Structural Regulation Of Pt-Based Anode Catalysts And Their Electrocatalytical Performance

Platium-base catalysts are widely used in the field of fuel cell,petrochemical industry and other important areas.Being limited by the shortage of stock and high price,it is always very necessary to improve the activity,stability and utilization efficiency of Pt-base catalysts in related application fields.High overpotential,surface poisoning,low selectivity and agglomeration were main shortcoming of Pt-base catalysts used as the anode of fuel cell.Previous studies have illustrated that the activity of catalysts is strong correlated with the size,dispersion,surface and electronical structure.This work aims to improve the activity and antipoisoning ability of Pt-base catalysts.By different strategies such as alloying,support effect,and shape-control,the synergistic effect between Pt and other metals/metal oxides is utilized sufficently which promoted the activity of catalysts.Main research contents and corresponding results were listed below.(1)Uniform CeO2 nanorods(CeO2-r)and CeO2 nanoparticles(CeO2-p)are synthesized by hydrothermal method.HRTEM images indicate that the synthesized CeO2-r are covered by(100)and(110)facets which own higher surface energy compared to CeO2-p with(111)facets.Uniform Pt nanoparticles are prepared by glycol reduction and combined with CeO2 as catalysts(indexed as Pt/CeO2-r&Pt/CeO2-p)for methanol electrooxidation.According to the characterization of XPS,the binding energy of Pt 4f shift positively and the content of Pt-O species increased to 52%and 49%in Pt/CeO2-r and Pt/CeO2-p respectively,illustrating the existence of Pt-O-Ce.Electrochemical characterizations further demonstrate the sufficient contact between Pt and CeO2 by the observation of H spill-over effect.Pt/CeO2-r shows excellent specific activity(peak current:7.5 mA·cm-2)towards the electrooxidation of methanol which is 1.6 and 10 times higher than Pt/CeO2-p and commercial Pt/C-JM.By in-situ FTIR spectroscopic investigation,much higher CO2 productivity is observed at low potential on Pt/CeO2-r that implies strong anti-poisoning ability during methanol electrooxidation.The significant improved electrocatalytical performance is attributed to the existence of CeO2 nanorods with high energy surfaces.(2)In addition to this,bimetallic PtPb single-crystalline nanodendrites(PtPb SND)are synthesized via a facile one-pot method.The alloying of Pt and Pb is evidenced by the characterization of XRD and TEM.By SAED,we observed the special single-crystalline structure of PtPb SND.The segregation of Pb atoms on the near surface of PtPb SND is demonstrated by EDS,ICP-AES and XPS results.By a series of controlled experiments,the morphology revolution of the dendritic structure is attributed to the combined result of Pb UPD,oxidative etching and specific absorption of halogen ions.Benefiting from the highly branched geometric construction and electronic structure influenced by the addition of Pb atoms,the as-prepared PtPb SND showed excellent activity and improved anti-poisoning ability for electrooxidation of formic acid.The massic activity at 0.1V(vs SCE)reaches to 2.7 A·mg-1 which is 4.4 times higher than Pd black and 38 times higher than Pt/C-JM.No adsorbed CO peak could be detected on PtPb SND even at relative low potentials by the characterization of in situ FTIR,illustrating that the indirect reaction pathway of HCOOH electrooxidation is severely inhibited which greatly releases the active site of catalysts.