Preparation And Application Of Anti-biological Fouling Cathode Catalysts For Microbial Fuel Cell

Microbial fuel cell（MFC）is a kind of green energy technology with the advantages of wastewater treatment and electricity generation,which can directly convert chemical energy from sewage into undefiled electricity with the help of the electroactive bacteria feeding on organic pollutants in wastewater.However,the tardy kinetics of the cathodic oxygen reduction reaction（ORR）and the propagation of aerobic bacteria easily adhered to the air-cathode consuming a good deal of available oxygen and competing against the ORR,greatly reduce the output voltage and power density of the MFC and thus limit its wide practical application.To solve the scientific problems of slow cathode ORR kinetics and biofilm contamination,in this paper,a series of cathode catalysts with both antibacterial activity and ORR catalytic activity were created by the means of introducing antibacterial active species into the transition metal-nitrogen-carbon（M-N-C）catalysts and combining with the strategies of secondary metal doping and chalcogen doping,and realized the improvement of MFC power production capacity and stability.The details are as follows:（1）The zeolitic imidazole framework（ZIF）-derived Ag-Fe-N/C catalysts with good electrocatalytic activity were developed by a synthetic strategy of chemisorption,calcination,and photo-deposition,using the ZIF-8 as precursor.The optimal Ag-Fe-N/C-2 catalyst had a half-wave potential(E_1/2)of 0.87 V vs.RHE in 0.1 M KOH and 0.75 V vs.RHE in 50 m M PBS solution,both higher than that of commercial Pt/C.The single-chamber air-cathode MFCs assembled with it as the cathode catalyst exhibited outstanding long-term stability and power generation with the maximum power density（MPD）of 523±7 m W m^-2 and the output voltage（OV）of 568±7 m V.In addition,the introduction of Ag NPs endowed Ag-Fe-N/C-2 catalyst with great antibacterial ability,which affected the microbial community structure on the cathode biofilm and was able to inhibit the propagation of aerobic bacteria without influencing the electricity generation of the electrochemically active bacteria,which was beneficial to the constant output of stable voltage of MFCs.（2）Cu-N/C@Cu composites were synthesized as bifunctional cathode catalysts for MFC by doping,adsorption,and two calcinations by using Cu-ZIF-8 as the precursor.The higher Cu-N_xcontent confered remarkable ORR catalytic activity to the optimized Cu-N/C@Cu-2 catalyst with the E_1/2 of 0.67 V vs.RHE in a neutral solution,which was on the verge of commercial20%Pt/C（0.70 V vs.RHE）.The MPD of the MFCs assembled with Cu-N/C@Cu-2 reached581±13 m W m^-2,which was superior to Pt/C(499±13 m W m^-2).Besides,the results of antimicrobial activity and biomass test displayed that Cu-N/C@Cu-2 with the higher Cu content resulted in better against the contamination ability of cathode biofilm.And the 16S r DNA results revealed that the community structure of the biofilm was favorable for the power production and purification of MFCs,suggesting that copper-based materials could be used as potential bifunctional catalysts to accelerate the application of MFC in wastewater treatment.（3）A series of chalcogen-doped bifunctional catalysts Cu₂X@Cu-XNC-x（X=S or Se,x=1,2 and 3）were obtained successfully via the method of high-temperature carbonization followed by sulfuration or selenylation.Among the catalysts,the optimized Cu₂S@Cu-SNC-2 catalyst displayed the splendid durability and ORR activity with 0.73 V vs.RHE in E1/2,significantly excelling the commercial 20%Pt/C（0.70 V vs.RHE）in neutral solution.Moreover,the MPD of Cu₂S@Cu-SNC-2-based MFC reached up to 904±25 m W m^-2,comparing with the commercial 20%Pt/C(477±22 m W m^-2),and possessed less cathode biofilm after long-term operation.The results indicated that the proper doping of chalcogen（such as S and Se）could maintain antimicrobial activity while effectively improving ORR performance,which was conducive to efficient and stable operation of MFCs.