Electrodeposition of exfoliated nanosheet colloid from the partially substituted birnessite and electrochemical property

Partially substituted birnessite with Fe, Co, Ni and Cu for Mn was exfoliated to form nanosheet colloid and then their electrochemical properties were examined. The partially substituted birnessite can be exfoliated by tetrabutylammonium hydroxide acetonitrile solution. The electrodeposited films was grown from the exfoliated acetonitrile solution. The electrochemical capacitance of the films once increased at low substitution ratio and decreased with increase of the ratio. Within 10 atom% of the substitution ratio, the electrochemical capacitances are larger than that of non-substituted sample. Such increase seems to be related with DOS calculated by DV-Xα. From calculated DOS curves, the band of 3d orbital of Mn4+ tends to broaden at low substitution ratio and be restored with further increase of the substituent. The broadening results from increase of another Mn4+ circumstance, Mn4+O6 octahedron surrounded by both Mn3+ and substituent cation.

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► Partially substituted birnessite can be exfoliated in acetonitrile solution.
► Color of the nanosheet colloid solution slightly changes depending on the substituent.
► On substituting within 10 atom%, the electrochemical activity increased.
► The electrochemical property showed good agreement with electronic state simulated by DV-Xα.