Evaluation of temperature and electrolyte concentration dependent Oxygen solubility and diffusivity in phosphoric acid
| Autor: | Matthias Arenz, Michael Fleige, Kaspar Holst-Olesen, Gustav K. H. Wiberg |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
General Chemical Engineering
Diffusion Inorganic chemistry Proton exchange membrane fuel cell chemistry.chemical_element 02 engineering and technology Electrolyte Atmospheric temperature range 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Oxygen 0104 chemical sciences Catalysis chemistry.chemical_compound chemistry Electrochemistry Solubility 0210 nano-technology Phosphoric acid |
| Zdroj: | Electrochimica Acta. 209:399-406 |
| ISSN: | 0013-4686 |
| DOI: | 10.1016/j.electacta.2016.05.048 |
| Popis: | Reactant diffusion and solubility is of utmost important for providing sufficient reactant concentrations at a catalytic active surface. In high temperature proton exchange membrane fuel cells (HT-PEMFCs) the electrolyte consists of concentrated phosphoric acid embedded into a polybenzimidazole (PBI) membrane. Despite the elevated operation temperature of 150 °C, the observed oxygen reduction reaction (ORR) rates in HT-PEMFCs are significantly lower than in low temperature PEMFCs. Reduced reactant transport in combination with site blocking is often mentioned as possible inhibition factors. As a step towards studying the ORR under realistic conditions in half-cell setups, in the present study we investigate the oxygen solubility and diffusivity in diluted phosphoric acid electrolyte in a temperature range of 5 to 80 °C. The presented work demonstrates and discusses under which conditions reliable data for these constants can be obtained. In particular it is shown that the product of oxygen solubility and diffusivity, which determines the oxygen mass transport, first increases as function of temperature, but then decreases again above 60 °C. It seems that the decrease in oxygen solubility at higher temperatures is correlated to an increase in the apparent ORR activation energy. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect