerogels to desalinate the seawater, and desalinated seawater meets the requirements for drinking water.

Anisotropic 3D Aerogel of Graphene Oxide and Poly(Vinyl Alcohol) for Desalination by Interfacial Solar Vapor Generation

“…In the application of ISVG, the direct utilization of solar energy typically relies on all-inclusive evaporators to generate and concentrate heat at the water–air interface, thereby enhancing interfacial water evaporation. , As a result, an ideal ISVG apparatus should meet the following indispensable basic principles: (1) high-performance solar-thermal conversion to maximize the harvest of the energy from sunlight; (2) rational water transport adjustment to ensure sufficient water transport; (3) excellent thermal management to effectively suppress the thermal loss and localize heat to the evaporation position; and (4) efficient salt rejection to avoid salt accumulating at the evaporation site during solar desalination …”

Reusable Floating Spherical Hydrogel Evaporator for Solar Desalination with Salt Mitigation and Contaminant Elimination

“…The scarcity of fresh drinking water is a pervasive global problem affecting people worldwide. , Desalination is considered as an effective, sustainable approach to generate fresh water from seawater and brackish water. , Current desalination technologies are based on reverse osmosis, multistage flash distillation, and electrodialysis, which are expensive. − Solar-induced desalination treatment is a cost-effective as well as eco-friendly approach that uses an interfacial evaporation system to isolate the evaporation interface from bulk water. Heat localization is conducted at the air–water interface to avoid the conduction of heat to the entire water mass and achieve efficient evaporation. ,, The use of various photothermal materials having high light absorption and light-to-heat conversion efficiency concentrates heat on the evaporation surface, which accelerates water transport that balances the evaporation rate. − …”

SCG-Based CNF Aerogels with Oriented and Aligned Porous Structure for Solar Interfacial Desalination

“…The aerogel for SDIE is consisted of photothermal material and skeleton. , The commonly used photothermal materials include carbon-based materials, , metal particles, , and photocatalytic semiconductor, , which transform solar energy to heat for evaporation. The skeleton can catch the photothermal materials and provide the transportation corridor of light and water .…”

“…SDIE is a kind of evaporation technology powered by solar energy where water vaporizes on the surface of the evaporator . Owing to its specific structure, the heat is confined to the interface of photothermal material, which can convert sunlight into thermal energy, so that heat loss is limited and steam generation efficiency is accelerated .…”