Synthesis And Electrocatalytic Properties Of Aupt Bimetallic Nanoparticles

Fuel cell is a kind of chemical battery which can convert the chemical energy stored in fuel directly into electric energy efficiently and environment friendly through external circuit according to electrochemical principle.A single battery includes ion exchange membrane,electrolyte and two electrodes of postive and negative.Hydrogen oxidation reaction occures at the cathode and oxygen reduction reaction takes place at the anode.In theory,when the reaction materials such as hydrogen and oxygen are inputed,the reaction product water will be pumped,so fuel cells can discharge continuously.That is to say,the fuel cell in actual use is not affected by the capacity,as long as the continuous fuel supplies,continue electricity generates.As a result,fuel cells have been described as the fourth generation of generators after the internal combustion engine.Anodic catalyst is one of the most important technologies of fuel cell.Improving the catalytic performance and stability of anodic catalyst is a technical problem that needs to be solved for large-scale commercialization of fuel cell.Based on above bachground,four works were carried out in this thesis as followed:?1?The catalysts of Au₂Pt₁/C?Au₁Pt₁/C and Au₁Pt₂/C were obtained by chemical reduction of H₂PtCl₆ and HAuCl₄ with sodium borohydride?NaBH₄?,respectively.Three kinds of nanoparticles were characterized and analyzed by TEM,HRTEM,ICP,XRD and XPS.The results showed that the AuPt bimetallic nanoparticles are well dispersed on the carbon carrier with an average diameter of 3.40 nm.Au₂Pt₁ and Au₁Pt₂nanoparticles tended towards bimetallic structure,but Au₁Pt₁ nanoparticles possessed of alloy structure.Moreover,the surfaces of Au₂Pt₁/C,Au₁Pt₁/C and Au₁Pt₂/C nanoparticles were all Pt rich.The synthesis process showed that different atomic ratios of AuPt nanoparticlse can be obtained by adjusting the ratio of precursor.?2?The catalytic performance of the commercial Pt/C,commercial PtRu/C,Au₂Pt₁/C,Au₁Pt₁/C and Au₁Pt₂/C for methanol oxidation were studied in the experiment.Electrochemical CV and CO stripping test and durability test showed that for all studied catalysts,the order of activity is Au₂Pt₁/C>Au₁Pt₁/C>Au₁Pt₂/C>PtRu/C>Pt/C.Moreover,the CO stripping potential of Au₂Pt₁/C was the lowest.The durability test results showed that the addition of Au improves the stability of methanol oxidation.?3?Compared with commercial PtRu/C,the catalytic performances of the Au₂Pt₁/C,Au₁Pt₁/C and Au₁Pt₂/C nanoparticle catalysts for hydrogen oxidation were explored.The results of eletrochemical LSV,CV and durability test showed that the alloying Au₁Pt₁/C has the highest catalytic activity to the HOR in the alkaline environment,due to the adsorption energy of H_ad on Pt site is reduced.Moreover,Au₁Pt₁/C has an excellent durability in alkanie medium,making it a promising alternative to commercial PtRu/C.?4?Finally,the COOH group was introduced on the surface of CNTs,and then used as a catalytic carrier to support the metal Pt,PtRu and AuPt.TEM,ICP,XRD and XPS were used to comprehensively characterize the three kinds of nanoparticles on COOH-CNTs.Their catalytic methanol oxidation performance were determined by CV,LSV,CA and CO stripping experiments.The results showed that Pt,PtRu and AuPt are uniformly dispersed on the CNTs carrier.XPS results revealed that the electron of Pt will transfer to the COOH-CNTs,and electron transfer occurred in AuPt/COOH-CNTs is the most obvirous.Thus,the AuPt/COOH-CNTs catalyst has the best methanol catalytic performance,which is obviously superior to PtRu/COOH-CNTs and Pt/COOH-CNTs catalysts,as the gold has a good resistance to CO posioning.