Preparation And Application Of Multifunctional Carbon-based Electrode Materials Based On Sewage Sludge

Microbial fuel cells(MFCs)have attracted increasing interest as a component of sustainable electricity generation and wastewater treatment processes,due to their ability to extract energy from contaminants using bacteria as catalysts.However,scaling MFC for commercial application is still limited by the low power density and high cost.An ideal anode must be highly biocompatible and should readily generate electrons,as well as being inexpensive and durable.In addition,it is important to seek for efficient,cost-effective and eco-friendly ORR electrocatalysts for fuel cell cathode construction.By taking excess sludge as the precursor material of carbon materials,the paper employed a simple and easy method to prepare low-cost,high performance sludge-based electrode and sludge-based composite air cathode.It consequently enables the power output of MFC to reach a higher level while reducing the cost of electrode,and lays the foundation for the application of MFC in the field of wastewater treatment.(1)By taking excess sludge as the unique precursor material of electrode materials,the paper adopted the method of direct carbonization with the protection of nitrogen to produce the sludge-based electrode and investigated the influences being exerted by the carbonization temperature on electricity generation performance of electrode.According to experimental results,the increase of carbonization temperature contributes to the improvement of electricity generation performance of electrode.When the carbonization temperature is 1200?,the sludge-based electrode will reach the highest degree of graphitization,the surface area of electrode will be the maximum,the ratio of carbon content in electrode and the electric conductivity of electrode will reach the top.When the MFC is operated with carbonized sludge-based anode electrodes under the temperature of 1200?(SSC1200),its maximum output power will be 2920 mW m-2,that is,2.5,1.3,1.2 and 5 times the output power density of SSC600,SSC800,SSC1000 and commercial graphite electrode respectively.Hence,the optimal carbonization temperature for sludge-based electrode is 1200?.(2)Based on the optimal sludge-based carbonation conditions(1200?),the industrial waste fly ash binder was mixed into the sludge-based electrode at a ratio of 20%,40%,60%and 80%to enhance the performance of the electrode.Onion-like carbon was observed at the ends of the carbon wires on the surface of SSFA20,which is conducive to electron transfer and improve the electricity generation performance of electrodes.The mix of fly ashes in sludge-based electrodes can significantly enhance the hydrophilia of electrodes and contribute to the apposition growth of electricigens.Moreover,after mixing sludge-based electrodes with fly ashes,the mechanical strength is improved by about 20 times.The maximum power density of 3210 mW m-2 is achieved using the electrode with 20%fly ash,which is 20%higher than that of the electrode without fly ash.These results demonstrated that the electrodes provided by direct carbonization of SS mixed with fly ash are promising as high-performance MFC anodes.(3)In this paper,we use sewage sludge as carbon precursor,successfully prepared a new sludge carbon-based air cathode by hydrothermal co-doping Mn,N method.EDS and XPS results showed that Mn and N atoms were successfully and evenly mingled in the carbon skeleton,which is beneficial to improve its ORR catalytic performance.The MFC with the Mn-N/SC catalyst cathode had a power density of 1120 mW m-2,which was only slightly lower than that of the MFC with the Pt/C cathode catalyst(1240 mW m-2).The power density result revealed that Mn-N/SC was a promising catalyst for MFC to replace commercial expensive Pt/C catalyst.