Few-layer versus mono-layer N-doped graphenes in oxygen reduction reaction

[Display omitted] •N-doped few-layer (N-Gr) and mono-layer (N-gr) graphene samples.•Comparable high doping degree for both graphenes.•N-Gr particles are more ordered due to graphitic nitrogen and presence of vacancies in N-gr.•N-Gr is more active in ORR due to increased electron density and negative shift of the flat-band potential. Doped graphenes, nitrogen-doped (N-doped) in particular, are known to possess promising electrocatalytic performance in oxygen reduction reaction (ORR). We study the effect of the structure of N-doped few-layer (N-Gr) and mono-layer (N-gr) graphenes prepared within one low-temperature approach on their functional behavior as ORR electrocatalysts. Spectral studies reveal the nitrogen content in N-Gr being a quarter greater than in N-gr and nearly one third of all nitrogen atoms in N-Gr being within graphitic fragments, while about half of all nitrogen atoms of N-gr are pyrrolic ones; N-Gr particles are characterized by the presence of defects at the edges, while vacancies are also characteristic of N-gr. It is established that the structural differences of N-Gr and N-gr determine higher electrocatalytic performance of N-Gr in ORR and its four-electron mechanism, which are associated with a significant increase in the charge carrier density and shift of the flat-band potential to negative potential range. The significance of the work is directly related to practical application, since N-Gr could be prepared by fundamentally simpler method, its preparation is ecologically friendly, easily scalable and, therefore, cost effective.