EASTERN NAZARENE COLLEGE

MANY DIFFERENCES, ONE FAITH

   Research, Dr. Wooster   

High Temperature Electrochemistry in the Solid State

            Microelectrodes have opened the door to exploring voltammetry in rigid and semi-rigid solvents to study the solid solution electrochemistry of ionic or non-ionic molecular or metal complex electron donors and acceptors. Recent investigations of poly(ether)s containing dissolved alkali metal salts (polymer electrolytes) as rigid or semi-rigid media reveal that, while solid-state and fluid electrolyte solution voltammetry is conceptually similar, there are important differences in execution of solid-state experiments as compared to fluid solution experiments. 

            Some features of solid-state voltammetry that arise from the slow transport rates typical of solids and semi-solids are: (i) Ionic conductivities of the polymer electrolytes are typically meager, favoring use of microelectrodes and the associated small currents, to avoid iR_uncomp effects. (ii)  Electroactive solutes, like the electrolyte ions, diffuse slowly in polymer electrolyte solvents, with highly variable rates that change with temperature, polymer phase-state (partly crystalline, amorphous), redox solute and electrolyte concentration, and sorption of vapors of plasticizing organic monomers.  There are likewise important physical and chemical consequences of using rigid electrochemical solutions:  (i) Since the polymer solvents are not volatile, they can be used as thin films. This allows useful chemical manipulations via the gas/polymer contact, such as adding or removing volatile reagents and designing new kinds of gas sensors.  (ii) Heterogeneous electron transfer rates may be slowed at the polymer/electrode interface, so that measurements of solid-state electron transfer dynamics are possible in spite of the iR_uncomp and slow diffusion aspects of polymer solutions.

            My objective is to take advantage of the unique properties of polymer electrolytes in the development of new electrochemical techniques employed at elevated temperatures. The ability to attain temperatures in excess of 200^oC with these solid-state systems opens a new window to experimental promise.  Initial efforts will be directed at developing the technical capabilities necessary for performing these experiments and applying these techniques to the study of electrochemical systems that are currently well defined and understood at room temperature. Future experiments would examine: (i) The benefit of increased solubility at high temperature. A likely candidate in these studies would be the use of metallophorphryns (limited solubility at room temperature) in the electrocatalytic reduction of dioxygen, (ii) The thermal activation of electron transfer reactions, (iii) Introduction of ligands from the gas phase in the study of ligand substitution reactions.

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