東北大学
統合化学国際共同大学院

Graphene serves as an ideal platform to investigate the microscopic structure and reaction kinetics at the graphitic electrode interfaces. However, graphene is susceptible to various extrinsic factors, e.g. substrate, causing much confusion and controversy. Hereby we have obtained cm-sized substrate-free monolayer graphene suspended on an electrolyte surface with gate tunability. Using sum-frequency spectroscopy, we have observed the structural evolution versus the gate voltage at the graphene/water interface. The Stern layer structure is invariant within the water electrolysis window, but undergoes a drastic change when switching on the electrochemical reactions. The electrode is turned from hydrophobic to hydrophilic near the onset of the hydrogen evolution reaction due to hydrogen adsorption.  The large-size suspended pristine graphene offers a new platform to unravel the microscopic processes at the graphitic electrode interfaces.