Nitrogen-doped graphene prepared by a millisecond photo-thermal process and its applications

Abstract

Doping graphene with heteroatoms such as nitrogen is a significant strategy to improve its electrochemical performance. Here, a unique millisecond photo-thermal process which is simple, safe for preparing N-doped Graphene (NG) under ammonia atmosphere was adopted. The obtained NGs were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectra, Scanning Electron Microscope (SEM), and electrochemical techniques. The nitrogen content of the NG can as 14 times as that of original rGO according to the XPS results. The intensity ratio of D band to G band in Raman spectra is increased from 1.12 to 1.18, which also demonstrates the doping of nitrogen atoms and creation of some structure defects. The SEM picture clearly demonstrates that the space between graphene planes was significant enlarged. Furthermore, nitrogen adsorption/desorption test indicated that the specific surface area of NG (267.3 m2 g−1) is much higher than that of original rGO (198.9 m2 g−1), which indicates more surfaces are available after photo-thermal process. The electro-catalysis activity of the NG was characterized by electrochemical reduction of hydrogen peroxide (2 electron process) and oxygen (4 electron process). The hydrogen peroxide reduction potential at the NG electrode was 200 mV positive shift and the peak current increase 15 times compare to bare glassy carbon electrode. The oxygen reduction reaction (ORR) testes shows an obvious reductive peak in −0.39 V vs Ag/AgCl on the NG electrode, which demonstrated that the NG also has the catalysis effect on four-electron process. As well as that, the obtained NG was also used to assemble supercapacitances, it was found that the specific capacitance of NG achieved as high as 350 F g-1 with well cyclic stability and rate capability.