Surface reactions on palladium hydride in vacuum, air and water studied in situ with mass spectrometry

The release of hydrogen from palladium hydride was studied in different environments, vacuum, open air with ∼ 40% relative humidity, air with varying relative humidity contained in a virtually closed volume, and from a sample immersed in liquid water. The release was followed in situ using mass spectrometry in vacuum and in the limited volume, and by measuring the weight change of the sample in open air. Based on the experimental results we conclude that in addition to the release in the form of molecular hydrogen, the main route in air and liquid water in contact with air, is reaction with oxygen. Further it was found that water catalyzed the reaction between hydrogen and oxygen and thereby increased the release rate of hydrogen by a factor > 100.