Preparation Of Platinum Based Catalysts And Their Electrocatalytic Performances

Direct methanol fuel cell?DMFC?has been widely concerned as a novel energy equipment which can replace traditional combustion power generation because of its high efficiency and no pollution.However,platinum,which is used as electrocatalyst in DMFC,is a noble metal with limited reserves and expensive price.High cost has become the main obstacle to the large-scale industrialization of DMFC.How to further reduce the amount of Pt in the catalyst and improve its activity and stability is one of the keys to realize the industrialization of DMFC.In this work,new types of Pt based nanomaterials with different morphologies have been designed and synthesized by simple and effective methods.The morphology,structure and composition of materials were tested by scanning electron microscope?SEM?,transmission electron microscopy?TEM?,high resolution transmission electron microscopy?HRTEM?,energy dispersive spectroscopy?EDS?and so on.The catalytic performance and stability of the materials for oxygen reduction reaction and methanol oxidation reaction were also tested in the acid electrolyte.The main contents and results of this work are as follows:?1?We demonstrate a simple strategy for the preparation of ultra-dispersed surface-clean Pt catalyst with high stability,in which the Pt nanoparticles?NPs?with 1.8±0.6 nm in size are anchored tightly on a 3D hierarchical porous graphitized carbon?3D-HPG?through galvanic replacement reaction.The as-obtained catalyst displays the higher catalytic activities for both ORR and MOR compared with commercial Pt/C.The Pt NP/HPG can undergo 2000 voltage cycles with negligible activity decay and no apparent structure and size changes for MOR during the durability test,and its mass activity for ORR only reduce 18.3%after 5000 cycles.The excellent performance is attributed to strong anchoring effect between carbon support and Pt nanoparticles.?2?We report a liquid-phase chemistry method to synthesize Pd@PtNi core-shell nanowires?NWs?with helical PtNi shells,which are bounded with high-index facets.The Pd nanowire as a template guides the epitaxial growth of PtNi,retaining the appearance of one-dimensional nanowires.Ni regulates the rate of atomic deposition/diffusion and promotes the formation of high-index facets.Using pure Pd nanowire as core significantly reduces the content of Pt in the catalysts,with the mole ratio of Pt/Pd/Ni=1/3/0.27.The as-synthesized Pd@PtNi NWs exhibit an outstanding catalytic performance for oxygen reduction reaction?ORR?.The mass activity and specific activity are 1.75 A mg_pt^-1 and3.18 mA cm^-2,which are 10 times and 12 times of the commercial Pt/C catalyst,respectively.In addition,the one-dimensional nanostructure enables the catalyst to be highly stable after 30,000 potential sweeping cycles with a decay of only 17.7%for ECSA.