TEM studies of Nb2O5 catalyst in ball-milled MgH2 for hydrogen storage

Hydrogen Storage Properties and Structure of Magnesium-Based Alloys Prepared with Melt-Spinning Technique

“…These results are, however, in contradiction to recent TEM studies (Hanada et al, 2008;Porcu et al, 2008), which claim that MgH2 is readily decomposed to Mg even at room temperature by the electron beam irradiation during observation. In these studies, ball-milled MgH2 sample doped with Nb2O5, which exhibits excellent hydrogen reactivity, is used in contrast to our melt-spun ternary alloy.…”

Catalytic Effect of Nb2O5 in MgH2-Nb2O5 Ball-Milled Composites

“…When we performed the fast Fourier transformation (FFT) and the inverse fast Fourier transformation (IFFT) on the selected area near the edge of Nb 2 O 5 particle, we obtained the lattice image with the d-spacing of 2.13Å, which matches the value of MgNb 2 O 3.67 (100). The existence of this ternary phase has also been reported elsewhere [15,21]. Nevertheless, the results so far still can not draw a clear conclusion on the catalytic effect of this ternary phase.…”

“…In the recent Transmission Electron Microscope (TEM) observations on MgH 2 -Nb 2 O 5 ball-milled composites, the size of both the hydride and the additive was found to be within nanoscale. The refinement of size and the consequently homogeneous distribution may lead to the fast kinetics [14,15]. The second possibility comes to the phase changes of Nb 2 O 5 brought by high energy ball-milling.…”

“…The results showed that Nb 2 O 5 had been reduced by ball-milling with MgH 2 for 20 h. Therefore, they suggested that the improvement of desorption properties was caused by the catalytic effect of reduced niobium oxides [16]. Meanwhile, some complex compounds, such as MgNb 2 O 3.67 , have been discovered by another group [15]. Finally, the increased defects in the ball-milled composites may act as the hydrogen pathway facilitating the transportation of hydrogen.…”

Microscopic Study on Hydrogenation Mechanism of MgH₂ Catalyzed by Nb₂O₅

“…11,15) Recent TEM observations also revealed that the catalyst embedded in MgH 2 within nanoscale, 16) causing difficulty in the detection under XRD. After desorption, only Mg and a small amount of MgO were detected, indicating that MgH 2 was dehydrogenated completely.…”