How Does Metal Hydride Formation Occur?

[mess1n]

I'm very confused about how metal hydrides form. I'm looking at PCI plots and I see what's happening, but I have no idea why it is. For instance:

"Molecular hydrogen is dissociated at the surface before absorption; two H atoms recombine to H₂ in the desorption process."

Why does this happen?

Also, I've attached a PCI plot. Can anyone explain why the concentration suddenly increases at certain pressures?

I've searched so many books and internet resources to try and find an explanation for these processes, to no avail, please help! :(


Andrew

 

[mess1n]

Sorry to bump this, but I'm hoping someone sees it who will be able to help. Is this question in the right section?

 

[Astronuc]

There is a theory of autocatalytic dissociation of hydrogen in metals.
http://www.springerlink.com/content/f602850hk808h357/

And there is this
Hydrogen dissociation on metal surfaces – a model system for reactions on surfaces
Applied Physics A: Materials Science & Processing
Volume 67, Number 6, 627-635, DOI: 10.1007/s003390050834
A. Gross

Clearly to form hydrides, the proton has to diffuse through the metallic grains/crystal structure. The solubility of hydrogen in a metal is temperature dependent.

 

[mess1n]

Thanks so much for the reply, I'll read through those articles now.

 

[alphy]

,

Metal hydrides form through a process called hydrogen absorption or hydrogenation. This process involves the reaction of a metal with hydrogen gas to form a metal hydride. The formation of metal hydrides is a complex process and depends on several factors such as the type of metal, temperature, and pressure.

In the case of molecular hydrogen absorption, the gas molecules first interact with the metal surface, causing the hydrogen molecules to dissociate into two H atoms. These atoms then diffuse into the metal lattice and bond with the metal atoms to form metal hydrides. This process is reversible, and at higher temperatures, the metal hydride can release hydrogen molecules through desorption.

The PCI plot you have attached shows the relationship between pressure and concentration of hydrogen in the metal. This plot is typically used to understand the kinetics of hydrogen absorption and desorption. At lower pressures, the concentration of hydrogen in the metal is low, but as the pressure increases, more hydrogen molecules are absorbed by the metal, leading to a sudden increase in concentration. This increase is due to the fact that at higher pressures, more hydrogen molecules are available for absorption, leading to a higher rate of absorption.

I understand that this process can be confusing, but it is essential to note that the formation of metal hydrides is a result of complex interactions between the metal and hydrogen gas. It is also worth mentioning that different metals have different absorption and desorption behaviors, which can also impact the formation of metal hydrides. I suggest consulting with a materials scientist or chemist who specializes in metal hydrides for a more in-depth explanation. I hope this helps clarify some of your confusion.