what properties should a particular metal pocess to have maximum OER HER activity
Hi!
It is really tough to define which property actually controlling the kinetics of OER and HER. But primarily, we should look first to the Gibbs free energy of adsorption of the intermediates at the surface which further define the catalytic activity of a material towards OER and HER.
Sharing one article, might be helpful:
https://pubmed.ncbi.nlm.nih.gov/28082532/
And yes! Strongly agree with Prof. Geletii.
Thanks!
Lalita
Dear Nouman,
many thanks for sharing this very interesting technical question with the RG community. First of all I fully agree with the statement by Yurii V Geletii. We are synthetic chemists, so I'm not a proven expert in catalysis. However, to my knowledge the behavior of heterogeneous catalysts in certain reactions is still largely based on trial and error. For a very instructive overview of the various catalysts used in OER and HER reactions please have a look at the following useful review article:
Recent Progresses in Electrocatalysts for Water Electrolysis
Article Recent Progresses in Electrocatalysts for Water Electrolysis
The paper has been pubblished Open Access and is freely available on the internet (please see attachment).
In this context it is interesting to note that last year researchers reported the surprising finding that certain bifunctional catalysts can catalyze both the HER and OER reactions. For more information about this finding please see the following very interesting article:
Bifunctional HER/OER or OER/ORR Catalytic Activity of Two-Dimensional TM3(HITP)2 with TM = Fe–Zn
Article Bifunctional HER/OER or OER/ORR Catalytic Activity of Two-Di...
Unfortunately this paper has not yet been posted as public full text on RG. However, three of the authors have RG profiles. Thus chances are that you can request the full text e.g. from the corresponding author via RG.
Good luck with your work and best wishes, Frank Edelmann
It can be simply explained with the following: The active sites of such a metal should bind the key intermediates with an optimal bond energy that will allow the product O2 or H2 to leave the catalyst surface after the oxidation or reduction already occured in OER and HER, respectively. If the key intermediated are adsorbed or bound too week, they will leave the surface before the oxidation or reduction process occurs. Contrary, if they are bound too strong, they won’t leave the surface and this is know as catalyst poisoning.
Dear Rafique... this is a very subjective question and past several decades the discussion/arguments are on. So many reports with divergent opinion. However, a general understanding that (for OER) the metals which can have more than one oxidation states with optimum adsorption/desorption energy of reaction intermediates. But this is difficult to have in one system so people preferably uses alloy to control the adsorption energies by tuning d-band centre, while selecting the metals for alloy kindly take care of electronegativity differences as well as their individual oxygen interaction properties. I do not know how much helpful this answer is? By the way please have a read of one of very interesting paper from Netherlands "The tale of two Tafel slopes" you can also see this paper where importance of oxidation states is carefully discussed ACS Appl. Mater. Interfaces 2020, 12, 12, 13888–13895.
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