Department of Aerospace and Mechanical Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering of China, Sichuan University , Chengdu 610065, P. R. China.
ACS Nano. 2017 Jun 27;11(6):5510-5518. doi: 10.1021/acsnano.7b00367. Epub 2017 May 18.
The ability to efficiently utilize solar thermal energy to enable liquid-to-vapor phase transition has great technological implications for a wide variety of applications, such as water treatment and chemical fractionation. Here, we demonstrate that functionalizing graphene using hydrophilic groups can greatly enhance the solar thermal steam generation efficiency. Our results show that specially functionalized graphene can improve the overall solar-to-vapor efficiency from 38% to 48% at one sun conditions compared to chemically reduced graphene oxide. Our experiments show that such an improvement is a surface effect mainly attributed to the more hydrophilic feature of functionalized graphene, which influences the water meniscus profile at the vapor-liquid interface due to capillary effect. This will lead to thinner water films close to the three-phase contact line, where the water surface temperature is higher since the resistance of thinner water film is smaller, leading to more efficient evaporation. This strategy of functionalizing graphene to make it more hydrophilic can be potentially integrated with the existing macroscopic heat isolation strategies to further improve the overall solar-to-vapor conversion efficiency.
利用太阳能高效地实现液体到蒸汽的相变，这对于水处理和化学分离等各种应用具有重要的技术意义。在这里，我们证明了通过亲水性基团功能化石墨烯可以极大地提高太阳能蒸汽产生效率。我们的结果表明，与化学还原氧化石墨烯相比，经过特殊功能化的石墨烯可以将整体太阳能到蒸汽的效率从 38%提高到 48%，在单太阳条件下。我们的实验表明，这种改进是一种表面效应，主要归因于功能化石墨烯更亲水的特性，由于毛细作用，这会影响蒸汽-液体界面上水的弯月面轮廓。这将导致靠近三相接触线的水膜更薄，因为较薄的水膜的阻力较小，导致蒸发更有效率。这种使石墨烯更亲水的功能化策略可以与现有的宏观热隔离策略相结合，以进一步提高整体太阳能到蒸汽的转换效率。
