Preparation And Application Design Of Metal Oxide Catalyst For Metal Air Fuel Cells

Metal-air cells as a kind of green energy sources has obtained the widely approval because of its richness,low cost,simple preparation technology and environmental friendliness.Magnesium anode reaction rate is much higher than air cathode oxygen reduction rate of air electrode,so improving performance of air electrode can enhances the MAFC performance.The catalytic properties of catalysts determine the performance of air electrode,thus developing a new type of efficient catalyst is becoming the focus of metal-air fuel cells research.The amorphous Mn O₂ catalyst with large lattice defects is prepard at room-temperature to increase catalystic active sites.Hydroxy carbon nanotubes intertwined formed a large number of mesopores,and the combinations of Mn O₂ with CNTs-OH is firm because of the strong adsorption ability of hydroxy group,thus improve stability of the catalyst.This combination can enhance the electrical conduction,strengthen the oxygen transfer,dispersity of catalyst and then improve the capacity of catalyst for oxygen reduction.The electrochemical tests show that the performance of Mn O₂/CNTs-OH catalyst is high:The initial reduction potential is 0.032 V vs Hg/Hg O,the half wave reduction potential is-0.175V vs Hg/Hg O,the electron transfer number is 3.89,and the Tafel slope value is 88.9m V/dec.In metal air cells performance test,the peak power density of magnesium air cell and aluminum air cell are 77m Wcm^-2,100.5m Wcm^-2 respectively.Mn Co₂O₄ with high catalytic activity was synthesized by adjusting the Mn atom ratio of manganese cobalt oxides,and rare earth element La was doped into Mn Co₂O₄ to further regulate the crystal structure.The electrochemical tests show that the performance of La _x Mn_1-x Co₂O₄/3d-C catalyst is the highest,in which the initial reduction potential is 0.038V vs Hg/Hg O,the half wave reduction potential is-0.102V vs Hg/Hg O,and the electron transfer number is 3.96.In metal air feul cells performance test,the peak power sensity of magnesium air fuel cell is 71.5m Wcm^-2.Considering the influence of metal composite oxide crystal phase,structure and morphology,on the catalytic performance,the spinel Co Fe ₂O₄and amorphous Co Fe₂O₄ were prepared by solvothermal synthesis.A variety of carbon materials were used to immobilize the composite oxide solid which could improve the electrical conduction ability,strengthen the oxygen transfer.The electrochemical tests show that the Co Fe₂O₄/3d-C is an excellent bifunctional catalyst whose initial oxygen reduction potential is 0.01 V vs Hg/Hg O,half wave reduction potential is-0.121V vs Hg/Hg O,the electron transfer number is 3.92,the oxygen evolution reduction potential is 0.524V vs.Hg/Hg O.The peak power density of magnesium air cell is 66m Wcm^-2.C₃N₄ which can effectively prevent the cluster layer stack of catalysts,increase specific surface area,improve the catalyst performance is prepared from dicyandiamide by melting method.The catalysts?Co C ₃N₄@Si O₂/C,Mn C₃N₄@Si O₂/C and C₃N₄@Si O₂/C?which can increase the high catalytic activity of metal-nitrogen-carbon bonds to further enhance the catalyst performance are prepared through pyrolyzing C₃N₄@Si O₂ and transition metal salt.The electrochemical tests show that the catalystic performance of Co C₃N₄@Si O₂/C is the best,whose initial reduction potentials are 0.015V vs Hg/Hg O in 0.1M KOH solution,0.487V vs SCE in 0.1M HCl O₃ solution.In magnesium air cells performance test,the peak power density is 66m Wcm^-2,and Co C₃N₄@Si O₂/C catalyst as the cathode catalyst,shows good catalytic performance in mental-air cells.