Ma Xiaolong, Jia Xiaodong, Gao Hui, Wen Dongsheng
School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K.
School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, P. R. China.
ACS Appl Mater Interfaces. 2021 Dec 8;13(48):57153-57162. doi: 10.1021/acsami.1c17249. Epub 2021 Nov 26.
Solar vapor generation (SVG) typically uses a solar absorbing material at the water-air interface to convert solar energy into heat for evaporation. However, the intrinsic solar absorption of the material determines the upper limit of the solar energy capture. By designing a light-trapping surface structure with open pores and channels, we can break this limit and further improve the absorption by enabling multiple reflections within the surface. Polypyrrole (PPy) is emerging as a promising solar thermal material. In this work, we propose an ultrasonic spray coating method to obtain a nanofiber light-trapping coating by copolymerization with dopamine (DA), which can be directly synthesized at room temperature rapidly (30 min). Due to its excellent wettability, this coating can transport water and can be directly coated on the thermal insulating layer, not requiring an additional water transport layer. This nanoscale coating significantly improves solar absorption at different incident angles across the full solar spectrum, achieving the highest solar-to-thermal conversion efficiency of 95.8% at 1.385 kg·m·h under 1 sun. When applied on salt water, this solar evaporator achieves self-cleaning in the absence of solar irradiation. Moreover, the surface structure can be further tuned into granular/plane-fibrous/plane-granular structures by using different oxidants or surfactants, and their formation mechanisms are also proposed. This PPy-DA nanofiber coating shows great potential for SVG and other applications based on a PPy material, especially for those requiring a certain surface morphology.
太阳能蒸汽发生（SVG）通常在水 - 空气界面使用太阳能吸收材料，将太阳能转化为热量以进行蒸发。然而，材料的固有太阳能吸收决定了太阳能捕获的上限。通过设计具有开孔和通道的光捕获表面结构，我们可以突破这一限制，并通过在表面内实现多次反射来进一步提高吸收率。聚吡咯（PPy）正成为一种有前途的太阳能热材料。在这项工作中，我们提出了一种超声喷雾涂层方法，通过与多巴胺（DA）共聚来获得纳米纤维光捕获涂层，该涂层可在室温下快速（30分钟）直接合成。由于其优异的润湿性，这种涂层可以传输水，并且可以直接涂覆在隔热层上，无需额外的水传输层。这种纳米级涂层在整个太阳光谱的不同入射角下显著提高了太阳能吸收，在1个太阳辐射强度下，当蒸发速率为1.385 kg·m·h时，实现了95.8%的最高太阳能 - 热转换效率。当应用于盐水时，这种太阳能蒸发器在无太阳辐射的情况下实现自清洁。此外，通过使用不同的氧化剂或表面活性剂，表面结构可以进一步调整为颗粒状/平面纤维状/平面颗粒状结构，并提出了它们的形成机制。这种PPy - DA纳米纤维涂层在SVG以及基于PPy材料的其他应用中显示出巨大潜力，特别是对于那些需要特定表面形态的应用。
