Improvement On The Electricity Generation Performance Of G.sulfurreducens By Stainless Steel Fiber Felt And Carbon Nanotubes

Recently,the researches on microbial fuel cell（MFC）are getting more extensive and intensive.However,while the output power density is relatively low and the cost of the constructive material（especially the anode material）is not cost-effective,the large-scale application of MFC is terribly hindered.As macroporous electrodes offer more adhesion sites and more reaction area for exoelectrogen,macroporous electrodes can improve the power output of the MFC to a great extent.However,the studies on the effects of the mean pore sizes of the macroporous to the electrochemical performance of the electrochemically active biofilms（EABs）remain rare.Compared to the traditional carbon-based electrode,stainless steel electrode is cheaper,more conductive and ductile.3D stainless steel material owns less resistance and more mechanical strength.Therefore,this study chose stainless steel fiber felts（SSFFs）as the object and investigated the relationship between the mean pore size of the macroporous anode and the bioelectrocatalytic performance of EABs on it.Herein,graphite plate（GP）and SSFFs with mean pore sizes of 15μm,100μm and 150μm（SSFF15,SSFF100 and SSFF150）were investigated as working electrodes in the three-electrode system with a pure culture of the model organism Geobacter sulfurreducens.As a result,the maximum current densities of G.sulfurreducens on SSFF15,SSFF100,SSFF150 and GP electrode was151298±185μA·cm^-2,which were 1298.83±185.01μA·cm^-2,577.36±61.79μA·cm^-2,527.22±50.95μA·cm^-2 and 624.37±52.13μA·cm^-2.It is obvious that,the electrochemical performance of G.sulfurreducens on SSFF15 was the best,and the maximum current density of it was 2.24,2.46 and 2.08 times of the SSFF100,SSFF150 and GP electrode,respectively.In addition,to compensate the poor biocompatibility and further enlarge the specific surface area of SSFFs,they were modified with carbon nanotubes（CNTs）and assembled in three-electrode system as working electrode.The results showed that after CNTs modification the EABs on the SSFFCNTs electrode were thicker at various levels,which indicates that the CNTs modification did improve the biocompatibility of the SSFF electrode.What’s more,the maximum output current densities of SSFF15CNTs,SSFF100CNTs and SSFF150CNTs were 1984.37±286.31μA·cm^-2,1396.62±104.08μA·cm^-2 and 924.31±44.95μA·cm^-2,which was 3.18,2.23 and 1.48 times of the maximum current density on GP electrode.Compared to SSFF15,SSFF100 and SSFF150,CNTs modification improved the current genenration ability of G.sulfurreducens by 49.8%,149.7%and 84.2%.According to the results of electrochemical impedance spectra（EIS）,the charge transfer resistances of the system were far more less after CNTs modification.In the meantime,according to the Tafel curves,the CNTs modification also improved the anti-corrosion performance of the SSFF electrode.It was found that the performance of G.sulfurreducens on SSFF15 was the best among SFF15,SSFF100,SSFF150 and GP electrodes.The CNT_S modification can improve the bioelectrocatalytic performance of the G.sulfurreducens to a great extent.The observed variations in bioelectrocatalytic performances before and after CNTs modifications were well supported by morphological and electrochemical characterization.The results of this study offer a practical reference for optimization of the pore size for macroporous material as anode in MFC and a theoretical guidance of the application of stainless steel anode.