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

Abstract

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. Copyright © 2016 John Wiley & Sons, Ltd.

Nitrogen-doped graphene catalysts: High energy wet ball milling synthesis and characterizations of functional groups and particle size variation with time and speed

“…The characterization results confirm that N‐G catalysts were efficiently synthesized under room temperature and water environment with NHEW ball milling approach. The ORR test result from rotating ring disk electrode (RRDE) method in Figure shows that the ORR electron transfer number of the new synthesized N‐G catalyst has reached to 3.87, which is comparable to 3.95 of the 10 wt% Pt/C catalyst …”

“…Because of these advantages, the ball milling method is a feasible and promising approach for the lab‐scale or industrial‐scale production. Based on the research of ball milling, a new nanoscale high energy wet (NHEW) ball milling is first introduced as a primary synthesis approach for N‐G catalysts in conjunction with the research work previously published . A water reaction environment was applied to the environment of the reaction between graphene oxide (GO) and melamine for the synthesis of N‐G catalysts.…”

“…The purpose of using deionized water as the reaction environment is to well disperse GO and melamine to increase the amount of doped nitrogen in N‐G catalysts, reduce the wear rate of the reactor and grinding media, and enhance the grinding efficiency. Several N‐G catalysts were generated by NHEW ball milling and characterized in the research work previously published . The problems from sintering, overheating, and high‐temperature safety issues were not observed during the synthesis process.…”

“…Electron transfer number of N‐G catalyst samples and the 10 wt% Pt/C catalyst [Colour figure can be viewed at wileyonlinelibrary.com]…”

Electrode Design for Lithium–Sulfur Batteries: Problems and Solutions

“…Ball milling can not only refine the particle size to produce novel and abundant surface, but also break and/or reconstruct various chemical bonds for bringing diverse atoms and functional groups. [ 78 ] Despite some inherent shortcomings such as nonuniform size of synthesized particles and pollution of samples by balls and jars, the ball‐milling method undoubtedly is a simple and practical method for large‐scale production of sulfur‐based cathode materials. [ 74 ] For example, Zhu et al [ 79 ] prepared multifunctional fly ash/sulfur (FA/S) composites as binder‐free cathode of LSBs via one‐step ball milling method ( Figure a).…”