Synthesis of Highly Activated Magnesium by Niobium and Tantalum Gel Oxide Catalyst

Abstract

As catalysts to improve the kinetics of the reaction between Mg and H₂, Nb₂O₅, Ta₂O₅, and Nb₂O₅–Ta₂O₅ mixture gels with and without heat treatment were synthesized using simple sol-gel methods. Furthermore, MgH₂ was ball milled to superficially disperse 1 mol% of each oxide for 2 h, which was ten times shorter than that of previous works. All the oxides show catalytic effects on using easier and simpler synthesis processes. The catalysis of Nb oxides is better than that of Ta oxides and mixtures. The as-synthesized Nb₂O₅ gel without heat treatment is the best catalyst and improves hydrogenation kinetics at room temperature. The Nb₂O₅ gel with higher catalysis is further reduced compared to the heat-treated one because the gel oxide is more unstable owing to the lesser network between Nb and O atoms due to the existence of –OH groups. By using gel oxides, highly activated Mg can be synthesized under milder conditions compared with previous cases.

Fig. 4 TG results for the hydrogen absorption of Mg with the prepared oxides.