Related Experiment Video
Updated: May 9, 2025
09:05
Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials
Published on: May 15, 2015
14.7K
Synthesis and Hydrogen Storage Properties of Mg-Based Complex Hydrides with Multiple Transition Metal Elements
Evans Pericoli1, Alessia Barzotti1, Raffaello Mazzaro1,2
1Department of Physics and Astronomy "Augusto Righi", University of Bologna, Bologna 40127, Italy.
ACS Applied Energy Materials
|May 2, 2025
Summary
New complex hydrides based on magnesium and transition metals (Mg2TMHn) show promising reversible hydrogen storage capacities. Their performance depends on the Mg/TM ratio and transition metal composition, with phase segregation impacting long-term stability.
Area of Science:
- Materials Science
- Hydrogen Storage
- Solid-State Chemistry
Background:
- Magnesium-based complex hydrides are explored for hydrogen storage applications.
- Transition metals (TM) can form complex hydrides with magnesium, influencing hydrogen storage properties.
- Understanding the synthesis and hydrogen storage behavior of Mg2TMHn is crucial for developing advanced materials.
Purpose of the Study:
- To synthesize Mg2TMHn complex hydrides using reactive ball milling.
- To investigate the structural and hydrogen storage properties of these hydrides with varying TM compositions and Mg/TM ratios.
- To evaluate the reversible hydrogen storage capacity and identify factors affecting performance.
Main Methods:
- Synthesis via reactive ball milling of Mg and TM powders under H2 pressure.
- Structural characterization using X-ray diffraction (XRD).
- Hydrogen content determination by temperature-programmed desorption (TPD).
- Reversible hydrogen storage evaluation using pressure-composition isotherms in a Sieverts-type apparatus.
- Microstructural analysis using transmission electron microscopy (TEM) with nanoscale microanalysis.
Main Results:
- Single fcc Mg2TMHn hydride phase (K2PtCl6-type structure) formed for Mg/TM ratio of 2:1.
- Tetragonal MgH2 also observed for Mg/TM ratio of 3:1.
- Maximum initial hydrogen content of ~5 wt% for 3:1 samples.
- Similar onset desorption temperatures regardless of TM composition, indicating no significant destabilization by Cr or Mn.
- Reversible gravimetric capacity of 3.7-4.2 wt% for 3:1 samples and 3.0-3.2 wt% for 2:1 samples within the tested window.
- Phase segregation of transition metals (especially Cr and Mn) observed, correlating with decreased reversible capacity.
Conclusions:
- Mg2TMHn complex hydrides can be synthesized by reactive ball milling.
- Reversible hydrogen storage is achieved through Mg-MgH2 and Mg2TM-Mg2TMHn transformations.
- The Mg/TM ratio significantly impacts reversible capacity, with 3:1 ratios showing higher performance.
- Phase segregation of transition metals is a key factor limiting long-term reversible hydrogen storage capacity.
Related Concept Videos
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
295
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
295
02:42Valence Bond Theory
8.3K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
8.3K
01:23Properties of Organometallic Compounds
847
Organometallic compounds are compounds that contain a carbon–metal bond. Carbon belongs to an organyl group like alkyl, aryl, allyl, or benzyl groups. The metal can be from Group I or Group II of the periodic table, a transition metal, or a semimetal.
847
03:02Colors and Magnetism
11.3K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
11.3K
02:58Properties of Transition Metals
24.4K
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
24.4K
02:51Metal-Ligand Bonds
20.4K
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
20.4K