Improved Hydrogen Generation Performance via Hydrolysis of MgH<sub>2</sub> with Nb<sub>2</sub>O<sub>5</sub> and CeO<sub>2</sub> Doping

Rapid formation of magnesium hydroxide passivation layer during hydrolysis of MgH2 seriously blocks its application as a hydrogen generation material. MgH2 is also susceptible to oxidation. MgH2 with Nb2O5 and/or CeO2 doping has been prepared via high energy ball milling in this work with the aim of enhancing the hydrolysis performance and oxidation resistance. The phase compositions, microstructure and hydrogen evolution properties have been systematically investigated. Nb2O5 and CeO2 particles with particle size in the range of ∼20–200 nm are uniformly dotted on the surface of MgH2 matrix after ball milling. It is found that Nb2O5 shows better facilitating effects than CeO2 on the hydrolysis performance of MgH2. As-milled MgH2+10%Nb2O5 and MgH2+10%CeO2 samples generate ∼705 and 474 mL g−1 of hydrogen in distilled water within 60 min, respectively. Introducing MgCl2 in water can also significantly enhance the hydrolysis reaction kinetics and conversion rate. As-milled MgH2+10%Nb2O5 sample shows a hydrogen yield of 1222 mL g−1 in 5% MgCl2 solution, corresponding to a conversion rate of 74.6%. However, air exposed MgH2+10%Nb2O5 sample hardly generates any hydrogen in MgCl2 solution. CeO2 can modify the oxidation resistance to some extent. MgH2 with CeO2 doping can still produce ∼250 mL g−1 of hydrogen after 24 h air exposure.