Effect of RE-O/C catalyst on the hydrolysis kinetics and catalytic mechanism of MgH2

Abstract

The reaction between MgH2 and water produces a significant amount of hydrogen gas, which is beneficial for the development of hydrogen energy in fuel cells. However, the slow hydrogen production rate and the formation of a dense Mg(OH)2 layer limit its application. In this study, MgH2 was doped with 2 wt%, 4 wt%, and 8 wt% of RE-O/C (RE-O = La2O3, CeO2, Pr6O11) catalysts through ball milling technology, and hydrolysis experiments were conducted. The hydrolysis kinetics and activation energy were analyzed using Avrami-Erofeev and Arrhenius equations for linear fitting. X-ray diffraction and scanning electron microscopy were employed to analyze the hydrolysis mechanism and the effect of the catalysts on particle surfaces. Notably, the addition of 4 wt% RE-O/C exhibited the best improvement in the hydrolysis performance of MgH2. At high temperatures, the maximum hydrogen production rates for MgH2+4La2O3/C, MgH2+4CeO2/C, and MgH2+4Pr6O11/C are 32.05, 30.92, and 29 mL·g−1·s−1, respectively, with maximum hydrogen capacities of 1996, 2140, and 2000 mL·g−1, and activation energies of 21.8, 24.8, and 21.3 kJ·mol−1, respectively. The MgH2+RE-O/C composites studied overcame the key issues of MgH2 hydrolysis, presenting a promising strategy for hydrogen production.