界面太阳能蒸发已成为一种有前景的可持续淡水生产技术，利用可再生绿色能源缓解淡水短缺。水凝胶因其固有的亲水性和保水能力而被认为是界面太阳能蒸发最有效的平台材料。本文首先介绍了水凝胶分子和结构工程方面的进展，以实现高效的界面太阳能蒸发，增加中间水含量，改善热约束和水传输管理，盐弹性和三维结构。随后，研究和讨论了具有额外功能的水凝胶蒸发器的开发，包括刺激响应特性、自愈性、可回收性、消毒和挥发性有机化合物去除能力，以获得更好的水净化性能。总结了水凝胶在新兴的下一代界面太阳能蒸发器中的潜在应用，用于金属离子提取、蒸发冷却和海水淡化以外的发电。目前，该文以“Engineering hydrogels towards next-generation multifunctional interfacial solar evaporators beyond seawater desalination”为题在《Chemical Engineering Journal》上发表。(a) Schematics of three water states in hydrogels (using –OH as a hydrophilic functional group example). (b) Raman spectra with the fitted peaks representing IW and FW in the chitosan/PVA/PPy hydrogel. Reproduced with permission . Copyright 2019 The Authors. (c) Interpenetrating network of PVA/PSS hydrogel with controlled hydration. Reproduced with permission . Copyright 2020 Wiley-VCH GmbH. (d) Schematic illustrations of Hofmeister effect-induced salting-out and salting-in phenomena for hydrogels. (e) Schematics of anti-polyelectrolyte effect-induced IW content increase in the PZH and evaporation performance enhancement. Reproduced with permission . Copyright 2022 Wiley-VCH GmbH. (f) The salt ion-impeding effect in the electronegatively charged hydrogels. Reproduced with permission . Copyright 2023 The Authors.Schematic illustrations of evaporative surface modification strategies. (a) Surface topology-tailored hydrogels for interfacial solar evaporation. Reproduced with permission . Copyright 2019 American Chemical Society. (b) Surface light-trapping texture of TaTe/rGO/agar-agar hydrogels. Reproduced with permission . Copyright 2023 Published by Elsevier B.V. (c) Pited surface structures of hydrogel (upper) and microchannels and small pores enabled salt resistance for the hydrogel evaporator (bottom). Reproduced with permission . Copyright 2023 Elsevier B.V. (d) Schematics of Janus hydrogels with hydrophobic surface layer and hydrophilic bottom layer. Reproduced with permission . Copyright 2023 Published by Elsevier B.V. (e) Island-shaped patchy-surface hydrogels for enhanced solar evaporation. Reproduced with permission . Copyright 2020 The Royal Society of Chemistry.Schematics of 3D hydrogel-based evaporators possessing interconnected structures created by different methods. (a) Hierarchical PVA/PPy hydrogel, with internal gaps, micron channels, and molecular meshes, enabled by freezing-thawing cycles. Reproduced with permission . Copyright 2018 The Authors. (b) The SPJH evaporator with surface topography and internal microchannels templated by air bubbles and ice crystals. Reproduced with permission . Copyright 2021 American Chemical Society. (c) Vertically aligned hydrogel enabled by directional freezing. Reproduced with permission . Copyright 2022 American Chemical Society. (d) The EHSC-VR hydrogel evaporator by directional freezing with enhanced evaporation performance and salt tolerance in brine. Reproduced with permission . Copyright 2022 Wiley-VCH GmbH. (e) The hydrogel evaporator with SHLH structure and its water channels created by nondirectional and directional freezing. Reproduced with permission . Copyright 2024 Wiley-VCH GmbH. (f) Fabrication of PVA/pullulan/MXene nanosheets hybrid hydrogel with directional freezing and salting-out treatment. Reproduced with permission . Copyright 2024 Elsevier B.V. (g) The fabrication process of PVA/AC hydrogel via self-assembled templating. Reproduced with permission . Copyright 2021 Wiley-VCH GmbH. (h) Direct ink writing 3D printing of bionic hydrogel evaporator. Reproduced with permission . Copyright 2024 The Authors.Schematics of salt-mitigating strategies for hydrogel-based ISEs. (a) The balanced ion migration equilibrium between salt ion absorption and discharge upon solar evaporation. Reproduced with permission . Copyright 2018 The Royal Society of Chemistry. (b) Schematic illustrations of “salt-out” and “salt-free” systems. (c) The conical frustum MXene/PVA hydrogel with edge-preferential salt deposition. Reproduced with permission . Copyright 2021 Wiley-VCH GmbH. (d) The rotation mechanism of the spherical hydrogel evaporator upon salt deposition. Reproduced with permission . Copyright 2023 American Chemical Society. (e) The gradient hydrogel consists of three layers and its anti-salt mechanism. Reproduced with permission . Copyright 2021 Elsevier B.V. (f) The working principle of the salt-resistant Janus hydrogel. Reproduced with permission . Copyright under a Creative Commons license CC BY-NC-ND 4.0. (g) The configuration of the Janus ion-selective hydrogel evaporator. Reproduced with permission . Copyright 2023 Wiley-VCH GmbH.Schematic illustrations of energy flow of (a) 2D and (b) 3D solar evaporators. Q is the input solar energy, Q is the convective heat loss, Q is the radiation heat loss, Q is the conductive heat loss, and Q is the environmental energy gain. (c) Infrared images of hydrogels with varied ARs. Reproduced with permission . Copyright 2023 Elsevier B.V. (d) Schematics of the 3D zwitterionic composite hydrogel, where the top part of hydrogel absorbed sunlight and transported water through capillary pumping and volume expansion, while the bottom kept the structure integrity in the foam. Reproduced with permission . Copyright 2024 Elsevier Ltd. (e) The preparation processes of the bionic-gill evaporator. (f) The mechanism of the multidirectional crossflow salt mitigation of the bionic-gill evaporator. (e-f) Reproduced with permission . Copyright 2023 Wiley-VCH GmbH.Illustrations of hydrogels with additional functionalities for solar evaporation. (a) Water uptake and discharge by the thermal-responsive hydrogel. Reproduced with permission . Copyright 2024 American Chemical Society. (b) Borate and hydrogen bonds enabled self-healing hydrogel networks. (c) Photographs of the self-healing process of the hydrogel. (b-c) Reproduced with permission . Copyright 2021 Wiley-VCH GmbH. (d) Self-healing process of HDH hydrogel based on Schiff base bonds. (e) Regeneration of hydrogels through liquefaction-dialysis-regeneration operations. (d-e) Reproduced with permission . Copyright 2023 Wiley-VCH GmbH. (f) Thermo-remodeling of the CS/PNAGA-CNTs hydrogel. Reproduced with permission . Copyright 2022 Elsevier B.V.(a) Schematics of the porous MoS nanoflower-containing hydrogel membrane enabled high-efficiency solar evaporation with anti-bacterial behavior. Reproduced with permission . Copyright 2019 The Royal Society of Chemistry. (b) Spread plate results of E. coli and S. aureus treated with AM/CH and phosphate-buffered saline under one sun irradiation for 1 h. Reproduced with permission . Copyright 2024 American Chemical Society. (c) Mechanism of photo-degradation of VOCs during evaporation. Reproduced with permission . Copyright 2023 Elsevier B.V. (d) Sunflower-inspired vertically aligned structures in the hydrogel evaporator. (e) Photocatalytic degradation mechanism of the MTG heterojunction. (d-e) Reproduced with permission . Copyright 2024 Elsevier B.V. (f) The mechanism of phenol removal by a Fenton reaction. Reproduced with permission . Copyright 2023 Elsevier Ltd.(a) Schematic illustration of solar-driven rapid metal ion removal. (b) The adsorption capacities of a series of metal ions for the poly(HPA-co-AA-co-NVP) hydrogels. (a-b) Reproduced with permission . Copyright 2019 American Chemical Society. (c) Schematics of the fabrication process of GDH. (d) The establishment of an ion migration equilibrium of the GDH system under the solar evaporation process. (c-d) Reproduced with permission . Copyright 2023 The Authors. (e) The Li adsorption mechanism for PPy@HNTs hydrogels. Reproduced with permission . Copyright 2024 Elsevier Ltd.(a) Schematics of the configuration of PAM/alginate/CaCl hydrogel backplate for evaporative cooling of PV panels. Reproduced with permission . Copyright 2023 American Chemical Society. (b) Surface temperatures of the PV panel with and without the hydrogel cooling layer under one sun irradiation. (c) The test set-up for PV panel cooling integrated with a condensation chamber for water collection. (b-c) Reproduced with permission . Copyright 2020 The Authors. (d) Schematic illustrations of the evaporation and regeneration cycle of Li-PAM on PV panels alternating day and night. (e) Surface temperatures of the solar cell with and without Li-PAM cooling layer under one sun. (d-e) Reproduced with permission . Copyright 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (f) Chemical structure of Co@Li-PAM hydrogel, and the interactions between different ions, water molecules, and polymer chains. Reproduced with permission . Copyright 2023 Elsevier Ltd.(a) Schematics of the mechanism of simultaneous solar-driven desalination and salinity-gradient electricity generation. Reproduced with permission . Copyright 2020 Elsevier B.V. (b) The setup of thermo-electricity generation along with evaporation for PVA/CB-based hydrogel evaporator. (c) Open-circuit voltage versus time of the PVA/CB-based hydrogel evaporator under various solar irradiation intensities. (b-c) Reproduced with permission . Copyright 2023 Elsevier B.V. (d) The electricity generation mechanism based on evaporation-induced proton concentration difference. Reproduced with permission . Copyright 2024 Wiley-VCH GmbH. (e) The setup of evaporated brine recycling and the salinity-gradient electricity generation during nighttime. Reproduced with permission . Copyright 2023 The Authors.该文全面概述了基于水凝胶的蒸发器的最新进展和发展，重点介绍了性能增强策略、附加功能以及水凝胶ISE在海水淡化之外的新兴应用。由于其多功能性和溶液加工性，具有额外功能的水凝胶被设计为实现高集水能力、改善水质、长期耐用性和减少环境影响。如，智能水凝胶已被制造并用于太阳能驱动的淡水生产和夜间雾空气收集，从而实现了全天持续的淡水生产。自愈和可回收的水凝胶使ISE设备能够长时间运行，具有耐损伤性和自再生特性。通过加入细菌抑制成分，水凝胶蒸发器可以在没有微生物污染的情况下保持稳定运行。此外，蒸发过程中挥发性有机化合物的去除提高了产出水的纯度。界面太阳能蒸发过程是一个多方面的现象，包括光、温度和相变，以及离子迁移和能量转换过程。利用蒸发过程中产生的废能为蒸发器在金属离子提取、蒸发冷却和发电等领域的应用开辟了新的途径。
总之，水凝胶实现的界面太阳能蒸发是为偏远或离网地区生产淡水的一种有前景的方法。尽管如此，仍存在一些挑战阻碍了水凝胶ISE的商业应用。未来的研究应更多地关注水凝胶蒸发系统的大规模制造和应用，以及新材料和制造技术的发展，以提高性能、稳定性和可扩展性。随着解决上述问题的持续努力，我们设想下一代水凝胶太阳能蒸发器将在应对能源-水关系的全球挑战方面发挥关键作用。
https://doi.org/10.1016/j.cej.2024.157988
