Highly active multivalent multielement catalysts derived from hierarchical porous TiNb2O7 nanospheres for the reversible hydrogen storage of MgH2

Critical limitations in applying MgH(2)as a hydrogen-storage medium include the high H(2)desorption temperature and slow reaction kinetics. In this study, we synthesized hierarchical porous TiNb(2)O(7)spheres in micrometer scale built with 20-50 nm nanospheres, which showed stable activity to catalyze hydrogen storage in MgH(2)as precursors. The addition of 7 wt.% TiNb(2)O(7)in MgH(2)reduced the dehydrogenation onset temperature from 300 to 177 degrees C. At 250 degrees C, approximately 5.5 wt.% H(2)was rapidly released in 10 min. Hydrogen uptake was detected even at room temperature under 50 bar hydrogen; 4.5 wt.% H(2)was absorbed in 3 min at 150 degrees C, exhibiting a superior low-temperature hydrogenation performance. Moreover, nearly constant capacity was observed from the second cycle onward, demonstrating stable cyclability. During the ball milling and initial de/hydrogenation process, the high-valent Ti and Nb of TiNb(2)O(7)were reduced to the lower-valent species or even zero-valent metal, whichin situcreated multivalent multielement catalytic surroundings. A strong synergistic effect was obtained for hybrid oxides of Nb and Ti by density functional theory (DFT) calculations, which largely weakens the Mg-H bonding and results in a large reduction in kinetic barriers for hydrogen storage reactions of MgH2. Our findings may guide the further design and development of high-performance complex catalysts for the reversible hydrogen storage of hydrides.

Automated summary

The study successfully reduced the dehydrogenation onset temperature of MgH(2) by synthesizing TiNb(2)O(7) composite oxide catalyst, achieving more efficient hydrogen storage and release. Additionally, the catalyst exhibited stable performance at low temperatures and good cycling stability.