Understanding the wettability of graphene is important for various applications, such as water desalination, energy storage, and catalysis. However, the detailed water hydrogen-bonding structure at the water-graphene interface is not yet fully understood. Using vibrational sum-frequency-generation (VSFG) spectroscopy, we elucidate the water structure at a water-graphene interface. As the number of graphene layers increases, water molecules with dangling OH groups become more populated, indicating the transition from transparency to translucency. We compare the water contact angles on the graphene surfaces with VSFG results, showing an excellent correlation between the water adhesion energy of graphene and the fraction of dangling OH groups estimated from the VSFG spectrum. This observation suggests that the VSFG could be an incisive technique for measuring water's adhesion energy on any spatially confined interface where the water contact angle cannot be measured. We anticipate that the VSFG results will help to elucidate the wettability of low-dimensional materials.
Bibliographical noteFunding Information:
This work was supported by IBS-R023-D1 (M.C.) and a National Research Foundation of Korea grant funded by the Korean government ( NRF-2020R1A2C2010675 ) (K.K.). B.K.M. acknowledges financial support from the Korea Institute of Science and Technology Institutional Program.
© 2021 Elsevier Inc.
- SDG6: Clean water and sanitation
- SDG7: Affordable and clean energy
- SDG9: Industry, innovation, and infrastructure
- interfacial water structure
- measurement of water contact angle
- vibrational sum-frequency-generation spectroscopy
- wettability of graphene
ASJC Scopus subject areas
- Environmental Chemistry
- Chemical Engineering(all)
- Biochemistry, medical
- Materials Chemistry