Preparation And Characterization Of Carbon Supported Spinel Oxides And Its Application In Microbial Fuel Cells

As a novel energy technology, microbial fuel cell (MFC) with facile operation condition and environmental friendly can utilize microorganisms to degrade certain castoff and produce electricity. The technology can provide a solution direction of energy and environment problems and has become an advanced research hotpot in some fields.MFC have broad prospect in the future because of its potential advantages. However, large scale application of MFC still remains impractical. The low power density output can not meet practical use demand, which is the main obstacle that limits the commercialization of MFC. The efficiency of oxygen reduction reaction (ORR) is one primary factor that influences the power density output. In particular, both the high overpotential and sluggish kinetics of ORR lower its efficiency. Therefore, choosing appropriate cathodic catalyst is of great significance in terms of improving ORR performance. In this study, nanocarbon materials supported by spinel oxides were prepared, characterized and used as cathodic ORR catalysts to investigate the power output performance of MFC.Firstly, spinel metal-oxide (m-MnCo2O4) with small partical size, large specific surface area and uniform dispersion was prepared through ammonia vapouration induced synthetic method. SEM, XRD and BET show that m-MnCo2O4 possesses samller partical size (60nm) and larger specific surface area (133 m2/g) compared with b-MnCo2O4 prepared by hydrothermal method. Mixturing the catalysts with certain XC-72 uniformly to investigate the ORR performance and the results indicate that the reduction peak potential is more positive than that of b-MnCo2O4, the current density and onset potential are slightly poor than that of Pt/C. The electron transferred number of m-MnCo2O4 is calculated to be 3.77, which suggests that m-MnCo2O4 favors a 4 e- ORR path, improving the efficiency of ORR activity.Then, nitrogen doped carbon nanotube supported by manganese cobalt spinel oxide (MnCo2O4/N-CNT) was synthesized through hydrothermal method. The morphology of MnCo2O4/N-CNT and the electrocatalytic activity of MnCo2O4+N-CNT, Co3O4/N-CNT, MnCo2O4, and MnCo2O4/N-CNT were investigated. TEM shows that hydrothermal method can disperse MnCo2O4 nanoparticals on the surface of CNT uniformly and enhance the chemical coupling effect of MnCo2O4 and N-CNT. ORR results show that MnCo2O4/N-CNT possesses relatively higher stability and superior poison resistance.Furthermore, MnCo2O4/N, S-CNT composite was successfully synthesized through a novel thermal-coprecipitation method. CV performance of samples with different CNT mass ratios and the ORR catalytic activity of CNT, N,S-CNT, MnCo2O4/CNT and MnCo2O4/N,S-CNT were investigated. The results show that the sample with 40 wt% CNT has optimum CV performance and the ORR electrocatalytic activity of MnCo2O4/N,S-CNT is superior to that of MnCo2O4/CNT.Finally, MnCo2O4/N-CNT, MnCo2O4/N,S-CNT and Pt/C composites were used as cathodic catalysts to study the electricity produce performance of MFC, respectively. The polarization curves indicate that the open circuit voltage and maximum power density of MnCo2O4/N-CNT and MnCo2O4/N,S-CNT are 0.714 V,673 mW/m2 and 0.705 V,767 mW/m2, respectively, which are both far higher than that of plain cathode MFC(0.489 V,186 mW/m2), but slightly inferior to Pt/C(0.747 V,864 mW/m2).In this paper, we prepared different nanocarbon supported spinel metal oxides through different methods and investigated the influence factors of ORR electrocatalytic activity. It is found that the synthetic methods, the chemical coupling effect, the loading of CNT, metal ion doping in spinel and N, S doping in CNT have significant influence on ORR catalytic activity. And we also found that nanocarbon supported spinel metal oxides used as cathodic catalysts can enhance electricity-produce performance.