Preparation Of Carbon-based AuPt Composite Electrode And The Catalytic Performance For ORR/OER

In recent years,with the rapid development of new energy industry,the secondary battery as an important energy storage equipment also received widespread attention and development,the lithium air batteries because of its high theoretical specific capacity and specific energy,is considered to be the most potential secondary battery.Lithium air batteries with oxygen as a reactant,will occur the oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?on the oxygen electrode.The appropriate bifunctional catalyst can effectively reduce the over-voltage,enhance the cycle performance of positive electrode materials.AuPt noble metals have high catalytic activity for ORR and OER.To prepare the catalyst with small size and uniform dispersion can improve the catalytic performance of the catalyst.Electrodeposition technology is a low cost and simple technology of in situ preparation of nanocrystalline metal catalyst.In this paper we will mainly study the influence of electrode substrate and preparation process on the catalytic properties of Au Pt alloy.So that it is possible to prepare a bifunctional catalyst for an air electrode having a high catalytic performance.Firstly,the electrodeposition process of AuPt alloy was researched by cyclic voltammograms?CV?and polarization curve?LSV?,indicated mainly exist the deposition of Au,the transformation of Pt and the codeposition of AuPt.Through the study,we decided-0.3 V as the deposition potential.Research shows when the total concentration of salt in the bath was 20 mmol·L^-1,the deposition process of AuPt was a mixed controlled by a combination of electrochemical and diffusion control,the diffusion coefficient?D?of Au ions in the liquid was 5.6172 × 10^-5 cm2·s^-1,according to the Scharifer and Hills?SH?model the nucleation process of AuPt was closer to instantaneous nucleation,which was advantage for the preparation of nanocatalyst.Subsequently,the performance of AuPt alloy was compared with that used Carbon Paper?CP?,Carbon Paper/Graphene sheets?CP/GNs?or Carbon Paper/Ketjen Black?CP/KB?as the substrates.It was found that CP/GNs were better.In contains 8 mmol·L^-1HAuCl₄,12 mmol·L^-1,H₂PtCl₆,0.1 mol·L^-1HCl in the plating solution,deposition time was 25 s,the AuPt alloy,can be obtianed with particle size 100 200 nm on the electrode surface at the same time there is also have some AuPt alloy agglomeration which the size was more than 200 nm on the electrode surface.The X-ray photoelectron spectroscopy?XPS?test showed that the contents of Au,Pt on the electrode were 5.06 at%,2.81 at%,respectively,the rest were C and O.The Eo?the potential when j = 0.03 mA·cm-2 by LSV?of CP/GNs/AuPt electrode catalytic for ORR is 0.87 V?vs.RHE?.The ORR process is a four-electron reaction,and the dynamic current density can reach 32 mA·cm-2.The Eo of CP/GNs/AuPt electrode catalytic for OER is 1.69 V?vs.RHE?.To reduce the total concentration of main salt in the plating solution,when HAuCl₄ concentration is 0.8 mmol·L^-1,H₂PtCl₆ concentration is 1.2 mmol·L^-1,AuPt alloy catalyst particle size decreased to 100 150 nm,energy spectrum?EDS?tests showed Au content is 55.74 at%,the content of Pt 44.26 at% in AuPt alloy.The Eoof CP/GNs/AuPt electrode for ORR is 0.85 V?v.RHE?.In low concentration of main salt solution adding 60 mg·L^-1 glycolic acid as additive,the diffusion coefficient of plating solution decreased to 7.2263×10-6 cm2·s^-1,deposite 35 s to prepare CP/GNs/AuPt electrode and the particle size of AuPt alloy less than 100 nm;The XPS test showed that the content of the Au and Pt elements were 0.81 at%,0.59 at%,and the load was significantly reduced.The X-ray diffraction?XRD?analysis showed that there were more high index crystals?200?,?220?and?311?.The electrode catalyzed ORR to follow the four electronic process,and Eo improved to 0.88 V?v.RHE?and the kinetic current density of the electrode increased to 80 mA·cm-2.The AuPt alloy catalyst prepared under this condition for the OER is 1.67 V?vs.RHE?.