Electrochemical activation enabling structure reconstruction of Fe-doped MnO2 for enhancing pseudocapacitive storage

Authors：Liu, Shaobo; Huang, Hao; Yang, Chenggang; Liu, Yufei; Li, Hongjian; Xia, Hui; Qin, Ting; Zhou, Jianfei; Liu, Xiaoliang^*

Source：Chemical Engineering Journal, 2022, 441: 135967.

DOI：10.1016/j.cej.2022.135967

• Reconstruction
• Nanosheets and nanowires
• Oxygen defects
• High capacitance
• Pseudocapacitor

Monitoring and understanding of materials reconstructed under working conditions are vital to accurately identify active sites, clarify reaction mechanism and reasonably design advanced electrodes. Here, a Fe doped MnO2 (Fe-MnO2) nanosheet with unique features is demonstrated, unfolding dynamic reconstruction on both morphology and defect structures toward self-optimized pseudocapacitive storage, which can be easily controlled by galvanostatic charge/discharge activation. The results show that the Fe-MnO2 after activation is reconstructed from nanosheets to a composite structure of Fe-doped and oxygen-deficient nanosheets and nanowires. This composite structure endows the reconstructed Fe-MnO2 with accelerated electron and ion transfers and high electrochemical active surface area. Density functional theory (DFT) calculation and finite element simulation reveal that the co-existence of Fe doping and oxygen defects arouses more delocalized charges, and the nanowires on nanosheets display tip-enhanced electric field effects for attracting more ions, which effectively improves electron and ion transfer kinetics. The reconstructed Fe-MnO2 delivers a specific capacitance of 500.1 F g(-1) at 1 A g(-1), a significant self-optimized energy storage compared with Fe-MnO2 with 379.2 F g(-1). These observations demonstrate active morphology and crystallinity for outstanding pseudocapacitive storage of the Fe doped MnO2 electrode, offering a guidance to design the electrode materials with superior performance.

• Institution
  桂林理工大学