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Experimental and Theoretical Investigation of the Effect of Oxygen Vacancies on the Electronic Structure and Pseudocapacitance of MnO 2
Author(s) -
Yan Lijin,
Shen Cheng,
Niu Lengyuan,
Liu Maocheng,
Lin Jianhua,
Chen Taiqiang,
Gong Yinyan,
Li Can,
Liu Xinjuan,
Xu Shiqing
Publication year - 2019
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201901015
Subject(s) - pseudocapacitance , raman spectroscopy , redox , oxygen , materials science , density functional theory , electronic structure , oxidation process , reactivity (psychology) , chemistry , capacitance , chemical engineering , inorganic chemistry , computational chemistry , supercapacitor , organic chemistry , medicine , physics , alternative medicine , electrode , pathology , optics , engineering
Defect engineering is an effective way to modulate the intrinsic physicochemical properties of materials. In this work, δ‐MnO 2 with oxygen vacancies is fabricated by a simple oxidation or reduction process, and the relationship between the electronic structure and pseudocapacitance is systematically studied through experimental analysis and theoretical calculations. The peaks in the Raman spectra of the as‐prepared samples are shifted compared with those of pure MnO 2 and the Mn 3+ /Mn 4+ ratio and O species content also change after the introduction of oxygen vacancies. The optimized samples exhibit a better specific capacitance of 207 F g −1 after the oxidation process and 181.4 F g −1 after the reduction treatment compared with only 143.9 F g −1 for the pure MnO 2 . The samples obtained through the oxidation or reduction process also retain 93.3 or 86.4 % of the initial capacity after 5000 cycles. The excellent properties are attributed to the enhanced conductivity and increased surface reactivity or electrochemically active sites. Theoretical calculations demonstrate that the presence of oxygen vacancies leads to an increase in the density of states, which improves the redox reaction of MnO 2 . This study will provide a reference for exploring and designing highperformance pseudocapacitive materials.