| Proton exc hange me mbrane fue l cell(PEMFC) has been used w idely as che mical power, because of its simple structure, high ener gy dens ity, high energy conversio n effic ie ncy, and environmenta lly frie nd ly. The anode of hydro gen- oxyge PEMFC reactio n rate is quick ly and P t/C nanopart icles catalysts ha ve high catalyt ic activit y and excelle nt che mica l stabilit y, but the cathode reactio n rate is slow a nd the potent ia l of the oxyge n electrode more ne gative, so how to impro ve fue l battery cathode catalyst activit y and reduce the cost of the catalyst, has beco me one of the focus of the fuel cell.Pt catalysts are the most co mmo nly used in proton exc hange me mbrane fue l cell due to its high catalyt ic activity and stabilit y, but the high cost o f Pt catalysts and its shorter service life are greatly preve nt ing its fro m w idespread commerc ial applicatio n. For the purpose of impro ving the catalyt ic activit y and reduc ing the cost of fue l cell, one way is to allo y Pt w it h transit io n metals suc h as Fe, C o, N i etc. Howe ver, catalyt ic reaction mec ha nis m o f anot her compo nent o f the Pt- doped improving the perform ance of the electrocatalyst is not fully understood in the reaction process.X-ray absorption fine struct ure(XAFS) technique based on sync hrotron radiat ion has ele me nt se lectivity a nd can detect the local geo metr ic and electronic s truct ure for both metal ele me nts of the bimeta llic nanopartic les catalysts of fuel c ell respective ly, and can be used in studies the catalysts structure cha nges of fue l cell by in sit u experimenta l methods, co mb ines wit h other characterizat ion techniques, suc h as trans missio n electron microscopy(T EM) and X- ray diffractio n(XR D), provides comp le me ntar y struct ural infor mat io n, inc luding the vale nce che mistry, coordinatio n number, bond distance, etc. In this paper, the catalysts of fue l cell were studied by in situ X AFS technique on Bea mline B L14W1 at the Shanghai Synchrotron Ra d iatio n Facilit y(SSRF), and in situ XAFS techniq ue was deve loped. C o mb ining w it h TEM, XR D and XAFS techniq ue, the struct ure cha nges and the relat ions hips between the double metal co mpone nts in the reactio n process of Pt-based bimeta llic catalysts were stud ied by syste mat ic analys is. The ma in results of this paper are show n as follow ing.(1) We establis hed and developed an in situ X-ray absorption fine struct ure experimenta l testing device fo r characterizing hydroge n-oxyge PEMFC on XAFS bea mline B L14W1 at SSRF. X AFS data were collected under the operating state of the fue l cell w ith Pt/C and Pd/C as the cathode and anode catalysts, re spective ly, w hile the cell C- V and power dens ity c urves were mo nitored. C hanges in the oxidat io n states of the Pt/C catalyst were observed during the reaction process at differe nt potentia ls. Strong Pt-O bonds on the s urfaces of t he Pt were found to be induced at high potent ia l; this ma y hinder the perfor ma nce of Pt and reduce its oxyge n reductio n reaction(O R R) activit y. The stud y also ver ified the reliab ilit y and feasibility of the herein established experimental apparatus and technique.(2) Three co mmercia l catalysts of fue l cell were characterized by in situ X AFS techniq ue establis hed : HS- Pt/C, JM- Pt/C, JM- Pt Ru/C. As the volta ge of fue l cell gradua lly decreased, HS- Pt/C and JM- Pt/C were gradua lly reduced in the reactio n process, but JM-Pt R u/C was gradually reduced at high potent ia l and was oxid ized at low potentia l. The key factors affecting the catalysts activit y is the ratio of zero va lence Pt, the presence of Pt-O bond can be suppressed Pt/C catalysts activit y, the ele me nt of R u does not enha nced Pt catalysts O RR activity, but occupys active sites of Pt, it leads to decreased activity of JM-Pt Ru/C catalysts.(3) Pt Co/C bimeta llic nanopartic les catalysts were for med fro m Pt doped trans it ion metal ele ment of C o. Due to the presence of C o can influe nce the extent of Pt oxidat io n, the meta l Pt latt ice beco mes s maller and Pt- Pt bond lengt h shortened compared w it h co mmerc ia l Pt/C catalysts. Pt C o/C has a s maller nanopartic les size and reduces the distance between t he Pt-Pt bond, thereby improving the catalysts activit y of Pt Co/C. There are more d orbital vacancies co mpared transit io n metal C o w ith Pt. The results of in situ XAFS experime nts reveal d electrons of Pt trans fer to transit io n metal C o in the reactio n process, Pt d- band vacanc y increase is cond ucive improve perform ance Pt catalysis ORR activity.In summar y, in sit u X AFS method for fue l cell catalysts was successfully achie ved on bea mline B L14W1 at SSRF, experime nta l cond it ions were optimized a nd realized for the collectio n of o nline XAFS data. This paper provides in situ XAFS experimenta l met hod for the research of PEMFC catalysts struct ure changes, includ ing deve lop me nt and building the test device, technica l optimized testing, analys is collect ing online data. It also provides a new method to carry out in sit u XAFS study of fuel cell catalysts using SSRF. |
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