近期，海南大学南海海洋资源利用国家重点实验室海洋动力资源方向，黄玮副研究员“深海水淡化与综合利用”团队在《ACS Applied Materials & Interfaces》发表了一篇名为“Hierarchical Natural Pollen Cell-Derived Composite Sorbents for Efficient Atmospheric Water Harvesting”的研究论文，中文译文为“分级的天然花粉细胞衍生的复合吸附剂用于高效的大气水捕获”。

Recently, Associate Research Professor We Huang and the team fellows in his research team “Deep Ocean Water Desalination and Comprehensive Utilization” of the State Key Laboratory of Marine Resources Utilization in South China Sea of Hainan University published a paper entitled “Hierarchical Natural Pollen Cell-Derived Composite Sorbents for Efficient Atmospheric Water Harvesting” in ACS Applied Materials & Interfaces.

面对日益增长的全球人口，淡水资源短缺正成为威胁人类生存的重大挑战。据估计，大气中含有地球上所有河流水量的6倍。大气水主要以水汽和水滴的形式存在，通过全球水文循环不断补充。同时，由于消除了农业污染、大气污染物、工业和矿山矿渣等污染源，这种循环增加了额外的好处。在早期，收获大气水的主要方法是捕雾和收集露水。事实上，雾捕集的性能高度依赖于空气的高相对湿度（RH），而露水收集在低RH下运行时消耗巨大的能量，甚至在温度低于露点时由于结冰而失去能力。目前，基于吸附的大气水捕获（AWH），包括从空气中捕获水蒸气的吸湿剂和释放水的光热过程，已成为一种有前途的清洁水生产方法。虽然吸湿剂的再生也会消耗额外的能源，但能源来源可能是低品位能源，如太阳能或废热，这使得它在贫困、干旱和离网地区是可行和负担得起的。

Freshwater scarcity is becoming a critical challenge threatening human survival, facing the growing global population. It was estimated that the atmosphere contains 6 times the amount of water in all rivers on the earth. Atmospheric water exists mainly as water vapor and water droplets, which is continuously replenished through the global hydrological cycle. In the meantime, this circulation adds additional benefits as the pollution sources such as agricultural pollution, atmospheric pollutants, and industrial and mine slag are removed. In the early times, the main methods to harvest atmospheric water were fog trapping and dew collection. As a matter of fact, the performance of fog trapping is highly dependent on the high relative humidity (RH) of air, while dew collection consumes tremendous energy when operating at low RH, or even loses its capacity when the temperature is below the dew point, as a result of freezing. Currently, sorption-based atmospheric water harvesting (AWH), which includes moisture sorbents to harvest water vapor from the air and photothermal processes to release water, has emerged as a promising method for clean water generation. Though the regeneration of moisture sorbent also consumes additional energy, the energy source could be low-grade energy such as solar energy or waste heat, which makes it feasible and affordable in poverty and arid and off-grid regions.

在这里，受树木蒸腾作用的启发，开发了一种基于天然油菜花粉细胞衍生的LiCl@花粉细胞-聚吡咯（LiCl@PC-PPy）吸附剂用于AWH。

The authors develop a nature-inspired design concept of an AWH device based on natural rape pollen cells derived LiCl@pollen cell–polypyrrole (LiCl@PC-PPy) sorbent.

首先对天然油菜花粉细胞进行预处理，以除去果胶，氨基酸，维生素，蛋白质和其他物质，形成分层中空结构花粉细胞（PC）前体。PC颗粒的中空结构可以提供足够的空间来储存吸湿剂和吸附的水蒸气，并为潮湿的空气运输保留足够的颗粒间通道。PPy光热材料在PC颗粒的骨架上原位聚合。LiCl@PC-PPy吸附剂是通过将LiCl吸湿剂浸润到PC-PPy细胞笼而获得。PPy太阳能吸收剂的均匀生长提高了PC颗粒的粗糙度，有利于增强光捕获，增加水分子的吸附位点，而LiCl的负载增加了亲水性和吸附能力。

The natural rape pollen cells are first pretreated to remove the pectin, amino acids, vitamins, proteins, and other substances, forming the hierarchical hollow structured pollen cell (PC) precursor. The hollow structure of PC particles can provide sufficient space to store hygroscopic agent and adsorbed water vapor, and preserve enough interparticle channels for the transport of moist air. The PPy photothermal material is in situ polymerization on the skeleton of the PC particle. The LiCl@PC-PPy sorbent is obtained by infiltrating the LiCl hygroscopic agent into the cages of PC-PPy. The uniform growth of the PPy solar absorber improves the roughness of the PC particles, which is conducive to enhancing light harvesting and increases the adsorption sites of water molecules, while the loading of LiCl increases the hydrophilicity and sorption capacity.

由于分级多孔结构、丰富的水吸附位点和LiCl晶体的优化，LiCl@PC-PPy比纯LiCl粉末具有更好的吸附动力学。此外，PC-PPy笼的大空腔可以用作储水器，以减少液体泄漏。光照下，PPy层将太阳能转化为热量并驱动蒸汽产生，以释放储存在PC-PPy笼的孔隙和腔内捕获的大气水。另一方面，LiCl@PC-PPy亲水性的改善有助于在三维骨架壳的大孔中形成凹形半月板，降低PC-PPy与水半月板之间的热阻；因此，通过亲水性增强效应，可以最大限度提高热-蒸发转化效率。

Owing to the hierarchical porous structures, the plentiful water adsorption sites, and the refinement of LiCl crystals, LiCl@PC-PPy exhibits much improved sorption kinetics than pure LiCl powders. Moreover, the big cavities of the PC-PPy cages can function as the water reservoir to reduce liquid leaks. When exposed to solar light, the roughness the PPy layer converts the solar energy into heat and drives steam generation to release the captured atmospheric water stored in the pores and the cavities of the PC-PPy cages. Moreover, the improved hydrophilicity of the LiCl@PC-PPy contributes to the formation of a concave meniscus in the macropores on the 3D skeleton shell, reducing the thermal resistance between the PC-PPy and the water meniscus; therefore, the heat flux for high thermal-to-evaporation conversion efficiency is maximized by the hydrophilicity-enhanced perimeter effect.

作为概念验证，所设计的简易AWH装置可以在夜间吸收水蒸汽1.55g/g,并在1天的室外运行中收集1.53 g/(g day)水，收集的水可以满足世界卫生组织和环境保护署定义的饮用水标准。利用现有的器件设计，LiCl@PC-PPy复合材料在解决离网、偏远山区和沙漠地区淡水短缺方面具有较大的应用潜力。相信这项工作可以为改善高容量复合吸附剂的吸附/脱附动力学和减少液体泄漏开辟一条新的途径。

As a proof-of-concept demonstration, the fabricated AWH device can absorb 1.55 g_water/g_sorbent at night and collect 1.53 g_water/g_sorbent of water in 1-day outdoor operation, and the collected water can meet the drinking water standards defined by the World Health Organization (WHO) and the Environmental Protection Agency (EPA). By drawing on the advanced device design of some current researchers, the LiCl@PC-PPy composite may have great application potential in solving the freshwater shortage for off-grid, remote mountainous and desert regions. It is believed that this work may open up a new pathway for improving the sorption/desorption kinetics and reducing the liquid leakage of high-capacity composite sorbents.

原文链接: https://pubs.acs.org/doi/10.1021/acsami.2c04845?ref=PDF