Date of Degree
MS (Master of Science)
First Committee Member
Second Committee Member
This thesis examines the effects of temperature on the electrochemistry of an aqueous solvent, HNO3, and a non aqueous solvent, acetonitrile and their respective analytes. It has been demonstrated previously that lowering the temperature of a solvent expands the available potential window in which to perform electrochemical experiments. The working window of an aqueous solvent is limited by the electrolysis of water. Cyclic voltammetry was utilized to examine the temperature effects on the rates of the oxidation and reduction of the solvent as well as the effects on the redox species in solution. The redox species experienced decreased peak splitting with lower temperatures, and the diffusion constants and rate constants were lowered as the temperature decreased. It was determined that the solvent window of the HNO3 solution was extended in experiments conducted at lower temperatures. The voltage window went from 2.349 V at 25 °C to 2.671 V at 5 °C. No significant improvement in the voltage window of acetonitrile was seen at lower temperatures. Rate constants for the oxidation and reduction of water were lowered and the voltage window of nitric acid expanded.
Electrochemical reactions are processes where the transfer of electrons is involved. Electrochemical reactions are part of many everyday items including batteries and fuel cells. Cyclic voltammetry is one technique that is used to analyze these systems. Cyclic voltammetry is carried out by applying a voltage to an electrode and measuring the current that is produced as the potential is scanned through a range of voltages. To carry out cyclic voltammetry, a solvent and electrolyte are needed. The span of the voltages able to be used is typically limited by the solvent in aqueous cases, where water is electrolyzed.
In this study, the effect of temperature on the solvent during cyclic voltammetry is examined. It is found that lowering the temperature of an aqueous solution extends the solvent window, and thus the range of potentials that can be utilized. This may be useful for analyzing compounds that are typically out of the available solvent window.
ix, 36 pages
Includes bibliographical references (page 36).
Copyright 2014 Emily Null
Null, Emily Mrugacz. "Temperature effects on the potential window of water and acetonitrile and heterogeneous electron transfer rates of outer sphere redox probes." MS (Master of Science) thesis, University of Iowa, 2014.