Performance Optimization For Binuclear-cobalt-phthalocyanine As Cathode Catalyst In Single Chamber Microbial Fuel Cells

Microbial fuel cell(MFC), a novel electrobiochemical system capable of converting organic contaminants to electricity, has drawn intensive attention in the past decade. MFC plays an important role in the energy shortage in the 21 st century. In cathode, oxygen in air has been widely used as the electron acceptor in single chamber MFCs(SCMFCs), due to its accessibility in environment and clean product. However, the oxygen reduction reaction(ORR) on cathodes requires efficient catalysts to overcome the high overpotential. Therefore, cost-effective catalysts have been developed to replace Pt in MFCs.Carbon cloth loaded Bi-Co Pc/C as a novel cathode catalysts was investigated in this study. The effects of substrate sodium acetate concentration, ionic strength and p H value of the solution were optimized. The MFCs reached the maximum output capacity with loading 1 mg/cm2 of catalysts, 2 g/L of sodium acetate concentration, 100 m M of sodium chloride concentration, and p H value of 6.Furthermore, a novel hybrid binuclear-cobalt-phthalocyanine(Bi-Co Pc) is developed as the cathode catalyst to replace the costly platinum(Pt) in single chamber microbial fuel cells(SCMFCs). Bi-Co Pc/C was integrated withmetal oxides(N i O and Co O) to form macrocyclic complex for enhanced oxygen reduction rate(ORR). The characteristics of hybrid catalysts(Bi-Co Pc/C-Co O and Bi-Co Pc/C-Ni O) were compared with Co-contained catalysts(Co Pc/C and Bi-Co Pc/C) and metal oxide catalysts(N i O and Co O). The surface morphological property was examined using TEM and XPS. The increase in O and N functional groups indicated the benefits of Ni O and Co O to the cathode catalysts. The cyclic voltammetry(CV) shows the reduction peak for Bi-Co Pc/C-Ni O and Bi-Co Pc/C-Co O at-0.12 V and-0.22 V, respectively. The power densities(368 m W/m2 and 400 m W/m2) of SCMFCs with Bi-Co Pc/C-Co O and Bi-Co Pc-Ni O/C are the highest among the cathodes tested, and close to that of Pt(450 m W/m2). This study demonstrates that hybrid Bi-Co Pc/C with metal oxides has a great potential as a cost-effective catalyst in MFCs.A novel Pt- free cathodic material binuclear-cobalt-phthalocyanine(Bi-Co Pc) pyrolyzed at different temperatures(300-1000 oC) was examined as oxygen reduction reaction(ORR) catalyst, and compared in performance to Pt and unpyrolyzed Bi-Co Pc/C in SCMFCs. The products were characterized by SEM, TEM, XPS and XRD respectively. The electrocatalytic activities of Bi-Co Pc/C-(T) were examined using cyclic voltammetry(CV) and linear sweep voltammetry(LSV). The pyrolysis process increased the amounts of nitrogen on the surface and changed the nitrogen species. The XPS results showed that the high-temperature pyrolysis at 800 oC contained a significant amount of the pyrrolic-N configuration. The high electrochemical catalytic activity of the Bi-Co Pc/C-800 catalyst indicated the dominating role of pyrrolic-N. The power densities and current densities increased over time with higher values generated by the heated catalysts following the order: Bi-Co Pc/C-800 > Bi-Co Pc/C-1000 > Bi-Co Pc/C-600 > Bi-Co Pc/C-300 > Bi-Co Pc/C. SCMFC with Bi-Co Pc/C-800 cathode produces a maximum power density of 604 m W/m2, only17% less than cathode with Pt/C(724 m W/m2). The excellent electro-catalytic activity for Bi-Co Pc/C-800 shows the great potential to replace the costly Pt catalyst and Bi-Co Pc/C cathode is more feasible in MFC field scale application.