Synthesis of nitrogen-doped graphene catalyst by high-energy wet ball milling for electrochemical systems

Platinum group metal-based (PGM) catalysts are widely applied in many electrochemical systems such as fuel cells or metal–air batteries because of their excellent catalytic performance. But the high raw material cost of PGM catalysts has become a significant issue. In recent years, huge efforts have been made to reduce the material cost of electrochemical systems by developing non-PGM catalysts, and as one of the promising non-PGM catalysts, nitrogen-doped graphene (N-G) has emerged. In this research, nanoscale high-energy wet ball milling methodology was investigated as an effective synthesis method for N-G catalysts by using graphene oxide and melamine as raw materials. The main purpose is to study reaction mechanism of the synthesis process and the physical, chemical, and electrochemical properties of N-G catalysts generated by this mechanochemical approach. The elemental composition, chemical bonding composition, and electron transfer number of the synthesized products were characterized. The results show that the electron transfer number of the N-G catalyst with 23.2 at% nitrogen doping content, synthesized by the high-energy wet ball milling method, has attained a value of 3.87, which is close to the number (3.95) of Pt/C catalysts, and the grinding time was found to be a significant factor in the properties of N-G catalysts in the experiments. The results also show that the high-energy wet ball milling developed in this research is a promising method to synthesize high-performance N-G catalysts with a simple and easy controllable approach.