Microtube‐Membrane Methodology for Electrochemical Synthesis and Study of Electroactive and Ionically Conductive Materials, and the Conductivity of MnO 2

A membrane‐based methodology for electrochemical synthesis and study of electroactive and ionically conductive materials is described. The Li + ‐intercalation material MnO 2 was used to demonstrate this methodology. The membrane was a polymeric support containing monodisperse gold microtubes (diameter 600 nm) that span the thickness of the membrane. Bipolar electrochemical synthesis of MnO 2 , from Mn 2+ solutions, was conducted across this membrane, resulting in deposition of monodisperse, hemispherical MnO 2 particles at the open ends of the tubes on one face of the membrane. The resulting microtube/MnO 2 composite membrane makes a convenient construct for investigating the transport properties of the MnO 2 particles. This was accomplished by mounting the membrane in a U‐tube cell, placing electrolyte solutions on either side, and driving an ionic current through the membrane. The ionic conductivity of MnO 2 was measured in this way, and found to be 40±10 μS cm −1 when LiCl or LiClO 4 solutions were used as the electrolyte. The mechanism of ionic conductivity through these MnO 2 particles is discussed.