Preparation Of Cobalt-nickel-based Composite Material Modified Anode And Its Application In Microbial Fuel Cell

Microbial fuel cells（MFCs）have attracted the attention of scholars in the field of sustainable energy due to their clean and low-cost advantages.As a system that combines biology and electrochemistry,MFC can oxidize organic matter while generating electricity.At present,the limitation of MFC is that the power generation performance needs to be improved,and anode modification is one of the main ways to improve the performance of MFC.This dissertation mainly studies the preparation of Co-Ni-ZIF materials and their derivatives.Based on the porous properties of Co-Ni-ZIF materials and the good electrocatalytic activity of their carbonized derivatives,a series of studies have been carried out.And these materials were used as MFC anodes to analyze the power generation and energy storage performance of MFC.The Co-Ni-ZIF electrode and its phosphating derivative electrodes with different ratios were prepared with titanium mesh as the matrix,and the 1:4 phosphating derivative electrode had the best electrochemical performance.The scanning electron microscope（SEM）characterization shows that the Co-Ni-ZIF material has a dodecahedral structure,which can still maintain a certain polyhedral structure after phosphating.The results of X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）show that its phosphide is mainly composed of Co and Ni phosphide.When it is applied to the MFC anode,the overall power generation performance of the MFC is significantly improved compared with the Co-Ni-ZIF anode MFC,and the maximum power density is 4.511 W/m³,which is 2.18 times that of the Co-Ni-ZIF anode MFC.Through high-throughput tests,it was found that the dominant bacteria genus on the anode surface of 1:4 phosphating derivatives was Geobacter,and the proportion was 60.83%,which was higher than the proportion of the dominant bacteria on the surface of Co-Ni-ZIF anode.It shows that the addition of P element promotes the selective enrichment of electricity-producing microorganisms,and Geobacter bacteria with high-efficiency electricity-producing ability become the dominant bacteria genus,which improves the electricity-producing ability of the anode.The Co-Ni-ZIF@C electrode was prepared by carbonizing at high temperature on the basis of Co-Ni-ZIF material with titanium mesh as matrix.At the same time,the optimal temperature was screened with different temperatures as variables.The SEM test shows that with the increase of carbonization temperature,the structure of the material collapses,and it completely collapses and agglomerates at 900℃.The materials synthesized at 800℃showed a uniform spherical shape with a wrinkled surface,which was conducive to the attachment of microorganisms.XRD and XPS analysis results show that Ni and Co in the material mainly exist in the form of single metal,but some oxidation occurs.When used as MFC anode,the R_ctof Co-Ni-ZIF@C-800 anode is 4.050Ωthrough AC impedance test.At the same time,the maximum power density reaches 5.86 W/m³,which is 30%higher than that of phosphide derivative anode MFC.Finally,the Co-Ni-ZIF@CN electrode was prepared using titanium mesh as the matrix and composites prepared from Co-Ni-ZIF and polyaniline（PANI）with different mass ratios as the precursor.The morphology of Co-Ni-ZIF was observed by SEM,and it was found that the addition of polyaniline did not affect the structure of Co-Ni-ZIF itself,and at the same time could reduce the degree of collapse after carbonization.The XRD results show that the oxidation degree of Co and Ni in Co-Ni-ZIF@CN material is significantly lower than that of Co-Ni-ZIF@C material,which can better exert the high activity of Co and Ni particles.At the same time,the addition of PANI introduces the N element,which improves the overall biological affinity.According to the spectral results of N 1s in XPS,the contents of pyridine N and graphitic N in the material are increased compared with Co-Ni-ZIF@C,which can improve the electrocatalytic activity of the material to a certain extent.When Co-Ni-ZIF@CN-15%is used as MFC anode,it can store a charge of 37521 C/m² under the condition of charging for 45min.And the maximum power density of MFC is 8.67 W/m³,which is 47%higher than that of Co-Ni-ZIF@C anode MFC.