Synthesis And Electrocatalytic Properties Of Pt - Based Nanostructures With Different Dimensions By Iodine Ion Regulation

Proton exchange membrane fuel cell (PEMFC) is considered most likely to replace the power source of the internal combustion engine in the field of transportation and applied to the mobile or fixed power supply. Although this type of fuel cell has been successfully applied to the power source of the electric car and computers, mobile phones and other mobile power supply, but also exist some problems such as the high cost, catalytic performance, service life and hydrogen source hinder the realization of industrialization. At present, the proton exchange membrane fuel cell electric catalyst has the following main problems yet to be resolved:(1) be sensitive to CO; (2) the lower methanol oxidation and oxygen reduction reaction kinetics; (3) noble metal is essential; (4) accelerate durability. So far, due to the electronic effect, synergy effect and facet effect, Pt nanomaterials with a particular morphology has been recived widely attention. But, how to control the platinum catalyst size in the process of synthesis, keep the nanoparticle surface clean and control the surface structure of the alloy nanoparticles in synthesis, are still to solved. This thesis embarks from the one step hydrothermal method, research on the use of iodine ion in combination with other green table activator on the Pt base matal in controling the synthesis of nanomaterials. We also study the catalysts catalytic performance in the oxygen reduction reaction and formic acid oxidation catalysis.The main results and conclusions are summarized as follows:1. We synthesized the o dimension interconnected porous sphere (Pt-IPNSs) by using the green compoound and inorganic ions to regulate the surfaca controling. The obtained Pt-IPNSs were first inspected by TEM and SEM. The Pt-IPNSs were interconnected and porous nanosphere structure. The condition control experimentals confirm the nanostructure was the combined action of PAH (Polyallylamine hydrochloride) and iodide ions. The porous structure of the Pt-IPNSs makes it has larger specific surface area, the more step atomics and the more active sites. All of these feztures may make for the excellent catalytic performance to formic acid oxidation. It is noteworthy that the ration of oxidation of formic acid via the dehydrogenation pathway increases and it has excellent anti-CO performance. This may ascribe to the following:(i) the unique porous structure allows the target molecules facile access to the Pt active sites; (ii) the combination of porous features and anisotropic 3D morphology may be inherently beneficial for electron and mass transport during FAOR, thus may result in the highly enhanced catalytic activity of the Pt-IPNSs.2. Due to the electronic effect and synergy effect, the electrocatalytic performance of the synthesized alloy will be improved as the adding of another matal. In the coefficient of segmented copolymer F127 and iodide ions, we successfuly prepared one dimmension ultrathin wavy PdPt nanowires. Grain boundaries are clearly observable between the varied oriented grains along the nanowires. The emergence of grain boundaries and rich edges could effectively enhance the electrocatalytic activity.3. Wet chemical method tends to utilize the surfatant to control the morgraphy, and to inhibit the agglomeration of particles. But, the surfactant with the adsorption alwanys occupied the active sites, and this lower the catalytic perfoemance of nanometarials. So, in this work, we developed a one route hydrothermal synthesis without any surfactant and templates to syntheses three dimension coral-like Pt nanochains (Pt-3DCNCs). Under the regualting of iodide ions, we obtained the coral-like platinum nanochains. They interconnect with each other forming large extended nanochains. The as-prepared Pt nanostructures are nanochain networks with secondary pores 10-50 run, which can enlarge the contact region between the catalysts and the electrolyte soution. These can improve the ORR catalytic performance. The Pt-3DCNCs also has excellebt stability due to its self-supported structure. After the accelarated stability tests, it keep the original structure.There are two main reasons ascribing to the special structure:(1) the addition of Γ decrease the reduction potential of Pt (Ⅱ) ions due to the formation of a more stable coordinated anion [PtI4]2-, allowing the kinetics controlled synthesis; (2) The adsorption of Γ on Pt surface facilitates the growth of Pt{111} facets during the synthesis of the nanostructure.