Effect of surface oxidation on the solution of hydrogen in vanadium

Abstract

The formation of vanadium surface oxides and their influence on the absorption of hydrogen were studied by XPS and TDMS methods. Vanadium hereby serves as a model system for hydrogen metal interaction. Different stable and unstable oxides indicated by the oxidation number of vanadium have been investigated: oxidation number +5 corresponding to stable V₂O₅; oxidation number +3 corresponding to stable V₂O₃ and lower than +3, corresponding to unstable oxides. Exposure of a cleaned V sample to different oxygen dosages (1 L – 1000 L, p_O2 = 1 × 10^–4 Pa) at room temperature leads to the formation of unstable oxides with oxidation numbers smaller than 3. V-O bondings break up at temperatures higher than 290 °C and oxygen desorbs. Besides the dosage the oxide formation is also influenced by the temperature. All these oxides act as surface barriers and prevent the absorption of hydrogen by vanadium.