Preparation And Electrocatalytic Properties Of Platinum-based Heterostructured Metal Catalysts

Platinum(Pt)is an indispensable material in proton exchange membrane fuel cells(PEMFCs).However,the limited storage and excessive consumption severely restrict the sustainable development and wide application of Pt-based catalysts.Compared with gasoline-powered vehicles,the most important problem in the current PEMFCs is the high cost of Pt-based catalysts.Therefore,only when the cost of Pt-based catalysts is effectively reduced,PEMFCs can be more competitive in the future new energy vehicle market.In order to meet these challenges,we are committed to reducing the consumption of Pt,reducing the cost of the catalyst and improving the catalytic performance of the catalyst.Numerous studies have shown that the most effective way to improve the catalytic performance of the catalyst and reduce the Pt consumption is to alloy the Pt by introducing other metal elements,and to synthesize an alloy catalyst with high atomic utilization and open structure.This study mainly improves the catalytic activity and stability of the catalyst by alloying Pt with Cu,Ni,Co and other transition metal elements to obtain more efficient alloy nanomaterials.In addition,the morphology of the catalyst will also have a great impact on its performance.We prepare nanomaterials with more open structure and higher Pt atomic utilization rate.In order to improve the catalytic performance of the Pt-based catalysts for methanol oxidation reaction(MOR)and reduce the consumption of Pt,we have synthesized radial Pt-Co nanodendrites in one step by modified solvothermal method.It is worth noting that the radial Pt-Co ND can be well controlled by adjusting the amount of CTAC and reaction time.At the same time,radial Pt-Co nanodendrites possess the Pt-rich surface,and lots of tip regions which will promote electron transfer and mass exchange in catalytic processes,because their large number of first-order nanodendrites and closely connected secondary nanodendrites.In addition,radial Pt-Co nanodendrites have higher catalytic performance and stability in methanol oxidation than commercial Pt/C.This study provides more possibilities for the preparation of higher performance alloy nanodendrities catalyst materials.We have synthesized Pt-Cu-Ni rhombohedral dodecahedral framework(NF)by using improved solvothermal method and unique secondary etching method.As an intermediate product of the Pt-Cu-Ni nanoframe,Pt-Cu-Ni solid state nanocrystals can be well controlled by adjusting the reaction time and the amount of Ni precursor.Based on the formation mechanism of Pt-Cu nanoframes,we studied the growth mechanism and morphological evolution of ternary nanoframes.The morphology,atomic ratio and average particle size of nanocrystals have demonstrated the morphological evolution of Pt-Cu-Ni nanocrystals.The growth mechanism of Pt-Cu-Ni solid nanocrystals(SD)is also critical throughout the process compared to subsequent etching steps.The shape-tunable nanoframe catalyst exhibits superior catalytic performance in the oxygen reduction reaction(ORR).The Pt-Cu-Ni nanoframe catalyst exhibits a mass activity of 0.86 mg-1Pt at 0.9 V,which is 6 times higher than that of commercial Pt/C catalyst.It is worth noting that the Pt-Cu-Ni nanoframe catalyst has a more positive onset potential than most catalysts.More importantly,the improved solvothermal and secondary etching methods open the door to the development and application of nanoframe catalysts.To reduce the cost of the catalyst and the consumption of Pt,a facile electrochemical displacement preparation method has been proposed,and the nanostructures can be easily controlled by a strong reducing agent and a surfactant.Two distinct Pt-Co spheres,Pt-Co core-shell spheres(CSSs)and Pt-Co hollow alloy spheres(HASs)are successfully synthesized by changing the introduction of N2.Interestingly,the Pt-Co CSSs possess a Pt-rich shell with 7 atomic layer thickness,which promotes the efficient utilization of Pt atoms.Pt-Co HASs have a highly open structure and a single alloy phase.For MOR,the Pt-Co CSSs and Pt-Co HASs exhibit enhanced catalytic performances.Compared with commercial Pt/C catalyst,the mass activity of Pt-Co CSSs catalyst is increased by 4 times and have better stability.More importantly,the current work opens a door to batch preparation of Pt-based catalysts and synthesis of shell nanostructures.