Microtube‐Membrane Methodology for Electrochemical Synthesis and Study of Electroactive and Ionically Conductive Materials, and the Conductivity of MnO₂

Abstract

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 À 1 when LiCl or LiClO 4 solutions were used as the electrolyte. The mechanism of ionic conductivity through these MnO 2 particles is discussed.[a] J. Figure 1. a) A gold-microtube membrane, and b) bipolar synthesis/deposition of MnO 2 across such a membrane. Dimensions are not to scale.

The state of understanding of the electrochemical behaviours of a valve-regulated lead–acid battery comprising manganese dioxide-impregnated gel polymer electrolyte

“…This allows the ions to move more easily through the electrolyte, resulting in higher ionic conductivity. 34 Furthermore, a decreasing trend of ionic conductivity is observed in the 5 wt% MnO 2 and 7 wt% MnO 2 @PVA gel systems. As the viscosity of a solution increases, the ions have a harder time moving around, which decreases the ionic conductivity.…”

Imaging Cycle-Induced Damage of MnO2 Microparticles

“…1). [21][22][23][24][25] A recent review describes such membranes in detail. 25 The polymeric host membrane contained monodisperse 800 nm diameter pores, making the outside diameter of the gold microtubes 800 nm.…”

“…Preparation of the gold-microtube membranes.-The method used to prepare the gold-microtube membranes has been described in detail previously. [21][22][23][24][25] Briefly, ion-tracked polyethylene terephthalate (PET) membranes (12 μm thick) were obtained from GSI (Darmstadt, Germany). Chemical etching 26,27 was used to prepare 800 nm diameter pores in these membranes.…”

“…1a) to make electrical contact to the gold microtubes within the pores. 28,29 The other gold surface film was removed by scrubbing the surface with a cotton swab wetted with ethanol 21,28 to expose the ends of the gold microtubes where the MnO 2 particles were deposited (Fig. 1a).…”

“…[30][31][32] Aqueous solutions 50 mM in manganese acetate and 0.1 M in sodium sulfate were used here. 21,33,34 The gold-microtube membrane was mounted in a U-tube cell 25,35 with this manganese solution in the half-cell facing the open gold microtubes (up in Fig. 1a).…”