Effect of temperature on the γ-MnO2/“Ag2O” hydrogen getter structure

Abstract Manganese oxides based materials, as γ-MnO 2 /“Ag 2 O”, are considered to control the hydrogen risk from radioactive waste packaging. The efficiency of hydrogen trapping at room temperature has been demonstrated. However, in accidental conditions, the increasing temperature can be detrimental for hydrogen performance in nuclear waste packages. As a function of temperature, structural evolution of γ-MnO 2 /“Ag 2 O” getter was determined by X-Ray Diffraction (XRD), Pair Distribution Function (PDF) and Thermogravimetric Analysis (TGA). Kinetics of the hydrogen trapping were related to the structure evolution of γ-MnO 2 /“Ag 2 O”. Ramsdellite (R-MnO 2 ) and pyrolusite (β-MnO 2 ) were the main phases existing below 400 °C, then Ag-hollandite (quadratic), Ag-hollandite (monoclinic), Mn 2 O 3 and Mn 3 O 4 were formed at 500 °C, 600 °C, 700 °C and 850 °C, respectively. Hydrogen trapping was efficient until 400 °C where the γ-MnO 2 structure remains.