Realizing Hydrogen De/Absorption Under Low Temperature for MgH2 by Doping Mn-Based Catalysts

Abstract

Magnesium hydride (MgH2) has been considered as a potential material for storing hydrogen, but its practical application is still hindered by the kinetic and thermodynamic obstacles. Herein, Mn-based catalysts (MnCl2 and Mn) are adopted and doped into MgH2 to improve its hydrogen storage performance. The onset dehydrogenation temperatures of MnCl2 and submicron-Mn-doped MgH2 are reduced to 225 °C and 183 °C, while the un-doped MgH2 starts to release hydrogen at 315 °C. Further study reveals that 10 wt% of Mn is the better doping amount and the MgH2 + 10 wt% submicron-Mn composite can quickly release 6.6 wt% hydrogen in 8 min at 300 °C. For hydrogenation, the completely dehydrogenated composite starts to absorb hydrogen even at room temperature and almost 3.0 wt% H2 can be rehydrogenated in 30 min under 3 MPa hydrogen at 100 °C. Additionally, the activation energy of hydrogenation reaction for the modified MgH2 composite significantly decreases to 17.3 ± 0.4 kJ/mol, which is much lower than that of the primitive MgH2. Furthermore, the submicron-Mn-doped sample presents favorable cycling stability in 20 cycles, providing a good reference for designing and constructing efficient solid-state hydrogen storage systems for future application.

Enhanced Hydrogen Storage Performance of MgH2 by the Catalysis of a Novel Intersected Y2O3/NiO Hybrid

“…When the temperature reaches 275 • C, 3.7 wt% H 2 is already released, and following a 15-min dwelling, a capacity of 6.0 wt% is reached. This isothermal property is comparable to that of Mn-doped MgH 2 system [50]. In addition, a total amount of 6.6 wt% H 2 is released when the isothermal period is further extended to 60 min.…”

“…The system with 5 wt% Y 2 O 3 /NiO addition can release more amount of hydrogen compared with the others when the dehydrogenation temperature is over 320 • C, and a capacity of 6.8 wt% H 2 is achieved upon heating to 350 • C. The peak dehydrogenation temperatures of the systems obtained by making the differentiation of the dehydrogenation curves is highly consistent with the TPD results as shown in Figure S2a. The onset dehydrogenation temperature of the present MgH 2 doped with 10 wt% Y 2 O 3 /NiO is comparable with that of a Mn-doped MgH 2 system [50] and is 35 and 50 • C lower than those of the FeCoNi@GS doped [51] and HfCl 4 doped [52] MgH 2 systems, respectively. Moreover, the amount of hydrogen released upon heating to 300 • C of the present work (5.2 wt% H 2 ) is also much higher than that of the two works, where the FeCoNi@GS doped MgH 2 system only shows a dehydrogenation capacity less than 3 wt% at the same temperature.…”

Review on Hydrogen Storage Performance of MgH2: Development and Trends

“…Submicron Mn as catalyst has also been applied to improve the hydrogen storage performance of MgH 2 , MgH 2 +10 wt % Mn composite material can reduce the dehydrogenation temperature to 183 °C. 6.6 wt % H 2 could be rapidly released within 8 min under the condition of 300 °C, and nearly 3.0 wt % H 2 can be rehydrogenated within 30 min under the condition of 100 °C and 3 MPa [15] . R. R. Shahi et al [16] .…”

Improvement of Mg‐Based Hydrogen Storage Materials by Metal Catalysts: Review and Summary

“…Apart from Ni, Ti, Fe, Co, many other transition metal catalysts have been developed to improve the hydrogen storage performance of MgH 2 , including Nb [29c,35] , V [29c, 34,36] , Zn [37] , Mn. [38] All these metal catalysts show excellent catalytic performance. Tong et al [35] prepared Mg-7.5 wt % Nb nanocomposites by hydrogen plasma-metal reaction (HPMR) method.…”

“…Furthermore, the submicron manganese doped samples showed good cycle stability in 20 cycles, and there was no obvious decline in hydrogen storage capacity. [38]…”