Design And Construction Of Platinum Alloy Catalysts With Starfish-like And Core-shell Structures And Their Electrocatalytic Performances

Proton exchange membrane fuel cell?PEMFC?is considered as one of the most promising new energy technologies in the 21st century due to its high energy efficiency,low pollution,high safety and derive from a wealth of sources.Catalyst is one of the most important part of PEMFC.Currently,the most widespread catalyst of PEMFC is commercial Pt/C catalyst,but a series of problems still exist,such as the rare reserves and high cost of platinum,and in the harsh electrochemical operation environment,Pt particles in commercial Pt/C catalyst may move,fall off or reunion,lead to the reduction of the catalyst stability,which seriously hindered the spread and application of proton exchange membrane fuel cell.Therefore,it is of great significance to develop platinum alloy catalysts with lower price to replace noble metal platinum catalysts.Based on the research experience of the frontier,in this paper,we have increased the number of active sites and the utilization and stability of Pt atoms by the means of alloying and construction of core-shell structure,as a result,the activity and stability of platinum-based catalyst are greatly improved.At the same time,the introduction of relatively cheaper transition metal such as Cu and Ni can reduces the usage of platinum and thus greatly reduce the cost of fuel cell catalysts.The specific experiment is as follows:First,in this work,we prepared PtCu/C and PtCuNi/C catalyst by a simple co-reduction method.Then we used transmission electron microscope?TEM?,X-ray diffraction?XRD?,inductively coupled plasma-optical emission spectra?ICP-OES?,X-ray photoelectron spectroscopy?XPS?to characterize the morphology and composition of the platinum alloy catalyst,most importantly,we used cyclic voltammetry?CV?and linear sweep voltammetric?LSV?methods to test the electrocatalytic activity and stability.The results showed that the PtCu alloys prepared by co-reduction method present a homogeneous spherical morphology,but in the case of other conditions unchanged,introduce Ni elements can turn the morphology into a starfish-like structure.The electrochemical tests show that the half wave potential(E_1/2=0.915 V)and mass activity(MA=0.58 A mg_Pt^-1)of the PtCuNi/C catalyst in acidic media are much higher than those of 20%commercial Pt/C(E1/2=0.85 V,MA=0.10 A mg_Pt^-1).At the same time,it also has better stability in comparison with commercial Pt/C.After 5000 cycles,PtCuNi/C catalyst shows only 10.7%decline in mass activity,while 41%for Pt/C.Thereafter,we designed and synthesized a dodecahedral Pd@PtCu nanocrystal with a core@alloy-shell structure by a simple seed-mediated approach.Because of the lattice regulation of PtCu alloy and the synergistic effect between Pd core and PtCu shell.The Pd@PtCu catalyst with dodecahedron core-shell structure showed excellent ORR performance,the mass activity is 6 times higher than commercial Pt/C?0.9 V vs RHE?,At the same time,its HER performance is also far superior to Pt/C,the mass activity is 25 times than that of Pt/C?0.025V vs RHE?.Most importantly,the stability of HER and ORR of the catalyst was also much higher than that of commercial Pt/C.