Modeling hydrolysis kinetics of dual phase α-Mg/LPSO alloys

This work proposes a new modeling of hydrolysis reaction in simulated seawater solution (35 g/L NaCl) with alloys containing α-Mg and Long Period Stacking Ordered (LPSO) phases. Alloys with different chemical compositions or thermal treatments were synthesized, leading to different (i) microstructures, (ii) α-Mg over LPSO phase fractions or (iii) LPSO type (18R or 14H). Classical nucleation and growth equation is used as an indicator of the reaction mechanisms but a new model is proposed to describe the complex kinetics curves (Vol (H2) = f(t)) obtained. This new model has several advantages: (i) it allows to discriminate the contribution of each phase, (ii) it could be applied to any alloy with phases reacting and (iii) it applies to the whole kinetics curves (i.e. from 0 to 100% yield). It is supported by the comparisons between the different alloys and SEM observations of their microstructure before and after exposure to the seawater solution

Autonomous hydrogen production for proton exchange membrane fuel cells PEMFC

This paper focuses on hydrogen production for green mobility applications (other applications are currently under investigation). Firstly, a brief state of the art of hydrogen generation by hydrolysis with magnesium is shown. The hydrolysis performance of Magnesium powder ball–milled along with different additives (graphite and transition metals TM = Ni, Fe, and Al) is taken for comparison. The best performance was observed with Mg–10 wt.% g mixtures (95% of theoretical hydrogen generation yield in about 3 min). An efficient solution to control this hydrolysis reaction is proposed to produce hydrogen on demand and to feed a PEM fuel cell. Tests on a bench fitted with a 100 W Proton Exchange Membrane (PEM) fuel cell have demonstrated the technological potential of this solution for electric assistance applications in the field of light mobility

Hydrogen generation by hydrolysis reaction using magnesium alloys with long period stacking ordered structure

n the present work are reported the hydrogen generation performances of Long Period Stacking Ordered (LPSO) compounds with 18R, 14H and 10H-type structures by hydrolysis reaction in simulated seawater solution (35 g/L NaCl). LPSO compounds and LPSO + Mg alloys synthesized by induction melting are described in the light of their microstructural and electrochemical properties. Except for 10H type, all LPSO present improved H2 generation features compared to pure Mg. Indeed, 80% of the reaction is achieved in less than 40 minutes. The highest generation yield of 90% is obtained for single phase LPSO Mg87.6Ni5.5Y6.9. Alloys containing both Mg and LPSO beneficiate from galvanic coupling between the two phases leading to higher reactivity. The activation energies of 27.3 and 85.4 kJ/mol determined for Mg91Ni4Y5 (14H + Mg) and Mg83.3Cu7.2Y9.5 (18R) respectively clearly highlight this benefit from galvanic coupling