Changes in kinetic parameters of decomposition of MgH2 destabilized by irradiation with C2+ ions

• Introducing defects using C2+ ions improves MgH2 hydrogen sorption kinetics.
• Irradiation shifts β-MgH2 peaks to higher angles and decreases crystallite size.
• Saturation of defects is achieved in the sample irradiated with the lowest fluence.
• The ratio of three differently bonded hydrogen atoms changes upon irradiation.
• There is change in the hydrogen desorption mechanism in irradiated samples.

In attempt to improve desorption behaviour of MgH2, the influence of well-defined structural changes induced within a thin surface layer of MgH2 have been investigated. The defects were induced by 30 keV C2+ ions irradiation using different fluencies ranging from 1012–1016 ions/cm2. The hydrogen desorption properties were investigated by thermal desorption spectroscopy analysis (TDS), while kinetics parameters were deduced using non-isothermal kinetic approach. The existence of multiple TDS peaks and different curve shapes indicate difference in desorption mechanism. To understand changes in the rate limiting step, shapes of all desorption peaks have been analyzed using different kinetic models. Regarding the irradiated sample, the function based on Avrami–Erofeev model with n=4n=4 gives the best fit over θ   range from 0.3 to 0.8 while for untreated sample the best fit is obtained for Avrami–Erofeev model with n=3n=3. The change in mechanism can be attributed to the different way of nuclei growth.