Wettability of graphene and interfacial water structure

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.

Automated summary

The study utilized vibrational sum-frequency-generation spectroscopy to elucidate the water structure at a water-graphene interface. The observation of an excellent correlation between water adhesion energy of graphene and the fraction of dangling OH groups suggests that VSFG can be an incisive technique for measuring water's adhesion energy on spatially confined interfaces. The results are anticipated to aid in understanding the wettability of low-dimensional materials.