Ultrafine N-Doped Carbon Nanoparticles with Controllable Size As High Performance Electrocatalysts for Oxygen Reduction Reaction
Authors: Shi Yang , Wang Wenxi , Li Mingchan , Wu ShaoFei , Lyu Fucong , Shang Chaoqun , Lu Zhouguang 
Published: February 2020

The oxygen reduction reaction (ORR) is an essential reaction for energy applications such as fuel cells and metal-air batteries. There are several drawbacks to the current ORR involving the kinetically sluggish process and expensive catalysts which impede the mass production of noble-metal materials for application in clean and efficient energy conversion devices. Herein, a type of ultrafine carbon nanoparticle with high nitrogen doping concentration can be simply prepared from a conveniently available precursor through a green and cost-effective hydrothermal process with sterculia scaphigera as the precursor, which is abundantly available and a constantly renewed natural source. With the aid of water, not only is the product’s specific surface area enlarged, but the pore structure is also enriched, and there is improvement in the degree of graphitization and nitrogen-doped content. 1 Meanwhile, the size of the carbon particle can be readily tuned to a nanoscale by changing the duration of the hydrothermal reaction.2 Interestingly, electrocatalytic activity is dramatically enhanced with the transformation of the carbon size and nitrogen structure. Further considering the effect of temperature on the structural and functional properties, the carbon material treated at 900 oC serves as an optimal ORR electrocatalyst with high selectivity, remarkable stability and excellent methanol tolerance in comparison to the commercial 20% Pt/C electrode in alkaline and acidic media. This kind of carbon material may be a promising alternative for costly Pt-based electrocatalysts in fuel cells. The characterizations reveal that we have achieved a highly satisfactory electrocatalytic activity for ORR, a relatively positive onset potential of -0.02 V (vs. Hg/HgO) in alkaline media and 0.55 V (vs. Ag/AgCl) in acidic media, a higher diffusion-limiting current density than that of Pt/C, as well as outstanding stability and superior tolerance durability to methanol. The preparation method validated in this study responds to the requirement to produce high quality and outstanding performance carbon-based electrocatalysts. Both the simplicity of the operation and the employed biomass precursor exactly meet the criteria for significant cost-saving, easy scale-up and eco-friendly demands for energy storage.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (21001117), the Starting-Up Funds of South University of Science and Technology of China (SUSTC) through the talent plan of the Shenzhen Government and the Shenzhen Peacock Plan (KQCX20140522150815065). S.Y. thanks the support from the Guangdong and Shenzhen Innovative Research Team Program (No. 2011D052, KYPT20121228160843692),Special Funds for the Cultivation of Guangdong Collage Student's Scientific and Technological Innovation ("Climbing Program" Special Funds)

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Figure 1