Unveiling surface redox charge storage of interacting two-dimensional heteronanosheets in hierarchical architectures.
Two-dimensional (2D) heteronanosheets are currently the focus of intense study due to the unique properties that emerge from the interplay between two low-dimensional nanomaterials with different properties. However, the properties and new phenomena based on the two 2D heteronanosheets interacting in a 3D hierarchical architecture have yet to be explored. Here, we unveil the surface redox charge storage mechanism of surface-exposed WS2 nanosheets assembled in a 3D hierarchical heterostructure using in situ synchrotron X-ray absorption and Raman spectroscopic methods. The surface dominating redox charge storage of WS2 is manifested in a highly reversible and ultrafast capacitive fashion due to the interaction of heteronanosheets and the 3D connectivity of the hierarchical structure. In contrast, compositionally identical 2D WS2 structures fail to provide a fast and high capacitance with different modes of lattice vibration. The distinctive surface capacitive behavior of 3D hierarchically structured heteronanosheets is associated with rapid proton accommodation into the in-plane W-S lattice (with the softening of the E2g bands), the reversible redox transition of the surface-exposed intralayers residing in the electrochemically active 1T phase of WS2 (with the reversible change in the interatomic distance and peak intensity of W-W bonds), and the change in the oxidation state during the proton insertion/deinsertion process. This proposed mechanism agrees with the dramatic improvement in the capacitive performance of the two heteronanosheets coupled in the hierarchical structure.
†Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1 Seochon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
Qasim
Q
Mahmood
‡Beamline Research Division, Pohang Accelerator Laboratory, Pohang, Republic of Korea.
Min Gyu
MG
Kim
§School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Republic of Korea.
Sol
S
Yun
∥Chemistry Department, Brookhaven National Laboratory, New York 11973, United States.
Seong-Min
SM
Bak
∥Chemistry Department, Brookhaven National Laboratory, New York 11973, United States.
Xiao-Qing
XQ
Yang
⊥Department of Energy Engineering, Department of Chemistry, and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology(UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
Hyeon Suk
HS
Shin
†Department of Chemical Engineering, College of Engineering, Kyung Hee University, 1 Seochon-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
Woo Sik
WS
Kim
△Department of Materials Science and Engineering Materials Research Laboratory and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
Paul V
PV
Braun
§School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Republic of Korea.
Ho Seok
HS
Park
2D nanomaterial; energy storage mechanism; heteronanosheet; hierarchical structure; in situ spectroscopy; redox reaction