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Magnesium hydride $(\ce{MgH2})$ is a metal hydride with a relatively stable structure, at least compared to other metal hydrides. Magnesium hydride splits at around 300 °C into magnesium and hydrogen. The decomposition temperature can be halved with a catalyst.

Unfortunately, these catalysts are often titanium-based (example A and example B), which does not make this a realistic way to reduce the temperature required, at least not if made for wide-spread production, as titanium is a rare and expensive metal.

What catalysts are proven and effective at reducing the temperature required to break magnesium hydride, that don't include titanium?

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    $\begingroup$ I would consider titanium neither rare nor expensive. Titanium is ninth most abundant element on Earth, and is much cheaper than other transition metals used as catalysts. My friend used to ride a bicycle with titanium frame (aquired about 20 years ago) before switching to carbon fiber, and he is no Rockefeller. $\endgroup$
    – andselisk
    Commented Oct 10, 2022 at 5:04
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    $\begingroup$ The only aspect somewhat affecting price is technologically demanding production of bulk metallic titanium, due its high affinity of oxygen and high melting point. $\endgroup$
    – Poutnik
    Commented Oct 10, 2022 at 8:00

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From Shikin et al.[1], a recommendation to press the magnesium hydride with nickel powder:

We have studied the activation of magnesium hydride decomposition by means of its pressing with a catalyst. It is established that pressing leads to the formation of metal nuclei, which favor a decrease in the temperature threshold of magnesium hydride decomposition. The introduction of catalytic additives also reduces the temperature of dehydrogenation. The most effective in this respect was found to be the addition of nickel powder.

Reference*

  1. Shikin, I.V., Elets, D.I., Voyt, A.P. et al. (2017). "Activation of magnesium hydride by pressing with catalytic additives." Tech. Phys. Lett. 43, 190–193. https://doi.org/10.1134/S1063785017020262.
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It's seems like the cheapest catalyst to ease this decomposition is $\ce{MgO}$ (Ref.1):

MgO effect on MhH2 decomposition

Other metal catalysts, which effect this decomposition are as follows:

Correlation between the desorption temperature of hydrogen upon oxide addition

Evidently, $\ce{MgO}$ seemingly better metaloxide than titanium oxides as well as the best metal catalyst so far, $\ce{Nb2O5}$.

References:

  1. José-Ramón Ares-Fernández, and Kondo-Francois Aguey-Zinsou, "Superior $\ce{MgH2}$ Kinetics with $\ce{MgO}$ Addition: A Tribological Effect," Catalysts 2012, 2(3), 330-343 (DOI: https://doi.org/10.3390/catal2030330).
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