▎ 摘　　要

The need for the development of metal-free electrocatalysts for oxygen reduction reaction (ORR) has become a necessity to circumvent the prohibitive cost of Pt and the shortcomings of Pt-based catalysts. Herein, for the first time, graphene surface was tuned by a simple, room temperature, and easily adaptable electrochemical approach using ammonium carbamate as a nitrogen precursor. This method efficiently tuned the graphene surface by incorporating nitrogen and nitrogen functionalities with an unprecedented content of nitrogen (22.48%). The surface tuned graphene (N-Gr) acts as an efficient metal-free electrocatalyst towards oxygen reduction reaction in a wide pH range, i.e. from neutral (pH 7) to alkaline (pH 14). Also, the N-Gr exhibits a similar Tafel slope (76 mV/dec) to that of Pt/C (64 mV/dec) in 0.1 M KOH. Long term stability and better tolerance to fuel are the other advantages of the N-Gr. The observed ORR activity of the N-Gr might be due to the higher content of nitrogen which provides higher active sites to promote electron transfer in ORR. All these confirm that the surface tuned graphene can be a suitable electrocatalyst for fuel cell applications and the electrochemical approach may pave a way to develop a set of novel and efficient electrocatalysts using the other graphitic nanocarbons.