The electrochemical, catalytic and electrocatalytic properties of Nonstoichiometric MnO2 depend upon their defect structure , the concentration of defects/unit area and the nature of cations present as dopants in their intersties.
MnO2 can exist in six types of polymorphs- hollandite( α -MnO2), pyrolusite(β MnO2), ramsdellite(γ-MnO2), romanechite(δ-MnO2),hexagonal( ε-MnO2) and todorokite.They are put to the specific uses. Of these MnO2 crystal stuctures, the one called γ- MnO2 having ramsdellite(JCPDF 82-2169) structure and containing Co(II) ions as dopants has been used in direct methanol fuel cell (DMFC) .
It can be prepared by electrodeposition using Pt anode in 0.2M/L HF containg 0.7M/L MnSO4. Co(II) ions acting as dopant can be introduced by the additon of 0.001-0.1M/L using a constant current density of 1-6 A dm^-2 at room temperature by using a steel plate( 1CH18N10) as cathode.The precipitated deposit was filtered off(Shotta filter paper) and dried in air at 80-90C for one hour.
The electrochemical, catalytic and electrocatalytic properties of Nonstoichiometric MnO2 depend upon their defect structure , the concentration of defects/unit area and the nature of cations present as dopants in their intersties.
MnO2 can exist in six types of polymorphs- hollandite( α -MnO2), pyrolusite(β MnO2), ramsdellite(γ-MnO2), romanechite(δ-MnO2),hexagonal( ε-MnO2) and todorokite.They are put to the specific uses. Of these MnO2 crystal stuctures, the one called γ- MnO2 having ramsdellite(JCPDF 82-2169) structure and containing Co(II) ions as dopants has been used in direct methanol fuel cell (DMFC) .
It can be prepared by electrodeposition using Pt anode in 0.2M/L HF containg 0.7M/L MnSO4. Co(II) ions acting as dopant can be introduced by the additon of 0.001-0.1M/L using a constant current density of 1-6 A dm^-2 at room temperature by using a steel plate( 1CH18N10) as cathode.The precipitated deposit was filtered off(Shotta filter paper) and dried in air at 80-90C for one hour.
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