Soft X-ray absorption spectroscopic investigation of MnO2/graphene nanocomposites used in supercapacitor

Han Wei Chang, Yu Cheng Huang, Jeng Lung Chen, Chi Liang Chen, Jin Ming Chen, Da Hua Wei, Wu Ching Chou, Chung Li Dong*, Yu Chen Tsai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Electrochemistry and X-ray absorption spectroscopy (XAS) of MnO2/reduced graphene oxide (RGO) were made to evaluate capacitive performance and electronic structure as a supercapacitor. MnO2 was deposited on the surface of RGO by a spontaneous redox reaction. At low current density (1 A g−1), the specific capacitance of MnO2/RGO (MRGO) greatly increased with increasing growth time from 281 to 462 F g−1. Electrochemical results show that the specific capacitance of RGO and MRGO arises from the combined contributions of electrochemical double-layer capacitance (EDLC) and pseudo-capacitance. To gain insights into the charge storage mechanism of RGO and MRGO, it was characterized using ex-situ soft XAS techniques at Mn L-edge and C, O K-edges in the charging/discharging process. The ex-situ soft XAS results provide evidence that the contribution of RGO to specific capacitance involves an oxygen-functionality-related contribution of pseudocapacitance and EDLC. In addition, the specific capacitance of MRGO reveals pseudocapacitive contributions from the redox processes that involve the Mn(III)/Mn(IV) redox reaction in MnO2. This work utilizes electrochemical and ex-situ XAS techniques to elucidate charge storage mechanism for supercapacitor applications.

Original languageEnglish
JournalCatalysis Today
DOIs
StateAccepted/In press - 2021

Keywords

  • MnO
  • Supercapacitor
  • X-ray absorption spectroscopy

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