25 mL of the above GO suspension was further dispersed into 175 mL of H2O by ultrasonication for 5 min. Then, the solution was put into a refrigerator and cooled down to 0-5 degC, which was followed by the addition of pyrrole (Sigma-Aldrich 1 mL). After that, the suspension was concentrated to approximately 30 mL by filtration, which was further dried by vacuum freeze-drying. Then, the as-prepared product (Go-Ppy) was pyrolysed at 500 degC, 700 degC, and 900 degC for 1 h under an Ar atmosphere, yielding the final products (designated as G-NCs-5, G-NCs, and G-NCs-9). Graphene (G) and nitrogen-doped carbon (NC) were prepared via the same process only without the addition of pyrrole and graphene, respectively.
GO suspension
dispersed
25 mL
mL
H2O
175 mL
mL
GO suspension
ultrasonication
5 min
min
pyrrole
addition
1 mL
mL
solution
cooled down
0-5 degC
degC
suspension
concentrated
30 mL
mL
product
pyrolysed
500 degC, 700 degC, and 900 degC
degC
Go-Ppy
pyrolysed
1 h
h