Single-layer graphene prevents Cassie-wetting failure of structured hydrophobic surface for efficient condensation

Junxian Pei; Yutian Liao; Qian Li; Kui Shi; Jia Fu; Xuejiao Hu; Zhi Huang; Longjian Xue; Xu Xiao; Kang Liu

doi:10.1016/j.jcis.2022.01.157

Single-layer graphene prevents Cassie-wetting failure of structured hydrophobic surface for efficient condensation

J Colloid Interface Sci. 2022 Jun:615:302-308. doi: 10.1016/j.jcis.2022.01.157. Epub 2022 Jan 29.

Authors

Junxian Pei¹, Yutian Liao², Qian Li², Kui Shi², Jia Fu², Xuejiao Hu², Zhi Huang³, Longjian Xue⁴, Xu Xiao⁵, Kang Liu⁶

Affiliations

¹ MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China; State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, Chengdu 610065, China.
² MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China.
³ MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China. Electronic address: zhihuang@whu.edu.cn.
⁴ MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China. Electronic address: xuelongjian@whu.edu.cn.
⁵ Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang 313001, China; School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China.
⁶ MOE Key Laboratory of Hydraulic Machinery Transients, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China. Electronic address: kang.liu@whu.edu.cn.

PMID: 35149348
DOI: 10.1016/j.jcis.2022.01.157

Abstract

Hypothesis: Structured hydrophobic surfaces often suffer from Cassie-wetting failure due to trapped water in structure gaps for a long-term operation. Sustainable Cassie-wetting on such surface could be achieved by coating an atom-thick and moisture-impermeable graphene on it.

Experiments: Water contact angles were measured to clarify the effect of graphene on wetting, and water impermeability was verified by moisture deposition and evaporation. Sliding angle measurements and vapor condensation were carried out to demonstrate the stable Cassie-state wetting and application.

Findings: Interestingly we found the graphene does not significantly disrupt the wetting behavior of the structured hydrophobic surface, showing a wettability transparency. Moreover, the impermeability of graphene keeps moisture away from the structure gaps. Owning to the combination of these two properties, droplets on the graphene-coated structured surface exhibit a stable Cassie-state hydrophobic wetting, even under the situation of moisture deposition and evaporation. Using the modified surface, we also found a 40-100% increase in condensation efficiency for a 5-hour vapor condensation at a subcooling of 40 °C. These results suggest an effective strategy to prevent Cassie-wetting failure of structured hydrophobic surface and are expected to promote its further application in more complex conditions.

Keywords: Cassie-wetting failure; Condensation; Single-layer graphene; Structured hydrophobic surface; Wetting.