4. phase change reaction for enhancing the seebeck coefficient of electrochemical thermocell
Name: Hongyao Zhou
Grad Year: 2021
Waste heat is a ubiquitous source of energy. Technologically, recovery of low grade heat below 100 ℃ is especially important due to lack of viable method such as steam engines. Electrochemical thermocell converts heat directly to electric power. It consists of two electrodes where the same redox reaction occurs, and the temperature difference between the electrodes causes potential difference and thus generates voltage. Seebeck coefficient, which denotes the generated voltage per temperature difference is the determining parameter of the thermal efficiency, and the value is governed by the entropy change during the redox reaction. In this presentation, we propose a thermocell using acetone and iso-propanol as the redox couple and demonstrates the vaporization entropy of acetone above the boiling point increases the Seebeck coefficient. Moreover, the vaporization and subsequent condensation of acetone creates the concentration difference between the hot-side and cold-side cells and also increases the Seebeck coefficient according to Nernst equation. Reversible and stable redox reaction of acetone and iso-propanol is enabled by Neutral pH solution and Sn-modified Pt catalyst. Utilization of volatile redox specie provides a new strategy of enhancing the performance of thermocells.
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