Nitrogen Doped Graphene Aerogel Inserted By Carbon Black As Novel Catalyst Support for Low Temperature Hydrogen Fuel Cells
Authors: Zhao Ziyu , Ai Ling , Zhou Zeyu , Yang Xiaochen , Zhai Heng , Holmes Stuart 
Published: August 2024

Carbon supported Pt nanocatalysts, which are commonly used in hydrogen fuel cells, suffer from Pt degradation and carbon corrosion. That causes the high cost and limited lifetime of the fuel cell1. Developing catalyst support materials with high surface area, high electrical conductivity, stability and good interaction with catalyst is an effective solution to address this issue.
To enhance the activity and durability of Pt-based catalysts for hydrogen fuel cells, graphene aerogels (GA) are a prospective material with rich porous 3D-structure, large surface area, high electrical conductivity, and good electrochemical stability. They also can improve the tolerance of catalyst CO poisoning and avoid graphene stacking by integrating 2D sheet structure into 3D aerogel structure2, 3. Some research show that the nitrogen doped on the surface of carbon materials could improve ORR activity and electronic conductivity by changing the local electronic structure as well as providing a stable anchor point for pt nanoparticles to enhance the durability of catalysts4, 5.
However, most GAs are made from graphene oxide (GO) produced by Hummers method which may lead to safety and environmental issue due to the usage of highly toxic and corrosive chemicals2, 5. Also, there are few articles on the application of GA in fuel cells. It may be limited by the collapse and loss of pore structure caused by compression in a fuel cell setup.
In this work, graphene oxide produced by electrochemical exfoliation (EGO) was used to prepare N-doped graphene aerogel (NGA) via hydrothermal treatment with ammonia solution as nitrogen source. Moreover, NGA was mixed with carbon black (CB) as a hybrid support material that can avoid collapse of the macropore and generate a graphene-carbon network to provide large surface area for Pt nanoparticles and improve the performance of the fuel cell. Figure1 shows preliminary characterization results of NGA and performance of NGA-CB supported Pt catalysts with different content of NGA. Rich macro-mesoporous structure of NGA can be observed in the SEM image (Figure 1 (a)). Pt catalyst with 20% NGA has a maximum power density of 838 mw cm-2 which is a 31% improvement over that of Pt/CB (Figure 1 (b)).
In conclusion, this study presents a fast, efficient and environmentally friendly way to synthesize nitrogen doped GA. The introduction of NGA into CB as catalyst supports can improve the electrochemical active surface area and performance of fuel cells due to graphene aerogel's high conductivity and porosity. Besides, it is effective to enhance the utilization of Pt and durability of catalysts. This will help to reduce the cost of fuel cells and facilitate their commercialization in various fields of application.
Figure 1 (a) SEM images of dried NGA. (b) Performance of Pt/NGA-CB with various content of NGA compared to Pt/CB catalyst in a hydrogen fuel cell at 60 ℃ with 100% RH.

References

Liu, J.; Wu, X.; Yang, L.; Wang, F.; Yin, J., Unprotected Pt nanoclusters anchored on ordered mesoporous carbon as an efficient and stable catalyst for oxygen reduction reaction. Electrochimica Acta
2019,
297, 539-544.

Sarac Oztuna, F. E.; Barim, S. B.; Bozbag, S. E.; Yu, H.; Aindow, M.; Unal, U.; Erkey, C., Graphene Aerogel Supported Pt Electrocatalysts for Oxygen Reduction Reaction by Supercritical Deposition. Electrochimica Acta
2017,
250, 174-184.

Wu, Z.-S.; Yang, S.; Sun, Y.; Parvez, K.; Feng, X.; Müllen, K., 3D Nitrogen-Doped Graphene Aerogel-Supported Fe3O4 Nanoparticles as Efficient Electrocatalysts for the Oxygen Reduction Reaction. Journal of the American Chemical Society
2012,
134 (22), 9082-9085.

Li, O. L.; Chiba, S.; Wada, Y.; Panomsuwan, G.; Ishizaki, T., Synthesis of graphitic-N and amino-N in nitrogen-doped carbon via a solution plasma process and exploration of their synergic effect for advanced oxygen reduction reaction. Journal of Materials Chemistry A
2017,
5 (5), 2073-2082.

Xie, B.; Zhang, Y.; Zhang, R., Coassembly and high ORR performance of monodisperse Pt nanocrystals with a mesopore-rich nitrogen-doped graphene aerogel. Journal of Materials Chemistry A
2017,
5 (33), 17544-17548

Figure 1