Publication date: 10th April 2024
Adsorption and dissociation of water (hydration) on surfaces and resulting surface protonic conduction can expectedly enhance the performance of positrodes and corresponding proton ceramic steam electrolyzers and fuel cells. In p-type electron conducting oxide positrodes, a combination of hydration and oxidation (hydroxidation) may also be active on surfaces under oxidizing conditions, which requires further investigation. In this work we study nickel oxide (NiO), a p-type electron conducting oxide, as a model material to study surface protonic transport under humidified and oxidizing conditions. The area specific concentration of adsorbed water and surface protonic transport are measured and interpreted from thermogravimetry and macroscopic conductivity results, and both exhibit distinctive behaviours for different hydration stages at intermediate and ambient temperature (600-25 oC). The results help to understand the roles of hydration and hydroxidation in protonation and protonic transport on p-type electron conducting materials, including positrode perovskites that are part of our ongoing studies.
This work is supported by FME HYDROGENi which is financed by its industry partners and the Norwegian government through the Research Council of Norway’s Centres for Environment-friendly Energy Research programme (FMETEKN, project no. 333118)