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How to -- Reaction rate, platinum catalyst efficiency model
Posted 24 oct. 2017, 09:29 UTC−4 Chemical, Chemical Reaction Engineering, Electrochemistry 6 Replies
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Hi, I am trying to model glucose oxidation to gluconic acid, with an abiotic platinum metal catalyst. So the irreversable reaction includes glucose and water as reacting species with the formation of gluconic acid with two H+ and two electrons. The catalyst in this action would be platinum. I want to calculate the current density, open circuit voltage and the effect of platinum on the oxidation. I started with the reaction engineering module, but not sure on how to continue this? I can have a platinum metal strip and include the reaction engineering model to have the species to react. But I am missing some connection to the story. Any help will be useful.
Thanks Ram.
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Hi
What is the issue where you need Comsol? Mass transfer to the electrode? I suggest you to use the Electrochemistry module, if you have an access to it. It is not necessary but helps a lot. Just remember that the reaction rate r = i/(nF). The problem is that the reaction has a mechanism that affects on the rate law.
BR Lasse
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Hi, Thanks for your reply. I need to know the current density (to perform a cyclic voltammetry) of the platinum electrode when oxidizing glucose. Not complete oxidation, but to gluconic acid.
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Hi
Do you have an access to the electrochemistry module? Which version of Comsol are you using? I can provide a model that is made with the Transport of Diluted Species physics, no reaction enegineering is needed. I suppose that the reaction takes place in water. Hence, water does not need to be considered as a reactant because its concentration does not really vary due to the reaction, it is included in the reaction rate constant.
Because the reaction is irreversible, the rate law is
r = k·[glucose] = I/(2F)
Now, the rate constant k depends on the electrode potential in a way that depends on the reaction mechanism; it is not an easy task. Do you have any literature reference about it? Two electrons cannot be transferred simultaneously but in a cascade, and one of the reaction steps is rate determining with only one electron involved.
Best regards Lasse
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Hi, Thank you for the reply.
I am using v5.3 and have access to echem. There was a model of a 2D glucose sensor which I had referred to, initially. Instead, I am providing a 3D structure and have included a coarse platinum metal catalyst. One of the referred work is here, http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038436.
As you said, the refernce also doesn't mention any on electron transfer nature. So, I started proceeding with including the reaction enginnering module and to perform a cyclic voltammetry on the intended structure. I also referred to the example model of 'fuel_cell_cathode'. And I was also considering water as a rectant. Will refer the model which you can provide.
Thanks in advance, Ram.
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I have to digest this for a while...
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A simple model attached in 1D. The mechanism is hidden in the reaction order according to the attached paper.