文献汇报ppt课件.ppt

Paper Review 李俊乾李俊乾 化学工程（专）化学工程（专） 14102932 Synthesis, characterization and electrochemical studies of nano-structured CaWO4 as platinum support for oxygen reduction reaction(纳米钨酸钙的合成、表征和其负载铂对氧还原反应的电催化纳米钨酸钙的合成、表征和其负载铂对氧还原反应的电催化)1Literature source2ContentsIntroduction 12 Experimental section1 Conclusions234Results and discussion31. Introduction In recent years, proton exchange membrane fuel cells(PEMFCs) have been recognized as promising devices for portable and transport applications due to their good energy conversion efficiency, high power density, low operating temperature, and easy transport. PEMFC’S working PEMFC’S working principle:principle:4经营者提供商品或者服务有欺诈行为的，应当按照消费者的要求增加赔偿其受到的损失，增加赔偿的金额为消费者购买商品的价款或接受服务的费用1. Introduction The cathodic reaction of oxygen reduction reaction (ORR)The anodic reaction of hydrogen oxidation reaction forH2+2M→2MH 2MH→2M+2H++2e- O2+H++M+e-→MHO2 MHO2+H++e-→MO+H2O MO+H++e-→MOH MOH+H++e-→M+H2O Electrocatalytic reaction mechanism:5经营者提供商品或者服务有欺诈行为的，应当按照消费者的要求增加赔偿其受到的损失，增加赔偿的金额为消费者购买商品的价款或接受服务的费用 In the fuel cell in the work process, the platinum catalyst active surface area will be gradually reduced, resulting in the attenuation of fuel cell performance.the properties of Pt/PtM alloy recession schematic diagram6 Experimental section272. Experimental sectionØSynthesis of nanostructured CaWO4: 80°CpH=7white precipitates were collected by centrifugation Na2WO42H2O (5 mM)CaCl26H2O (5 mM)CaWO4mixed together dried initially at room temperature calcinate500 C for 5 h 8经营者提供商品或者服务有欺诈行为的，应当按照消费者的要求增加赔偿其受到的损失，增加赔偿的金额为消费者购买商品的价款或接受服务的费用2. Experimental section•Catalyst preparation: calcium tungstate(1) Graphite(2) CaWO4/graphite electrode K2PtCl4（2.5mM）H 2 SO 4（0.25 M）the catalyst of Pt/CaWO4-graphite 30 wt.% of n-eicosane heatedelectrochemically precipitated 923Results and discussion103. Results and discussion The approximate crystallite sizes of samples were estimated by the Scherrer’s formula: The particle size and morphology of CaWO4 were examined using TEM ，D=10–25 nm. 113. Results and discussionThese reduction peaks are not symmetric because of depletion of PtCl42-ions in the vicinity of the electrodes in potentials more negative than the peak potentials .Cyclic voltammograms during electrodeposition Pt on both graphite and nano-CaWO4/graphite. 123. Results and discussion(a) and (b) Scanning electron microscopy images of Pt/CaWO4-graphite. In these pictures, brighter areas corresponded to Pt and CaWO4 that the platinum particles are dispersed over the surface of the support and graphite sheet. 133. Results and discussion(d)The EDXspectrum presence of Pt, Ca and W in thePt/CaWO4-graphite catalysts 143. Results and discussionArea indicating that electrochemical activity. Cyclic voltammograms of CaWO4-graphite, graphite, Pt/CaWO4-graphite and Pt/graphite in a 0.5 M H2SO4 aqueous solution at scan rate of 50 mV/s. The size of the oxidation and reduction current depends on the value of Pt-dispersion.153. Results and discussion返回返回 The oxygen reduction peak current increases linearly with the square root of scan rate, emphasizing on the controlling of the reaction by oxygen diffusion to the electrode surface Cyclic voltammograms of the Pt/CaWO4-graphite in a 0.5 M H2SO4 at various scan rates.163. Results and discussion The more positive half wave potential indicates the enhanced electroc-atalytic activity of the catalysts for ORR . Linear sweeping voltammograms of Pt/CaWO4-graphite and Pt/graphite in O2 saturated 0.5 M H2SO4 solution with a scan rate of 25 mV/s.173. Results and discussionIt is clear that the Pt/CaWO4-graphite shows a lower charge-transfer resistance due to the smaller semicircle’s diameter compared to Pt/graphite catalyst in 0.5 M H2SO4 solution.Nyquist plot for Pt/CaWO4-graphite and Pt/graphite in 0.5 M H2SO4 vs. Ag/ AgCl.18 Conclusions4194. conclusionsØ Nano-structured calcium tungstate was synthesized by the co-precipitation .Ø The application of CaWO4 as a catalyst support for Pt. Ø Pt/CaWO4-graphite catalyst exhibited better electrochemical activity for oxygen reduction reaction in H2SO4 solutio compared to Pt/graphite. 20Thank you for your attention!21。