Real-time synchrotron radiation photoelectron spectroscopic observation of high temperature thermal anneal processes of oxidized graphene

Hozumi, Hideaki*; Yamaguchi, Hisato*; Kaga, Toshihide*; Eda, Goki*; Mattevi, C.*; Ogawa, Shuichi*; Yoshigoe, Akitaka ; Ishizuka, Shinji*; Teraoka, Yuden; Yamada, Takatoshi*; Takakuwa, Yuji*; Chhowalla, M.*

In order to clarify the time evolution of the chemical bonding state during thermal reduction of graphene oxide (GO), real-time photoelectron spectroscopy was employed for observing the thermal reduction kinetics of GO. The GO was prepared by the modified Hummer method. The experiments were performed using the surface reaction analysis apparatus placed at the BL23SU of SPring-8. The XPS measurements were performed simultaneously during the annealing at 473 K, 673 K, 873 K, and 1073 K. The C1s photoelectron spectra are decomposed by 8 components. The - transition loss peak intensity is propotional to the intensity of sp graphene components with temperature elevation. In addition, defect intensity increased in proportion with the sp graphene intensity. These facts indicate that defects were formed on the graphene during reduction and these defects cause the recovery of electric conductivity, that is, the appearance of Fermi edge.