Preparation And Antibacterial Pollution Of Cathodic Catalysts Derived From Copper-based Metal-organic Frameworks

The increasingly severe energy shortage and environmental pollution have prompted people to explore green and renewable energy to maintain sustainable development of human society.Microbial Fuel Cell（MFC）can use microorganisms to degrade organics and produce bioelectric,which are regarded as green energy conversion technology without secondary pollution.According to the final available electron acceptor,the cathodic reduction of MFC can be divided into aerobic or anaerobic reaction.In an aerobic cathode,oxygen is the terminal electron acceptor,and under anaerobic conditions,special compounds are used as electron acceptors.The air-cathode MFC can obtain oxygen as electron acceptor from the surrounding air,which not only reduces the amount of oxygen diffused into the cathode,but also reduces the energy consumed of fluid flow in the cathode chamber.Oxygen reduction reaction（ORR）is an important cathode reaction,and its slow kinetics seriously hinder the performance of air-cathode MFC.The use of catalyst can reduce the activation energy,accelerate the progress and reduce the activation loss of ORR.Noble metal catalysts are used as model for catalysis due to their high-efficiency catalytic activity.However,their high cost and poor stability have severely restricted the large-scale application of MFC.Not only that the structure of air-cathode MFC also affects its output performance.As the proton exchange membrane（PEM）that separates the cathode and anode and transfers protons,it has an inherent obstacle to the transmission of protons,which will cause ohmic loss.The removal of PEM can greatly reduce the internal resistance of MFC and the loss of proton transfer.However,for the single-chamber MFC,the cathode is directly exposed to electrolyte rich in microorganisms after the removal of PEM.And the biofilm will be reduced after long-term operation.The biofilm will grow on the surface of cathode after long time operation,which will also increase the internal resistance and affect the diffusion of H⁺to cathode.Therefore,exploring a catalyst with high efficiency,stability and low cost can effectively increase the output performance of MFC.At the same time,a reasonable design of dual-function catalysts with strong antibacterial effects will be more practical for further improving the performance of MFC and reducing equipment costs,and it will promote the market application of MFC.Metal-organic frameworks（MOFs）are widely used as self-sacrificing precursors to prepare porous carbon due to their excellent design,controllable pore structure and structural diversity.The g-C₃N₄ is rich in pyridine nitrogen atoms and graphene sheet structure,which can adsorb metal ions uniformly,so regarded as high-quality nitrogen source and support template.The combination of MOFs and g-C₃N₄ can give full play to the advantages of both,deriving a series of oxygen reduction catalysts with high-efficiency and multifunctional catalytic performance that can future improve the performance of MFC.The main research results are as follows:（1）Cobalt/nitrogen co-doped Cu-based metal-organic frameworks（HKUST-1）derived carbon materials modified by in-situ carbon nanotubes（Cu Co@NCNTs）were synthesized by direct immersion and pyrolysis.The carbon nanotubes induced by cobalt and the highly active bimetallic active sites formed by nitrogen doping made Cu Co@NCNTs have the best ORR performance in alkaline electrolytes.The limiting current density reached up to 5.88 m A cm^-2,and the onset potential was 0.91 V（vs.RHE）.The maximum power density of MFC with Cu Co@NCNTs as cathode catalyst(1255 m W m^-3)was even higher than that of Pt/C catalyst(1087 m W m^-3).（2）Based on the properties of Cu nanoparticles with strong antibacterial properties in Cu Co@NCNTs nanocomposites with high performance,Cu Co@NCNTs was applied to the MFC of without PEM to inhibit the formation of biofilm on the cathode surface.Cu Co@NCNTs showed obvious antibacterial activity and inhibited the biofilm on the cathode surface in antibacterial testing and biomass quantification.The power output of MFC supported on Cu Co@NCNTs(2757 m W m^-3)catalyst was significantly higher than the MFC of Pt/C(2313m W m^-3),and much higher than other non-noble metal catalysts supported MFC with PEM.Moreover,Cu Co@NCNTs showed excellent long-term stability in continuous operation because of its unique ability to inhibit the formation of biofilm.（3）The cost-effectiveness analysis of MFC after the use of MOFs-derived cathode catalyst and the removal of PEM was carried out.It was found that the MOFs-derived cathode catalyst with anti-biological pollution could not only replace the expensive Pt/C catalyst,but also simplify the structure and composition of single-chamber air-cathode MFC,avoiding the use of high-cost PEM.In this way,the performance of MFC was improved and the overall cost of MFC was greatly reduced,which was conducive to promoting the large-scale application of MFC.