Hydrogen peroxide generation in microbial fuel cells using graphene-based air-cathodes

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Science

Background:

• Bioelectrochemical systems (BES) offer novel methods for H₂O₂ generation via the oxygen reduction reaction (ORR).
• Cathode catalysts are crucial for optimizing ORR performance in BES.
• Understanding the role of functional groups on catalysts is key to improving H₂O₂ production.

Purpose of the Study:

• To investigate the catalytic performance of plain graphene, oxidized graphene, and graphene oxide (GO) for H₂O₂ generation in microbial fuel cells (MFCs).
• To elucidate the influence of oxygen-containing functional groups on ORR activity and H₂O₂ yield.
• To assess the potential of oxidized graphene as a cathode catalyst for simultaneous wastewater treatment, power generation, and H₂O₂ production in MFCs.

Main Methods:

• Fabrication and characterization of plain graphene, oxidized graphene, and GO air-cathodes.
• Electrochemical performance evaluation in abiotic reactors and MFCs.
• X-ray photoelectron spectroscopy (XPS) analysis to determine surface chemistry and functional groups.

Main Results:

• Oxidized graphene air-cathodes demonstrated significantly higher H₂O₂ production compared to plain graphene cathodes (78% in abiotic, 131% in MFC).
• Graphene oxide (GO) exhibited minimal H₂O₂ production.
• XPS analysis revealed a 5.7% oxygen atomic fraction in oxidized graphene, primarily in the form of C-O-C bonds, correlating with enhanced catalytic activity.

Conclusions:

• Oxidized graphene possesses excellent catalytic properties for H₂O₂ production through ORR in BES.
• Oxygen-containing functional groups, particularly C-O-C, significantly enhance catalytic performance, while overoxidation has adverse effects.
• Oxidized graphene cathodes enable simultaneous wastewater treatment, energy generation, and H₂O₂ production in MFCs, highlighting their multifunctional potential.