Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

Hydrogen production for energy: An overview

Materials for hydrogen-based energy storage – past, recent progress and future outlook

Magnesium based materials for hydrogen based energy storage: Past, present and future

Knowledge and foundational understanding of phenomena associated with the behavior of materials at the nanoscale is one of the key scientific challenges toward a sustainable energy future. Size reduction from bulk to the nanoscale leads to a variety of exciting and anomalous phenomena due to enhanced surface-to-volume ratio, reduced transport length, and tunable nanointerfaces. Nanostructured metal hydrides are an important class of materials with significant potential for energy storage applications. Hydrogen storage in nanoscale metal hydrides has been recognized as a potentially transformative technology, and the field is now growing steadily due to the ability to tune the material properties more independently and drastically compared to those of their bulk counterparts. The numerous advantages of nanostructured metal hydrides compared to bulk include improved reversibility, altered heats of hydrogen absorption/desorption, nanointerfacial reaction pathways with faster rates, and new surface states cap...

Nanostructured Metal Hydrides for Hydrogen Storage.

Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg2 NiH4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg2 NiH4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol-1 ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents.

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

State of the art multi-strategy improvement of Mg-based hydrides for hydrogen storage

Magnesium hydride is considered as an ideal candidate for effective hydrogen storage due to its high gravimetric hydrogen capacity and accessibility. But its use as a commercial material is hindered by its relatively high operating temperatures and slow release/uptake kinetics. To solve this, we first synthesized Ni decorated graphene nanoplate (Ni/Gn) catalysts with highly dispersed metal nano-particles (NPs) via a facile method, then the as-prepared Ni/Gn catalysts were introduced by using the hydriding combustion synthesis and mechanical milling (HCS + MM) method to obtain Mg-based composites. Remarkable enhancement of hydrogen sorption rates has been found for these composites in the presence of Ni/Gn additives, especially for the Mg@Ni8Gn2 sample: a hydrogen absorption amount of 6.28 wt% within 100 s at 373 K and a hydrogen desorption amount of 5.73 wt% within 1800 s at 523 K. A rather low activation energy (71.8 kJ mol−1) for the dehydrogenation of MgH2 was determined in the same sample, indicating that relatively moderate temperatures are required to absorb/desorb hydrogen. The excellent hydrogen sorption rates of the composites are thought to be associated with the high dispersity of in situ formed nanometric Mg2NiH4 particles during the HCS + MM process. In addition, a microstrain-induced synergetic hydrogen sorption mechanism is proposed, being correlated by the local introduction of a Mg2Ni nano-catalyst into the Mg matrix.

Nickel-decorated graphene nanoplates for enhanced H2 sorption properties of magnesium hydride at moderate temperatures

Metal nanocatalysis is an effective method to enhance the hydrogen storage properties of magnesium hydride (MgH2), and the catalytic effect can be further improved by a matrix material supported nanometal. In this work, carbon supported nano-Ni (Ni@C) was synthesized by calcination of dimethylglyoxime dinickel chelate, and then it was doped into MgH2 to improve the de/rehydrogenation kinetics. This shows that the homogeneously distributed Ni with refined particle size in carbon base leads to superior catalytic effects on hydrogen absorption/desorption of MgH2-5 wt % Ni@C. The MgH2-5 wt % Ni@C starts to desorb hydrogen at 187 °C, which is 113 °C lower than that of as-milled MgH2. Moreover, it takes only 500 s to thoroughly desorb hydrogen at 300 °C, which is 3000 s faster than as-milled MgH2 under the same dehydrogenation conditions. According to the Kissinger’s method, the apparent activation energy for desorption of the MgH2-5 wt % Ni@C is 66.5 ± 1.8 kJ mol–1, which is about 79.9 kJ mol–1 lower than that...

Facile Synthesis of Carbon Supported Nano-Ni Particles with Superior Catalytic Effect on Hydrogen Storage Kinetics of MgH2

Catalysts play an extraordinarily important role in accelerating the hydrogen sorption rates in metal-hydrogen systems. Herein, we report a surprisingly synergetic enhancement of metal-metal oxide cocatalyst on the hydrogen sorption properties of MgH2: only 5 wt % doping of Ni into ultrafine TiO2 enables a significant increase in hydrogen desorption kinetics; it absorbs 4.50 wt % hydrogen even at a low temperature of 50 °C. The striking improvement is partially ascribed to the formation of a particular Ni@TiO2 core-shell structure, thereby forming versatile interfaces. This study provides insights into the way of designing high-efficiency catalysts in hydrogen storage and other energy-related fields.

Jiguang Zhang

Papers

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

State of the art multi-strategy improvement of Mg-based hydrides for hydrogen storage

Nickel-decorated graphene nanoplates for enhanced H2 sorption properties of magnesium hydride at moderate temperatures

Facile Synthesis of Carbon Supported Nano-Ni Particles with Superior Catalytic Effect on Hydrogen Storage Kinetics of MgH2

Remarkable Synergistic Catalysis of Ni-Doped Ultrafine TiO2 on Hydrogen Sorption Kinetics of MgH2