| Abstract
| - A series of alkali nitrate/Pd composites were investigated for their thermal and chemical stability to separate hydrogen using a combination of thermogravimetric and analytical techniques. Alkali nitrates are promising proton conductors which normally do not start to decompose in a reducing environment until temperatures >600 °C have been attained. However, in the presence of Pd, the alkali nitrates undergo decomposition at significantly lower temperatures with decomposition starting at ∼80 °C for NaNO3, 130 °C for KNO3, and between 150 and 200 °C for RbNO3 and CsNO3. The overall decomposition process for the alkali nitrates occurs by reaction with hydrogen, catalyzed by the presence of Pd, which aids the dissociation of H2 → 2H+ + 2e. Decomposition occurs though a series of reactions that reduce the alkali nitrate to NH3, NO2, NO, and alkali metal or alkali metal oxides. In a moist, ambient atmosphere, the alkali metal products (M, M2O) readily convert to their respective metal carbonates. This work demonstrates that screening of promising oxo salts for hydrogen separation membranes by thermogravimetric analysis of the metals in the presence of Pd, the most commonly utilized catalytic layer, is a useful means of assessing their potential stability in hydrogen separation.
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