Cu-based Oxidation-reduction Catalysts And Their Properties In Microbial Fuel Cells

Energy crisis and environmental pollution make people realize the importance of developing green,efficient and sustainable clean energy.The microbial fuel cell（MFC）is a new sustainable bio-energy technology that can recover electric energy from sewage treatment.It has attracted much attention and has a promising future due to its advantages of mild operating conditions and environmentally friendly.Cathode oxygen reduction reaction（ORR）is one of the key factors affecting the performance of the MFC.Therefore,it is of great hotspot to develop efficient,stable and low-cost cathode catalysts for the MFC.In recent years,copper-based catalysts with simple ligand,low toxicity and low price have been considered as promising ORR catalysts.Defect construction,morphology regulation,co-doping,and recombination with quantum dots are common and effective strategies for improving catalytic activity of catalysts,as they can enhance the conductivity and the ability of oxygen and protons transfer,thus improving the activity and stability of ORR.In this study,V-Cu₃₆Ni_xPt₄₅and N,S-CQDs/Cu₂O-Cu NWs with copper defects were prepared as cathode ORR catalysts.The structure-activity relationship of the catalysts was determined by a series of physicochemical and ORR electrochemical characterizations.Furthermore,it was adopted in the MFC as the cathode,and its performance,long-term operation stability and practical application potential were evaluated.The main results are as follows:（1）With the nickel foam as the supporting material,the three-dimensional（3D）flower-like Cu₃₆Ni_xPt₄₅nanospheres with Cu defects growing on Ni（OH）₂nanosheets were rational designed through a simple hydrothermal synthesis method.Results indicated that the optimized material possessed more Cu defects,which was beneficial to exposing more active sites for ORR kinetics.In ORR process,C=O bond could act as an ORR active species to promote the balance between desorption and adsorption.The excellent ORR activity was due to its unique morphology,abundant Cu defects and C=O bond active substances,which promoted electron transfer and improved electrical conductivity.In the MFC,the maximum power density of the V-Cu₃₆Ni_xPt₄₅(1682.8±40.9 m W·m^-2)was 2.56 times of that of the Pt/C(658.0±41.7 m W·m^-2),while the output voltages could remain stable within 50 d of operation,also outperformed the Pt/C.（2）Based on the abundant functional groups,excellent performance and environmental protection performance of biomass derived carbon quantum dots（CQDs）,orange-peels-derived N,S co-doped carbon quantum dots（N,S-CQDs）were in-situ anchored on copper-vacancy-rich Cu nanowires/Cu foam（V-Cu NWs/CF）（copper foam as the supporting material）by hydrothermal method,obtaining the N,S-CQDs/Cu₂O-Cu NWs,which was used to catalyze ORR in MFCs.Owing to the C-S-Cu bond bridge between N,S-CQDs and V-Cu NWs/CF,the electrode/electrolyte transfer interface of N,S-CQDs/Cu₂O-Cu NWs was optimized,the charge transfer resistance was reduced,and catalytic active sites were abundant,all together endowing N,S-CQDs/Cu₂O-Cu NWs excellent ORR activity,better than that of Pt/C catalyst.In MFCs,the maximum power density(924.5±32.5 m W·m^-2)of N,S-CQDs/Cu₂O-Cu NWs was 1.34times that of Pt/C(686.5±28.0 m W·m^-2),and its long-term stability of output voltage within 30 d also outperformed the Pt/C.