Structure evolution of graphene oxide during thermally driven phase transformation: is the oxygen content really preserved?
A mild annealing procedure was recently proposed for the scalable enhancement of graphene oxide (GO) properties with the oxygen content preserved, which was demonstrated to be attributed to the thermally driven phase separation. In this work, the structure evolution of GO with mild annealing is closely investigated. It reveals that in addition to phase separation, the transformation of oxygen functionalities also occurs, which leads to the slight reduction of GO membranes and furthers the enhancement of GO properties. These results are further supported by the density functional theory based calculations. The results also show that the amount of chemically bonded oxygen atoms on graphene decreases gradually and we propose that the strongly physisorbed oxygen species constrained in the holes and vacancies on GO lattice might be responsible for the preserved oxygen content during the mild annealing procedure. The present experimental results and calculations indicate that both the diffusion and transformation of oxygen functional groups might play important roles in the scalable enhancement of GO properties.
School of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Materials Processing Technology of MOE, Tsinghua University, Beijing, P. R. China.
Pengzhan
P
Sun
Center for Nano and Micro Mechanics, Tsinghua University, Beijing, P. R. China; Department of Engineering Mechanics, Tsinghua University, Beijing, P. R. China.
Yanlei
Y
Wang
Department of Mechanical Engineering, Tsinghua University, Beijing, P. R. China.
He
H
Liu
School of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Materials Processing Technology of MOE, Tsinghua University, Beijing, P. R. China.
Kunlin
K
Wang
Department of Mechanical Engineering, Tsinghua University, Beijing, P. R. China.
Dehai
D
Wu
Center for Nano and Micro Mechanics, Tsinghua University, Beijing, P. R. China; Department of Engineering Mechanics, Tsinghua University, Beijing, P. R. China.
Zhiping
Z
Xu
School of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Materials Processing Technology of MOE, Tsinghua University, Beijing, P. R. China; Center for Nano and Micro Mechanics, Tsinghua University, Beijing, P. R. China.
Hongwei
H
Zhu
D006108:Graphite / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D044367:Phase Transition
D010087:Oxides; D006108:Graphite; D010100:Oxygen