Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction (ORR) electro-catalysts in MFCs. The rod-like carbon nanotubes (CNTs) were formed on the Fe-N/SLG sheets after a carbonization process. The maximum power density of 1210 +/- 23 mW.m(-2) obtained with Fe-N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst (1080 +/- 20 mW.m(-2)) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe-N/SLG was 3.91 +/- 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electro-chemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene (HCG, a kind of multilayer graphene) and high activity graphene (HAG, a kind of GO) under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs. The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe-N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst. It demonstrates that this kind of Fe-N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.