I made a graphene suspension ( 100 mg in 100 mL DI water) by sonicating synthetic graphite powder (BET surface area= 10 m2/g ) for 1 h. After the sonication, the graphite BET was 8 m2/g. I calculated the number of layers by XRD, and it equals to 72. Theoretically, I should get 36 m2/g (dividing single layer graphene surface area (2630 m2/g) by 72) for sonicated graphite, but I didn't get it.
Specific surface area (SSA) depends on numerous factors. So, it is very difficult to identify the inherent cause of this low SSA!
Hasara Samaraweera
The two BET surface areas are comparable, indicating your sonication is not effective in exfoliating graphite. Dividing the theoretical surface area of the single-layer graphene is too ideal to get the accurate value. As Islam mentioned, the experimental surface area could be influenced by numerous factors, e.g., sheet aggregation, mechanical damage, and differences in the sheet area (and hence mass), etc.
I just recommended Tianyu Liu's answer also.Your graphene sheets may be broken into small fragments instead of exfoliation with the US power.These tiny graphene fragments are very reactive due to their high dangling bonds.Therefore, chemical or physical reaction can be taken place between those fragments. Read more.....Otherwise, 2 m2/g is not the significant change for the big reason.
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