| Lithium/air battery as secondary battery has widely prospective application, which is attributed to its theoretical specific energy are as good as that of petrol. The charge-discharge performance of lithium air battery is closely related to oxygen reduction reactions(ORR) and oxygen evolution reactions(OER) of the oxygen electrode and the Au Pt nanoparticles have high catalytic abilities on ORR and OER. Electrodeposition of Au Pt nanoparticles catalysts possesses many impressive performances such as simplicity and loading mass can be controlled, etc. Although there are many excellent properties, the Au Pt nanoparticles produced by electrodeposition still have some defects such as large grain sizes and low activity areas, etc. The application of a magnetic field during the electrodeposition can influence mass transfer and nucleation processes of the metal ions. In this paper, Au Pt nanoparticles were electrodeposited on carbon paper(CP) or loaded carbon power(C) onto the surface of carbon paper. The effects of magnetic field on electrodeposition process of Au Pt nanoparticles as well as catalytic abilities of the nanoparticles in lithium air battery were investigated.Through changing the concentration ratio of metal ion, it is found that when the electrolyte contains 8 mmol · L-1 HAu Cl4, 12 mmol · L-1 H2 Pt Cl6 and 0.5 mol·L-1 H2SO4, the current density is 20 m A · cm-2, and the electrodeposition time is 25 s, Au0.5Pt0.5 nanoparticles with high catalytic abilities on ORR and OER in EMI-TFSI/LiTFSI electrolyte can be electrodeposited. The lithium/air battery assembled with this CP/C/Au Pt electrode possessed a discharge and charge platform of appropriately 2 V, and retained a discharge-charge capacity of 600 m A · g-1 within 13 cycles at current density of 0.05 m A · cm-2.The cyclic voltammetry results show that co-deposition potential of Au Pt alloy is 0.2 V vs. SCE or more negative. Polarization curve analyzes indicated that the limiting diffusion current density decrease with the increase of magnetic flux density increase when a parallel magnetic field is added in the electrodeposition process. However, the variation tendency of limiting diffusion current density is completely reverse when a perpendicular magnetic field is added in the electrodeposition process. The additional magnetic field has almost no influence on electrodeposition process when the potential of Au Pt alloy is-0.25 V vs. SCE or more negative.The catalytic abilities of Au Pt nanoparticles on oxygen gradually increase with the rising magnetic flux density from 0.5 T to 2 T during constant current electrodeposition. The discharge-charge capacity of lithium/air batteries assembled with the CP/C/Au Pt electrode electrodeposited by added parallel magnetic field of 2 T and perpendicular magnetic field of 2 T are 3500 and 2800 m A h · g-1 respectively at the same current density of 0.05 m A · cm-2 as well as charge platform of 2.5 V.The Au Pt nanoparticles electrodeposited by constant potential have higher catalytic abilities than that of the nanoparticles electrodeposited by constant current. Moreover, the constant potential electrodeposition also overcomes the influence of current density on catalytic abilities of Au Pt nanoparticles. The best catalytic abilities of Au Pt nanoparticles on oxygen were obtained at deposition potential of-0.1 V vs. SCE, parallel magnetic field of 1 T as well as perpendicular magnetic field of 0.5 T. The discharge-charge capacity of lithium/air batteries assembled with the CP/C/Au Pt electrode electrodeposited by applied parallel magnetic field(2 T) and perpendicular(2 T) magnetic fields are 3800 at the current density of 0.05 m A h · cm-2 as well as charge platform of 2.5 V. |
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