BACKGROUND: Hydrogen peroxide (H 2 O 2 ) is an important chemical product, and this study investigated its synthesis at the cathode of a microbial fuel cell (MFC) system using spectrographically pure graphite (SPG) rods as cathode electrode.

several limiting factors can weigh heavily against the overall performance before the MFC technology can gain a signifi cant share of energy market. In particular, the power generated from MFC is commonly limited by the cathode poor performance owing to kinetic sluggishness of cathodic oxygen reduction reaction (ORR) in pHneutral aqueous electrolyte. [ 2 ] The ORR takes place through twoelectron (H 2 O 2 ) or four-electron (H 2 O) pathway depending on the electrocatalyst and electrolyte used. To maximize power density and energy conversion of MFC, the four-electron ORR process is necessary. This gives priority to explore highly active electrocatalyst toward four-electron ORR under pH-neutral condition. [ 2b , 3 ] Much effort has been devoted to enhance the cathode performance by either exploring available electrocatalyst, such as noble metals, nitrogen-doped carbonaceous materials and transition metal or metal oxides, or optimizing the property of three-phase boundary where oxygen reacts with electron and proton to form water. [ 4 ] However, there still exist several challenges for the carbonsupported particle-structured electrocatalysts in MFC, due to the occurrence of migration and agglomeration of catalyst particles at "water-fl ooding" three-phase boundary. [ 2b ] Inevitably, this will cause the loss of electrochemically active surface area for mass transfer of protons and oxygen, and thus the decrease in the activity, selectivity, and stability of the electrocatalyst. [ 5 ] Meanwhile, despite the best performance of platinum catalyst observed hitherto, the high cost and scarcity of platinum constitute the obstacle in the drive for scale-up applications. [ 2b , 6 ] Therefore, developing an inexpensive electrocatalyst with nonparticulate defi ned 3D porous structure, large surface area, and abundant active sites for effi cient cathodic oxygen reduction in MFC is still highly desirable.Metal-organic frameworks (MOFs), which consist of metal ions (clusters) and organic ligands, have a highly defi ned 3D network structure at molecular level. [ 7 ] Given their unique properties of high surface area, tunable porous structures, and uniform open cavities, [ 8 ] MOFs have attracted growing interest in potential applications in many areas, such as gas storage and Microbial fuel cell (MFC) can generate electricity from organic substances based on anodic electrochemically active microorganisms and cathodic oxygen reduction reaction (ORR), thus exhibiting promising potential for harvesting electric energy from organic wastewater. The ORR performance is crucial to both power production effi ciency and overall cost of MFC. A new type of metal-organic-framework-derived electrocatalysts containing cobalt and nitrogen-doped carbon (CoNC) is developed, which is effective to enhance activity, selectivity, and stability toward four-electron ORR in pH-neutral electrolyte. When glucose is used as the substrate, the maximum power density of 1665 mW m −2 is achieved for the optimized CoNC pyrolyzed at 900 °C, which is 39.8...

The oxygen-buffering CeO2 effectively protects the available active sites of the ZIF-67-derived Co3O4@carbon to improve oxygen reduction/evolution reaction activities.

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