WC And Ti₃C₂ As Excellent Anode Materials For High-performance Microbial Fuel Cells

Microbial fuel cell?MFC?is a device that converts chemical energy into electricity by catalytic decomposition of organic matters in anolyte with microorganisms.Its main application prospect is to generat clean energy while wastewater treatment,which can not only significantly reduce the energy consumption in wastewater treatment,but also recycle some energy.However,the performance of MFC can not meet the actual application requirements.In addition,a large number of studies have shown that the anode is the main factor that restricts the performance of MFC,which can affect the adhesion of microorganisms on the surface of the electrode,and the efficiency of electron transfer.At present,some commonly used anode materials,including carbon-based materials,composite materials and metal-based materials,etc.,which have the disadvantages of high charge transfer resistance,high cost,low hydrophilicity and poor stability,which limit the further performance of MFC.In this paper,a carbon cloth coated with tungsten carbide?WC?nanoparticles with excellent electrocatalytic activity was used as the MFC anode,achieved a long output voltage period of 6-7 d,and the highest power density of 3.257 W/m²,which is 2.15times that of CC anode.The 81.7%of microorganisms on the WC/CC anode biofilm are Geobacter,Geothrix and Pseudomonas,which exhibited a high coulombic efficiency of83.2%in the MFC.Based on Ti₃C₂ MXenes,it has excellent conductivity and a stack of accordion-like structures,which can accelerate the mass transfer in the anolyte and is expected to achieve higher power density output than WC anodes.Therefore,Ti₃C₂MXenes was employed as the MFC anode for the first time.As expected,the MFC with Ti₃C₂ MXenes anode achieved the highest power density of 3.74 W/m²,start-up quickly and exhibited high voltage output of 0.645 V?external resistance is 1000??.The biofilm species on the surface of the Ti₃C₂ MXenes anode is very rich,which is twice the surface of the CC anode as control.The combination of Geobacter and other unknown electricigens lead to high efficiency of power output.In addition,Lentimicrobium also plays an important role in promoting extracellular electron transfer.Cytochromes and nanowires together facilitate extracellular electron transfer on the surface of WC and Ti₃C₂ MXenes anodes.The above high-performance MFCs based on WC and Ti₃C₂ MXenes anodes are attributed to their efficient enrichment of electricigens and the ability to catalyze the decomposition of organic matters and increase the efficiency of extracellular electron transfer.