Enhancing hydrogen sorption performances of MgH2 by in-situ introduction of molybdate derived FeMo nano catalysts

The design and construction of efficient catalysts for Mg-based hydrogen storage materials are of great importance for promoting their industrial applications. In the present work, a composite of g-C 3 N 4 (NCN) supported FeMoO 4 was prepared and introduced into MgH 2 as a catalyst precursor through ball milling. As a result of the reaction between FeMoO 4 and MgH 2 , a nano FeMo catalyst formed in-situ and provides excellent catalytic effect on MgH 2 . For instance, the catalyzed Mg/MgH 2 system started to dehydrogenate at about 187 °C, with a total dehydrogenation of 6.1 wt% achieved in 6 min at 275 °C. It can absorb 6 wt% H 2 in 2 min under 3 MPa pressure at 150 °C. Meantime, the hydrogen desorption and absorption activation energy of the composite system dropped down to 85.3 kJ/mol H 2 and 44.72 kJ/mol H 2 , respectively. Furthermore, the presence of g-C 3 N 4 nanosheets (NCN) provides a good nano-separation effect for MgH 2 , and the composite system exhibits high cycling stability (95.3 % capacity retention after 50 cycles) and fast kinetic. Theoretical calculation shows that the interaction between FeMo and MgH 2 weakened the Mg-H bond, thus promoting the decomposition of MgH 2 at lower temperatures. This study provides a new strategy for the design of efficient catalysts with multiple promotion functions for high performance solid-state hydrogen storage materials.