Study On Cathodic Properties Of Modified Ceria/Carbon-Based Microbial Fuel Cells

Since the rapid development of economics,increased demand of energy,it is urgent to develop the renewable energy sources.Microbial fuel cells have drawn much attention due to their ability to convert the organic wastes into electric energy by the metabolism of electricigens.However,there are some limitations in microbial fuel cells such as difficulty in obtaining higher output voltage and higher cost of cathode catalyst that hindering their large-scale and commercial application.The article starts from the point of view of reducing the cost of cathode catalysts and improving the catalytic activity of the catalysts to improve the electrical generation performance of microbial fuel cells by modifying the ceric dioxide and introducing different carbon substrates.The detailed information about the chemical component and structure of the as-prepared catalyst is analyzed by the characterization techniques such as XPS,BET,SEM and TEM.The cyclic voltammetry?CV?and linear sweep voltammetry?LSV?is performed to further evaluated their electronic activity.Furthermore,the electron transfer number?n?was calculated by using the Koutecky-Levich equation in the RDE tests.In this study,we synthesis a graphite substrate supported the active component of CeO₂-CuO composites?CeO₂-CuO/EG?by using the solvent-free method and use expanded graphite,urea cerium nitrate and copper sulfate as carbon source,cerium source and copper source,respectively.In CeO₂-CuO,ceria has excellent oxygen storage capacity oxygen storage capacity,which can guarantee the oxygen concentration supplied on cathode surface,and the presence of copper oxide can promote more active sites to be exposed.Furthermore,the graphite material has good conductivity,which can improve the electron transport efficiency.The CeO₂-CuO/EG composite shows a large current density in the CV and LSV tests,indicating its excellent ORR catalytic activity.During continuous operation of 1700 h,the highest output power density of microbial fuel cells is obtained by the CeO₂-CuO/EG cathode(992.6 mW m^-2),which is higher than that of commercial Pt/C.In order to improve the output power of microbial fuel cell,ceria is further modified.A new type of nitrogen,sulfur co-doped Ce-species supported by carbon matrix is prepared by a one-step in-situ reduction method using pomelo skin,thiourea and cerium nitrate as carbon sources,sulfur sources,nitrogen sources and cerium sources,respectively.The excellent oxygen reduction activity of catalysts can be ascribed to the synergistic effect between the well-ordered mesoporous structure and the abundant active sites.Ce₂O₂S/NSC-950 is exploited as the MFC cathode catalyst and the maximum power density of Ce₂O₂S/NSC-950 is 1087.20 mW m^-2,which is better than that of commercial Pt/C(989.31 mW m^-2).After 80 days operation,the deterioration of the power density of Ce₂O₂S/NSC-950 is 8.7%,which is lower than that of Pt/C?36.7%?,showing better durability and long-term operating stability.More importantly,the Ce-species/NSCs with high ORR catalytic activity and remarkable operation durability may pave a new avenue to further develop the application of the cathode of MFCs.