Post-treatment Regulation Of Surface Morphology And Surface Compressive Strain Behavior Of PtCe Catalysts

Platinum(Pt)has been widely used in the fields of fuel cell,purification of exhaust gas,petrochemical industry and preparation of hydrogen energy due to its special electronic structure(empty D orbit),which endows it with high catalytic activity and catalytic stability.However,pure Pt/C catalyzer particles tend to aggregation in the process of catalytic reaction,which reduces not only the utilization but also the catalytic activity of Pt,hindering the practical application of Pt in industry and commerce,so that its excellent catalytic performance cannot be popularized in large scale.Therefore,to develop a low high catalytic activity of Pt based catalyst with low Pt content is a hot research topic in the field of fuel cells.In this work,PtCe/C alloy catalysts with different Ce content were prepared via ion beam sputtering(IBS)and subsequent vacuum heat treatment at 400?.The optimal Ce content was determined by the electrochemical performance of the alloy catalyst,so that the optimal samples could be corroded at different time.Afterwards,CV,LSV were used to analyses hydrogen evolution peak area and exchange current density of catalysts;inductively coupled plasma atomic emission spectrometry(ICP-AES),X-ray diffraction(XRD)were used to detect element contents of catalysts and phase components;high resolution transmission electron microscopy(HR-TEM&STEM)was used to characterize surface morphology,particle structure and lattice fringes of catalysts;X-ray photoelectron spectroscopy(XPS)was used to analyses valence change of surface elements.The results are as follows:(1)According to analysis of electrochemical catalytic performance,the best catalytic performance of PtCe/C obtains when the target shifts 30mm,and the exchange current density is closest to the value of pure Pt/C catalyst,thus the content of Ce is optimized.Then after treating the samples of optimum Ce content with electrochemical alloying,it is found that PtCe/C alloy catalyst corroded for 1 hour shows the best catalytic performance.Specifically,the exchange current density(i0)of PtCe/C increased by 45.18%comparing with pure Pt/C(3.94�10-3A/cm2),reached 5.72�13-3A/cm2;the integral area of hydrogen evolution peak increased by 115.51%comparing with pure Pt/C(2.45�10-4A�V),reached 5.28�10-4A�V,thus the contact area between catalyst and electrolyte is greatly increased;while Pt loadings decreased by 32.59%comparing with pure Pt/C(1.43�10-1mg/cm2),reached 9.64�10-2mg/cm2,which adequately reflects high catalytic activity with low Pt content.(2)XRD reveals that the Pt peak of PtCe/C alloy catalyst shifts towards a large degree with respect to pure Pt/C before and after corrosion,which indicates that the addition of Ce leads to a decrease in the interplanar crystal of Pt.Furthermore,after electrochemical alloy treatment,the Pt peak of PtCe/C alloy catalyst shifts to a larger degree,owing to a large amount of Ce is etched by dealloying treatment,and zero dimensional defects are produced,which not only reduces the interplanar spacing,but also forms nano porous honeycomb-like structure on the surface of the sample.Meanwhile the surface roughness and the specific surface area are increased.(3)As illustrated by the analysis of STEM&EDS and HR-TEM,after the electrochemical dealloying treatment,the particles with Pt as the main component are distributed uniformly in a size range of 6?10nm,and the relative content of exposed Pt increased,and the contacts with the reactants are more abundant.The interplanar distance of Pt is compressed,resulting in the decrease of the binding force between Pt and oxygen intermediate and the improvement of Pt catalytic activity.(4)XPS analysis manifests that the binding energy of the Pt4f peak of the samples moves to low energy region after the electrochemical corrosion,impelling Pt closer to the Fermi level,and the content of the compound state Pt2+ increases by 49.84%,and the electron cloud density is also increased.Meanwhile,there are a large number of high electronegativity and easily reduced lattice oxyge on the surface of the sample.These two consequences lead to the enhancement of the catalytic activity of PtCe/C alloy catalyst.