Study Of Pd Induced Pt(â…£) Reduction To Form Pd-Pt/SH-CNT Bimetallic Catalyst For ORR

Proton exchange membrane fuel cells （PEMFCs） are considered as one ofpromising techniques to cut down carbon emissions and petroleum use. In spite of manyattempts by researchers to create a non-Pt catalyst for low temperature （<200℃） aircathodes, Pt/C remains the state-of-the-art catalyst at least for acid-based fuel cells.However, two drawbacks of such catalysts obstruct Pt/C catalysts commercialapplications. One is high costs of Pt if Pt usage maintains the level of the currenttechnique, another one is the deterioration in activity caused by corrosion of the carbonsupport. Therefore, looking for a more active catalysts and more stable catalyst supporthas been a hot topic in PEMFCs.From the above, a new catalysts Pd-Pt/SH-CNT, on the one hand, prepared byreduce the Pt content, improve the utilization rate of Pt; on the other hand, Pd directlylinking-SH on CNTs surfaces to increase active site and to improve the specific surfacearea and stability. In this paper, combining with experiment and calculation method, wereport a Pd-Pt/SH-CNT bimetallic catalyst synthesized by Pd inducedinduced Pt（Ⅳ）reduction on Pd/SH-CNT. Based on a fact that CNTs have abundant free-flowing Ï€electrons, it makes them potential reductants for reactions needing electrons. Pt4+ionsreduction on the thiolated CNTs （SH-CNTs） is catalyzed by beforehand deposited Pdparticles on the SH-CNTs. Experiments show that the catalyst activity has obviouslyimproved compare with the commercial Pt/C. To reveal the phenomenon, the DFTcalculation was performed.We also calculated the species HOO and O on near surfacesPdPt alloys. The results show that a surface at-om for ratio of1:3for PdPt showssuperior ORR activity. And the results also show the activated of HOO*species onPd3-Pt alloy decomposes to adsorbed O*and OH*s-pecies with its activation barriersmall.We reveal that Pd Pt/SH-CNTs bimetallic catalyst with Pt rich on the Pdnanoparticles surface particle size is about4.6nm. In this case, Pd not only used as aseed which would form a capping Pt to tailor the structure and improve the dispersion ofnanoparticles，but also promote the self-reduction rate of Pt. Different proportions ofPd/Pt have different surface area activities （SAs） were1.5-4times than Pt/C catalyst（relative to the Pt mass）. The Pt mass was solely taken into account, the mass activities（MAs） of the Pd-Pt/SH-CNT bimetallic nanoparticles was7-9times that of the state-of-the-art Pt/C catalyst for PEM fuel cells. According to the change Pd/Pt ratio canbe found that the Pd₂-Pt₁/SH-CNT is the best catalyst, whose electrochemical surfacearea is80.2m²Â·g^-1Pt, the specific activity is1.98A·mg^-1Pt.