Why is Area under Desorption Curve (TPD) the total particles desorbed?

AI Thread Summary
In the discussion about Temperature Programmed Desorption (TPD), a key point is the interpretation of the graph plotting desorption rate against temperature. The area under the curve represents the total number of particles desorbed, despite the units appearing to suggest otherwise. This is clarified by understanding that the temperature in the graph functions as a time factor, as the desorption rate varies with temperature and is influenced by the duration spent at each temperature step. Reframing the graph to show desorption rate against time helps clarify the integration results. Additionally, a resource on the choice of adsorptive for physisorption experiments is provided for further reading.
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I'm currently reading about Temperature Programmed Desorption (TPD) and is wondering why in the graph of desorption rate (molecules/cm2/sec) against temperature (deg C), the area under the curve is the total number of particles desorbed? Isnt the units (molecules/cm/sec/degC) if u integrate the curve?
 
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I think you’ll find it’s because although it is plotted against temperature, the temperature is really a factor of time. The desorption rate isn’t constant at each temperature, and the curve is dependent on the time spent at each previous temperature step.

So if you think of the graph as desorption rate against time (s) instead, then it become clear why the integration result isn’t what you expect.

I hope that helps. Also, here is an article on choice of adsorptive which you may find interesting:
http://www.quantachrome.co.uk/en/Adsorptives_for_Physisorption_Experiments.asp
 

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