Catalysts Preparationand Its Electricity Generation Performancein Air-cathode Microbial Fuel Cell

Microbial fuel cell (MFC) is a new green energy technology. Using microbialmetabolism, MFC can convert chemical energy into electricity by oxidizing organicmatters and has great potential in wastewater treatment. Air-cathode MFC isconsidered as the most promising configuration to be scaled up, since it uses oxygenas electron acceptor directly. Air-cathode materials, especially the catalysts for oxygenreduction reaction (ORR), become one of the key factors for the application of MFC.Howerever, the application of MFCs in large scale is still limited by the high cost,complex preparation process and instability of the existing ORR catalysts. In thispaper, three types of cost-effcieent ORR catalyst were synthesized via simple processto facilitate the practical application of MFC in wastewater treatment. This thesisincluded the following three parts:(1) Plant-derived carbon catalyst was prepared by direct carbonazition of ricestraw and air-cathode was prepared by rolling methode. The electrochemicalperformance of air-cathode with plant-derived carbon as catalyst was comparaed tothat using carbon black as catalyst. The effect of binder dosage on the MFCperformance was evaluated based on plant-derived carbon catalyst. The resultsshowed that the plant-derived carbon had a better performance than carbon black. Thebinder dosage of catalyst layer had great influence on air-cathode performance. Thebest MFC performance with the highest voltage of0.558V and the maximum powerdensity of1058mW/m2was gained using air-cathode with catalyst/PTFE ratio of4.Maximum power density decreased to790mW/m2when the binder dosage increased.The avtive site of catalyst would be covered if too much binder. Howerver, thecatalyst layer cannot be tightly fixed if insufficient PTFE was used. The best binderdosage is the catalyst/PTFE ratio of4.(2) Phosphorus-doped (P-doped) carbon was prepared via direct pyrolysis ofcellulose phosphate. Air-cathodes were assembled by rolling method under theoptimized condition. Their performances in MFCs were studied and a series ofcharacterization of catalysts were carried out. The LSV rusults showed that theprepared catalyst can significantly improve the performance of air-cathode. Amaximum power density of1312mW/m2was produced by air-cathode MFC with P-doped carbon catalyst which was prepared at1000oC. This result was slightlyhigher than the air-cathode with Pt catalyst (1226mW/m2) and three times as thatwith P-free carbon catalyst derived from pure cellulose. The improved MFCperformance could be ascribed to the P doping in the carbon catalyst. This is the firsttime to prepare P-doped carbon through direct cabonazaion. With the advantages oflow cost and simple preparation process, the catalyst was a promising cathodiccatalyst for scale-up MFCs.(3) Nitrogen/phosphorus dual-doped carbon (PNC) was successfully synthesizedby a simple carbonization of cellulose in the presence of (NH4)3PO4. Air-cathodeMFCs were assembled by rolling method and their performances in MFCs werestudied. The LSV results showed that the PNC catalyst could improve theelectrochemical performance of air-cathode significantly. A hightest voltage output of0.636V and a maximum power density of2288mW/m2were produced by air-cathodeMFC with PNC-900catalyst. This result was higher than that with the commercial Ptcatalyst (1661mW/m2) and single doping catalyst (N, P). XPS results showed that Nand P were doped into the carbon. The improved MFC performance could be ascribedto the synergistic effects between the heteroatoms by N and P codoping.