Significantly improved hydrogen storage behaviors in MgH2 with Nb nanocatalyst

The study explores the excellent modification effect of Nb nanocatalyst prepared via surfactant assisted ball milling technique (SABM) on the hydrogen storage properties of MgH2. Optimal catalyst doping concentration was determined by comparing onset decomposition temperature, released hydrogen capacity, and reaction rate for different MgH2-ywt%Nb (y = 0, 3, 5, 7, 9) composites. The MgH2-5wt%Nb composite started releasing hydrogen at 186.7 degrees C and a total of 7.0wt% hydrogen was released in the dehydrogenation process. In addition, 5wt% Nb doped MgH2 also managed to release 4.2wt% H-2 within 14 min at 250 degrees C and had the ability to absorb 4.0wt% hydrogen in 30 min at 100 degrees C. Cycling tests revealed that MgH2-5wt%Nb could retain 6.3wt% H-2 storage capacity (89.2%) after 20 cycles. Dehydrogenation and hydrogenation activation energy values were decreased from 140.51 +/- 4.74 and 70.67 +/- 2.07 kJ center dot mol(-1) to 90.04 +/- 2.83 and 53.46 +/- 3.33 kJ center dot mol(-1) after doping MgH2 with Nb, respectively. Microstructure analysis proved that homogeneously distributed NbH acted as active catalytic unit for improving the hydrogen storage performance of MgH2. These results indicate SABM can be considered as an option to develop other nanocatalysts for energy related areas.