Structural Regulation And Oxygen Reduction Performance Of Platinum-based Nanowires

Maximizing the platinum(Pt)utilization efficiency is crucial for the industrial-scale commercialization of proton exchange membrane fuel cells(PEMFCs).For Ptnanoparticles,the specific activity decreases monotonically with the size decreasing due to the size optimization is limited by the size effect.However,the ultrafine Pt-based nanowires(NWs)with diameter less than 3 nm are less limited by size effect,because the specific activity increased with the decrease of diameter.Currently,researches on Pt-based NWs were mainly focused on improving oxygen reduction reaction(ORR)catalytic performance,while the dominant factors for enhanced ORR performance and the size effect different from Ptnanoparticles have not been studied deeply.Herein,the size tunable Pt-based NWs(< 3 nm)were employed as the model catalysts to study the dominant factor and the size effect different from Ptnanoparticles behind the performance enhancement of PtNWs in ORR.We also investigate the method for the in-situ growth of Pt-M NWs(M = Ni,Mo)on carbon black(CB)and graphene oxide(GO)support,which is beneficial for the practical application of ultrathin Pt-based NWs via simplifying the preparation process and optimizing the ORR performance.Firstly,PtNWs with different size are synthesized by regulating the dosage of the precursors and the temperature.The ORR results indicate that the PtNWs with different diameters(1.1,1.5 and 2.4 nm)showed better ORR performance than commercial Pt/C,and the ORR performance increased with the decrease of diameter.The combination of structure analysis and theory calculations reveal that the compressive strain on PtNWs enhanced the ORR performance.Besides,the compressive strain is the dominant factor on ORR performance in PtNWs,while the low coordination number is the dominant factor on ORR performance in Ptnanoparticles.As a result,the size effect of ultrafine PtNWs is different from that of Ptnanoparticles.Subsequently,in order to develop a facial preparation method of PtNWs for industrial applications,an in-situ growth strategy was proposed to simplify the synthesis process,and four catalyst materials,PtNWs@CB,PtNiMo NWs@CB,PtNWs@GO and PtNiMo NWs@GO,were successfully prepared.The ORR measurements indicate that PtNiMo NWs@CB showed better ORR performance than other catalysts and commercial Pt/C,highlighting its great potential toward practical application.This work not only provides deep insights into the size effect of PtNWs for ORR but also provides an in-situ growth method to simplify the preparation process and enhance the ORR performance.Results obtained in this work can not only help to gain deeper understanding of the catalytic mechanism of PtNW s in ORR,but also provide a simple catalyst preparation process for their practical applications.