Preparation And Oxygen Reduction Performance Of Co-based Cathode Catalyst For Microbial Fuel Cells

Microbial fuel cell（MFC）is a new type of environmental protection device which converts soluble organic matter into electric energy using microorganism as biocatalyst.However,the low efficiency of cathode oxygen reduction（ORR）results in low power density of MICROBIAL fuel cells,which limits its practical application.Precious metals,such as platinum and platinum-based catalysts,are effective catalysts for ORR.However,the scarcity and stability of these precious metals are poor,and their large-scale application is limited.Therefore,non-noble metal ORR catalysts are the focus of research.In this paper,the catalysts Co₃O₄-ZIF/Zn-T-X（T is calcination temperature,^oC）and Co₃O₄-ZIF/Zn-Mn O₂-X（X represents the added mass of potassium manganese）were prepared using leaf structure metal-organic framework as template and cheap transition metals Co,Zn and Mn as active components.The catalysts were characterized by XRD,XPS,BET,TEM,TG and SEM,and electrochemical tests were carried out by CV,LSV and EIS.In single-chamber MFC,the effects of roasting temperature,Co addition amount and potassium permanganate addition amount on the performance of microbial fuel cells were studied,and the results are as follows:（1）The ORR catalyst of Co₃O₄-ZIF/Zn-T-X microbial fuel cell was prepared using Co-ZIF/Zn-67 template with bimetal blade structure.Among the Co₃O₄-ZIF/Zn-T-3 catalysts,the Co₃O₄-ZIF/Zn-400-3 catalysts roasted at 400 ^oC showed the best ORR performance,with an initial potential of 0.082 V and a power density of 656.9 m W/m².The ORR activity was close to that of the commercial Pt/C catalyst,while its stability was much better than that of the commercial Pt/C catalyst.（2）Co₃O₄-ZIF/Zn-400-2 catalyst has the highest content of pyridine nitrogen,abundant N-C active sites and more uniformly dispersed active Co₃O₄ particles,and has the best ORR performance.Its highest output voltage is 0.52 V.Equivalent to the output voltage of commercial Pt/C（0.58V）.（3）Co₃O₄-ZIF/Zn-Mn O₂-X catalyst was prepared by loading Mn O₂ on Co₃O₄-ZIF/Zn-400-2.It is found that Co and Zn exist in the form of Co₃O₄ and Zn O,respectively,and Mn exists in the form ofα-Mn O₂.（4）Among the Co₃O₄-ZIF/Zn-Mn O₂-X catalysts,The ORR activity of Co₃O₄-ZIF/Zn-Mn O₂-2 was the best,and the output voltage of Co₃O₄-ZIF/Zn-Mn O₂-2catalyst was 0.09 V higher than that of Co₃O₄-ZIF/Zn-400-2 catalyst without Mn O₂（0.52 V）.（5）The initial potential of Co₃O₄-ZIF/Zn-Mn O₂-2 is 0.12V,which is close to the initial potential of commercial Pt/C（0.14V）,and the limiting current density is-6.97 m A/cm²,which is significantly higher than that of commercial Pt/C（-5.31 m A/cm²）.The internal resistance of charge transfer is8.7?,less than Pt/C（11.7?）.When applied to MFC,the maximum power density of the catalyst is883.3 m W/m²,which is better than that of the commercial Pt/C catalyst（848.1 m W/m²）.