It depends whether you are using GO, rGO, or normal graphene. If you are using GO, by heating it up you are actually reducing it. Therefore, the surface area you are measuring is not an indicative of the surface area you are actually dealing with. For the case of rGO, again by heating it up you are actually reducing it more.
Anyway, for graphene based materials, doing BET N2 analysis is typically a waste of time and i not a reliable method to measure the surface area.
In materials containing small pores lower than 2nm down to 1 nm BET-N2 surface area is overestimated as a result of capillary condensation at low relative pressures. In the contrast, when pores are smaller than 0.5 nm, which is the case here, the pore volume is hugely underestimated. As a guideline, whenever a type III isotherm is observed during BET experiment, it represents an exteremly weak adsrobate-adsrbent interaction. Furthermore, Adsorption measurements using nitrogen at 77.4 K is difficult, because the filling of 0.5 - 1 nm pores occurs at P/Po of 10-7 to 10-5, where the rate of diffusion and adsorption equilibration is very slow.
As described earlier N2 adsorption method is unable to provide accurate surface area for GO and RGO samples. Therefore methylene blue (MB) dye adsorption in aqueous solution has been used to determine the surface area. Titration method by MB has been used for clay minerals and activated carbon generally by industries for several decades.
You can find how to do these measurements on the supporting information of our paper in ACS Nano where we have compared the results of both methods.
Article High-Performance Multifunctional Graphene Yarns: Toward Wear...
The degassing temperature useful to remove humidity or other absorbed gases can be carried out at 200-250oC. Here it depends whether you want degassing temperature for GO, reduced GO or graphene. GO & RGO contains number of carboxylate or epoxies groups attached to it. Better check the TGA of the sample. But 200-250oC will be the ideal temperature for degassing.
Good explanation by Sundeep Kumar Dhawan Sir,
yes It should be done below it is going to loose it functional groups in case of GO and RGO. For pure graphene some higher temperature may not affect much, and suggested temperature may be suitable.
It depends whether you are using GO, rGO, or normal graphene. If you are using GO, by heating it up you are actually reducing it. Therefore, the surface area you are measuring is not an indicative of the surface area you are actually dealing with. For the case of rGO, again by heating it up you are actually reducing it more.
Anyway, for graphene based materials, doing BET N2 analysis is typically a waste of time and i not a reliable method to measure the surface area.
In materials containing small pores lower than 2nm down to 1 nm BET-N2 surface area is overestimated as a result of capillary condensation at low relative pressures. In the contrast, when pores are smaller than 0.5 nm, which is the case here, the pore volume is hugely underestimated. As a guideline, whenever a type III isotherm is observed during BET experiment, it represents an exteremly weak adsrobate-adsrbent interaction. Furthermore, Adsorption measurements using nitrogen at 77.4 K is difficult, because the filling of 0.5 - 1 nm pores occurs at P/Po of 10-7 to 10-5, where the rate of diffusion and adsorption equilibration is very slow.
As described earlier N2 adsorption method is unable to provide accurate surface area for GO and RGO samples. Therefore methylene blue (MB) dye adsorption in aqueous solution has been used to determine the surface area. Titration method by MB has been used for clay minerals and activated carbon generally by industries for several decades.
You can find how to do these measurements on the supporting information of our paper in ACS Nano where we have compared the results of both methods.
Article High-Performance Multifunctional Graphene Yarns: Toward Wear...
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