Metallic State FeS Anchored (Fe)/Fe₃O₄/N-Doped Graphitic Carbon with Porous Spongelike Structure as Durable Catalysts for Enhancing Bioelectricity Generation

Abstract

The critical issues in practical application of microbial fuel cells (MFCs) for wastewater treatment are the high cost and poor activity and durability of precious metal catalysts. To alleviate the activity loss and kinetic barriers for oxygen reduction reaction (ORR) on cathode, (Fe)/FeO/FeS/N-doped graphitic carbon ((Fe)/FeO/FeS/NGC) is prepared as ORR catalyst through a one-step method using waste pomelo skins as carbon source. Various characterization techniques and electrochemical analyses are conducted to illustrate the correlation between structural characteristics and catalytic activity. MFCs with Fe/FeO/FeS/NGC (900 °C) cathode produces the maximum power density of 930 ± 10 mW m (Pt/C of 489 mW m) and maintains a good long-term durability, which only declines 18% after 90 day operation. Coulombic efficiency (22.2%) obtained by Fe/FeO/FeS/NGC (900 °C) cathode is significantly higher than that of Pt/C (17.3%). Metallic state FeS anchored in porous NGC skeleton can boost electron transport through the interconnected channels in spongelike structure to improve catalytic activity. Charge delocalization of C atoms can be strengthened by N atoms incorporation into carbon skeleton, which correspondingly contributes to the O chemisorptions and O-O bond weakening during ORR. Energetically existed active components (Fe and N species) are more efficient than Pt to trap and consume electrons in catalyzing ORR in wastewater containing Pt-poisoning substances (bacterial metabolites). (Fe)/FeO/FeS/NGC catalysts with the advantages of durable power outputs and environmental-friendly raw material can cover the shortages of Pt/C and provide an outlook for further applications of these catalysts.

Graphene with Fe and S Coordinated Active Centers: An Active Competitor for the Fe–N–C Active Center for Oxygen Reduction Reaction in Acidic and Basic pH Conditions

“…Figure a–c show the deconvoluted Fe 2p spectra of P12-800, P12-900, and P12-1000. The Fe 2p 3/2 and Fe 2p 1/2 peaks of lower binding energy (709.70 eV) and higher binding energy (721.01 eV) are ascribed to the +2 oxidation state of Fe in the Fe–S bond. − On the other hand, the peaks appearing at binding energies of 711.96 eV and the 723.83 eV represent the +3 oxidation state of Fe. , Since iron sulfide exhibits high reactivity toward oxygen, it is expected that the reaction with the oxygen present in PEDOT and iron sulfide can lead to the formation of iron oxide during the pyrolysis process. All three samples display similar features in their Fe 2p spectral characteristics.…”

Durable and Efficient Hollow Porous Oxide Spinel Microspheres for Oxygen Reduction

“…[1][2][3][4][5] To this end, several low-cost non-noble-metal alternatives have emerged, including carbonbased materials, [6][7][8][9] non-precious transition metals and metal alloys (e.g., Fe, Co, Ni-Cu alloy), [10][11][12] and transition metal oxides (e.g., Fe 3 O 4 , Co 3 O 4 ). 13,14 However, transition metal oxides often possess high overpotentials. Moreover, carbon-based catalysts and transition metal alloys often involve poor durability, thus preventing them from large-scale commercial applications in PEM fuel cells and metal-air batteries.…”

Fe2O3 Nanoparticles Modified 2D N‐Doped Porous Graphene‐like Carbon as an Efficient and Robust Electrocatalyst for Oxygen Reduction Reaction

“…In Figure c, the C 1s peak can be fitted to C=C (284.8 eV), C=N&C–O (285.8 eV), C–N&C=O (287.1 eV) and O–C=O (289.6 eV), proving that the C atoms are combined with N and O atoms . As for the O 1s spectra (Figure d), three peaks observed at 530.2 eV, 531.2 eV and 532.7 eV, are assigned to Fe–O bond in Fe 2 O 3 , C=O, O‐C=O and physically absorbed O respectively …”