Díaz-Marín Carlos D, Masetti Lorenzo, Roper Miles A, Hector Kezia E, Zhong Yang, Lu Zhengmao, Caylan Omer R, Graeber Gustav, Grossman Jeffrey C
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland.
Nat Commun. 2024 Oct 17;15(1):8948. doi: 10.1038/s41467-024-53291-5.
Moisture-capturing materials can enable potentially game-changing energy-water technologies such as atmospheric water production, heat storage, and passive cooling. Hydrogel composites recently emerged as outstanding moisture-capturing materials due to their low cost, high affinity for humidity, and design versatility. Despite extensive efforts to experimentally explore the large design space of hydrogels for high-performance moisture capture, there is a critical knowledge gap on our understanding behind the moisture-capture properties of these materials. This missing understanding hinders the fast development of novel hydrogels, material performance enhancements, and device-level optimization. In this work, we combine synthesis and characterization of hydrogel-salt composites to develop and validate a theoretical description that bridges this knowledge gap. Starting from a thermodynamic description of hydrogel-salt composites, we develop models that accurately capture experimentally measured moisture uptakes and sorption enthalpies. We also develop mass transport models that precisely reproduce the dynamic absorption and desorption of moisture into hydrogel-salt composites. Altogether, these results demonstrate the main variables that dominate moisture-capturing properties, showing a negligible role of the polymer in the material performance under all considered cases. Our insights guide the synthesis of next-generation humidity-capturing hydrogels and enable their system-level optimization in ways previously unattainable for critical water-energy applications.
吸湿材料能够实现诸如大气取水、蓄热和被动冷却等潜在的、可能改变游戏规则的能源-水技术。水凝胶复合材料因其低成本、对湿度的高亲和力和设计的多功能性，最近成为了杰出的吸湿材料。尽管人们为通过实验探索用于高性能吸湿的水凝胶的广阔设计空间付出了巨大努力，但在理解这些材料吸湿特性背后的原理方面仍存在关键的知识空白。这种理解上的缺失阻碍了新型水凝胶的快速发展、材料性能的提升以及器件层面的优化。在这项工作中，我们结合水凝胶-盐复合材料的合成与表征，来开发和验证一种弥合这一知识空白的理论描述。从水凝胶-盐复合材料的热力学描述出发，我们开发了能够准确捕捉实验测量的吸湿量和吸附焓的模型。我们还开发了能够精确再现水分在水凝胶-盐复合材料中动态吸收和解吸的传质模型。总之，这些结果展示了主导吸湿特性的主要变量，表明在所有考虑的情况下，聚合物在材料性能中所起的作用微不足道。我们的见解为下一代吸湿水凝胶的合成提供了指导，并能够以之前关键的水能应用无法实现的方式对其进行系统层面的优化。
