Table 1.

An overview of currently practiced methods for nitrogen insertion into graphene.

Method	Description	Drawbacks	Example Study
CVD	High temperature furnace up to 1000 °C, vacuum 1 Torr, catalyst, NH3 as nitrogen source, He as shielding gas	Complex instrumentation, very low yield	[27,28]
Arc Discharge	Electric arc discharge conditions, pyridine and ammonia as a nitrogen carrier	Complex instrumentation, difficult to control, very low yield	[29]
Pyrolysis	High temperature pyrolysis of a stolid mixture of GO—urea lattice, respectively	Limited yield, long time high temperature synthesis, application of GO instead of pure graphene	[30]
Heat treating	Heating to 800–1000 °C a solid mixture of GO-nitrogen source, neutral atmosphere, melamine as a potential nitrogen source		[31]
Solvothermal	200–300 °C, 4–5 h duration, dimethylformamide as a solvent and nitrogen source	Yield limited by the experimental vessel volume, use environmentally and health unfriendly reagents	[32]
Gas Annealing	High temperature of 500–1000 °C during electrical annealing of GO in nitrogen atmosphere, ammonia gas (NH3) as a nitrogen source	GO applied instead of pure graphene/graphite, low yield, a high temperature method	[33,34]
N2 Plasma Treatment	Nitrogen content controlled by the plasma strength and exposure time, example plasma generator parameters 40–200 W, 900 V DC bias, high vacuum 200 mTorr, 20–80 min treatment, graphene or GO as a key precursor, N2 and NH3 as nitrogen source	Sophisticated instrumentation and challenging synthesis conditions, low yield	[35]
Dry Ball Milling	Mechanochemical process, room temperature direct grinding of dry powdered graphite in the N2 or NH3 atmosphere, nitrogen content controllable by changing milling parameters	Unwanted insertion of impurities from the grinding setup, which must be removed by additional treatment, laboratory scale process	[36]
Nanoscale High Energy Wet Ball Milling	Mechanochemical process, room to 80 °C wet milling; gas, liquid and solid nitrogen carriers permittable, GO advised as carbon precursor	Complex manufacturing pathway including frequent rising, laboratory scale process	[37]