Fe-Co Metal-organic Framework Derivatives Oxygen Reduction Catalysts And Their Properties In Microbial Fuel Cells

Energy shortage and environmental pollution are becoming increasingly serious.It is urgent to research and develop green and efficient energy storage and conversion technology.The microbial fuel cell（MFC）is a new sustainable bioenergy technology that can simultaneously treat wastewater and generate electricity.It is environmentally friendly and has broad application prospects.However,the sluggish kinetics of cathodic oxygen reduction reaction（ORR）is one of the main factors hindering large-scale application of MFC.Therefore,it is of great significance to develop efficient,stable and low-cost cathode catalysts for MFC.Metal-organic Framework（MOF）has attracted wide publicity in the field of electrocatalysis because of its large specific surface area,tunable pore size and high design feasibility.In this study,Fe Co-bimetallic organic framework grown in situ on nickel foam was prepared,and Fe_xCo_3-xS₄/Fe_yCo_9-yS₈ and BGQDs/MOF-t were developed as ORR catalysts cathodes.The physical properties and electrochemical properties of the materials were characterized,and the micro morphology,electron transfer and active sites,were analyzed to explore the synergistic effect of co-doping or quantum dots with MOF.Furthermore,it was applied as the cathode of the MFC and compared with Pt/C electrode in terms of evaluating its performance,long-term operation stability and practical application potential.The main results are as follows:（1）The MOF-derived Fe_xCo_3-xS₄/Fe_yCo_9-yS₈（Fe Co S（MOF））was in-situ grown on nickel foam as ORR catalyst with high dopings of N and S by hydrothermal method.Results showed that based on the role of Fe Co MOF,the Fe Co S（MOF）microspheres were made up of nanosheets piling-up.Meanwhile,more defects were generated,resulting in low internal resistance,high quality activity and high turnover frequency.In the MFC with the Fe Co S（MOF）cathode,the maximum power density was 2.55 times of that of Pt/C cathode.The excellent ORR activity was attributed to the unique morphology and rich oxygen defects,which shortened electronic transmission distance,facilitated the exposure of more active sites,and improved oxygen adsorption and conductivity.Moreover,the durability of Fe Co S（MOF）cathode outperformed Pt/C cathode,with stable output voltage maintained for 2 months,while the Pt/C cathode decreased to 67%of the initial voltage.（2）The B-doped graphene quantum dots implanted into bimetallic organic framework（BGQDs/MOF-t）were fabricated by a facile electro-deposition.Result showed that,the direct in-situ growth of Fe Co MOF on nickel foam could effectively assist construction of nanoflowers with compact connections,thus improving the conductivity.More importantly,this nano-network could serve as the template for the implantation of BGQDs through powerful interface M-O-C bonding,avoidingÏ€-Ï€rearrangement and providing efficient charge transfer and abundant edge active sites.Benefitting from the enhanced electrode/electrolyte transport interface,abundant catalytic sites and low charge transfer resistance,the BGQDs/MOF-15 exhibited excellent ORR activity,superior to commercial Pt/C catalyst.In the MFC with the BGQDs/MOF-15 cathode,the maximum power density enhanced 53%as compared with the Pt/C cathode.In addition,the BGQDs/MOF-15 cathode maintained great stability over 800 h,also outperformed the Pt/C cathode.