Preparation Of Graphene Composite Cathode Material And Its Application In Microbial Fuel Cells

Microbial fuel cells (MFCs) utilize microorganisms as catalysts to decompose organic or inorganic matter and then harvest electricity, which represents a novel and promising technology for the generation of alternative power and wastewater treatment. The unique Power production method for MFC provides a new way to solve the energy problem and achieve the purpose of treating wastewater at the same time. At present, the poor electricity production performance as well as higher costs of MFC has become a major obstacle to limit its large-scale applications.As we know, the cost of the cathode catalyst occupies a large portion of the microbial fuel cell costs. Pt is the most common microbial fuel cell cathode catalyst, however, the cost of Pt is relatively high. To address this issue, grapheme/MnO2, porous nitrogen-doped carbon nanosheet and nitrogen-doped graphene which can be used as efficient and low-cost cathode catalyst have been prepared in this study. Meanwhile, nitrogen-doped graphene single-chamber air cathode microbial fuel cell has been successfully applied in p-nitrophenol(PNP) wastewater treatment. Some innovative findings in this study have been made as follows:Manganese dioxide-graphene nanosheet (MnO2/GNS) hybrid is used as an alternative cathode catalyst for oxygen reduction reaction (ORR) in air-cathode microbial fuel cell(MFC). The results show that the nano-structured MnO2/GNS composite exhibit an excellent catalytic activity for oxygen reduction reaction due to MnO2 nanoparticles closely anchored on the excellent conductive graphene nanosheets. As a result, MFC with MnO2/GNS as air cathode catalyst generates a maximum power density of 2083 mW/m , which is was 1.42 and 1.22 fold higher than those of pure MnO2 and Pt/C, respectively.Porous nitrogen-doped carbon nanosheet (PNCN) was prepared by a novel, low-cost,scalable synthetic method via the carbonization of graphite oxide-polyaniline hybrid(GO-PANI), subsequently followed by KOH activation treatment. Due to its high concentration of nitrogen and high specific surface area, PNCN exhibited an excellent catalytic activity for ORR. The maximum power density of 1159.34 mW/m2 obtained with PNCN catalyst in a MFC was 35% higher than that of Pt/C catalyst (858.49 mW/m2).Nitrogen-doped graphene can be prepared by the postprocessing using nitric acid or hydrazine hydrate a nitrogen source. Two types of nitrogen-doped graphene electrodes exhibited excellent catalytic performance for reduction of oxygen, and N-doped graphene prepared by nitric acid show a higher catalytic performance for ORR. The maximum power density obtained with two types of N-doped graphene catalyst in a MFC was higher than that of Pt/C catalyst.In this study, N-doped hraphene air-cathode single chamber MFC was built for the degradation of p-nitrophenol wastewater. MFC was operated by using mixed substrate and single substrate, respectively. The results show that MFC operated by using mixed substrate is more conducive to degrade the p-nitrophenol wastewater. When operated by using mixed substrate, the removal efficiency of p-nitrophenol decreases with increasing concentration, but still more than 70% which show that p-nitrophenol can be well removed by MFC. MFC operated by using mixed substrate which containing 50 mg/L p-nitrophenol generates a maximum power density of 561.69 mW/m2, the removal efficiency of p-nitrophenol is 77.35%, 20.27% higher than the ordinary anaerobic biological treatment.