Electrochemical Response of Nanocrystalline Tetragonal Manganese Dioxides Prepared by Spray Vapor Pyrolysis and Ball Milling
详细信息 查看全文
- 作者：Christiane Poinsignon ; Holger Klein ; Pierre Strobel ; Claude Roux ; Christine Surcin
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：July 12, 2007
- 年：2007
- 卷：111
- 期：27
- 页码：9644 - 9651
- 全文大小：544K
- 年卷期：v.111,no.27(July 12, 2007)
- ISSN：1932-7455
文摘
The electrochemical and microstructural properties of nanometric tetragonal 
-MnO2 (MD) prepared by high-energy ball milling (BM) and spray pyrolysis (nano-) were studied in comparison with the original volumetricphase (micro-). The microstructure was characterized by X-ray diffraction and transmission electronmicroscopy. Electrochemical properties were studied by step linear voltametry in 1 M KOH. Both theequilibrium potential and the incremental capacity at high potential of the MnO2 electrode increase when thecrystallite size decreases. Ball-milled MD and nano- both become insertion materials but only the laterpresents a good cyclability. The increase in electrode potential in 1 M KOH measures the decrease in Gibbsfree energy due to the surface energy contribution (1.3 J/m2) generated by the nanometric size of the particlesat the solid-liquid interface. Thermogravimetric analysis measurements in the 300-1200 
C range show forall samples a decrease in MnO2-Mn2O3 transition temperature which also leads to a calculation of the surfaceenergy of nanometric samples, according to the Gibbs-Thomson relationship. At the solid-gas interface,nano- has a surface energy 
three times larger than BM samples: 0.6 J/m2 for BM samples and 1.9 J/m2for nano- ones. That illustrates the main differences between both synthesis processes: crystal growth underequilibrium for nano-, size decrease by striking, and lamination leading to unstable nanometric BM samples.
-MnO2 (MD) prepared by high-energy ball milling (BM) and spray pyrolysis (nano-) were studied in comparison with the original volumetricphase (micro-). The microstructure was characterized by X-ray diffraction and transmission electronmicroscopy. Electrochemical properties were studied by step linear voltametry in 1 M KOH. Both theequilibrium potential and the incremental capacity at high potential of the MnO2 electrode increase when thecrystallite size decreases. Ball-milled MD and nano- both become insertion materials but only the laterpresents a good cyclability. The increase in electrode potential in 1 M KOH measures the decrease in Gibbsfree energy due to the surface energy contribution (1.3 J/m2) generated by the nanometric size of the particlesat the solid-liquid interface. Thermogravimetric analysis measurements in the 300-1200 C range show forall samples a decrease in MnO2-Mn2O3 transition temperature which also leads to a calculation of the surfaceenergy of nanometric samples, according to the Gibbs-Thomson relationship. At the solid-gas interface,nano- has a surface energy three times larger than BM samples: 0.6 J/m2 for BM samples and 1.9 J/m2for nano- ones. That illustrates the main differences between both synthesis processes: crystal growth underequilibrium for nano-, size decrease by striking, and lamination leading to unstable nanometric BM samples.