I have no idea about reaction, which occur between ZnO and H2 molecules...
Generally H2 is non reactive at room temperature. It reacts at elevated temperatures. Whenever, ZnO is exposed to H2 at high temperatures, It reacts with Oxygen and make H2O and creates the Oxygen vacancies (OV). As a result of reduction process, optical and electrical properties of ZnO are improved. Furthermore, it could have a strong effect on the morphology of the material.
yes sir i ma agree with u... but at room temperature? how it react with H2???? why its resistance increased when attached on CNTs?
One method suggested in the literature is as follows: Oxide anions (O2)- are adsorbed onto the surface of ZnO. When H2 is introduced, it can react with these anions:
2H2 + (O2)- 2H2O + e-
The electrons produced in this reaction result in a reduction in the surface charge depletion and increase the conductivity of the ZnO.
My guess is that the MWCNTs are used as a template on to which ZnO is deposited to give a very high surface area and maximise the sensing capability?
sir, i am totally agree with u, as u said the conductivity of ZnO increased after H2 adsorption, but how the resistance of MWCNTs/ZnO sensor is increased?
I'm not clear what you mean. Do you mean that the resistivity of the MWCNTs/ZnO sensor increases after H2 adsorption? Or that the resistivity of the MWCNTs/ZnO sensor is higher than that of the ZnO?
I mean that the resistivity of the MWCNTs/ZnO sensor increases after H2 adsorption.. why???
In that case, I don't know. For the same mechanism to cause an INCREASE in resistivity would imply hole (semi)conduction in the MWCNTs, so that adding electrons decreases the number of available charge carriers. That's purely speculation, however - I don't know enough about conduction in MWCNTs to say anything more. I suspect the true answer is more complicated!
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