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Highly Crystallized Fe2P Embedded in N‑Doped Carbon for Enhancing Long-Term Bioelectricity Generation by Lowering Cathode Poisoning in Microbial Fuel Cells

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posted on 08.07.2020, 17:13 by Peng Zhang, Zhuang Cai, Shijie You, Fangyu Wang, Ying Dai, Yuan Lv, Yanhong Zhang, Nanqi Ren, Jinlong Zou
The air cathode of microbial fuel cells (MFCs) facing wastewater is easily coated with microbes to cause catalyst poisoning, resulting in the serious decline of electricity generation and wastewater purification. Herein, iron phosphide (Fe2P)-embedded nitrogen-doped carbon (Fe2P/NPGC) composites are obtained as cathode [oxygen reduction reaction (ORR)] catalysts to enhance the resistance to catalyst poisoning to ensure the long-term stability of bioelectricity generation in MFCs. MFCs with the Fe2P/NPGC (850 °C) catalyst cathode can obtain a maximum power density of 1.050 W m–2, which is higher than that of commercial Pt/C (0.952 W m–2). After 1900 h of operation, the decline of power density is only 1.967% in MFCs with the Fe2P/NPGC (850 °C) cathode, while the decline of Pt/C is 18.77%. The well-crystallized Fe2P embedded in NPGC can improve the ORR activity and the generation of strong oxidizing substances (OH and O2–) to oxidize the poisoning substances and inhibit the attachment of biofilms to improve the ORR stability. The N-doped carbon structure with good electrical conductivity should lower the charge transfer resistance to reduce energy loss during ORR. The particle-embedded structure of Fe2P/NPGC (850 °C) not only improves the durability of active sites but also boosts the reduction of O2 and/or ORR-related intermediates via a four-electron process. Therefore, the hexagonal Fe2P can be used as a promising active component for obtaining high ORR activity/stability in air cathode MFCs.

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