Preparation Of Platinum-based Catalyst And Their Electrocatalytic Performance

At present,social and economic development is highly dependent on energy supply.Environmental pollution is becoming more and more serious.Non-renewable energy is becoming scarcer and the demand for energy is increasing day by day.However,the reality is that there is an insurmountable gulf in energy and it has become a hamper of human development in the 21st century.Therefore,the development of a highly efficient,safe,green and pollution-free renewable energy source has become a key point of sustainable social and economic development.Proton Exchange Membrane Fuel Cell?PEMFCs?has received wide attention due to its environmental friendliness and its advantages as a renewable energy source.However,the current electrode catalysts of PEMFCs are still mainly based on platinum-based materials.However,platinum has a small amount of reserves on the earth and is expensive,so it has largely hindered the commercialization process in PEMFCs.Therefore,in order to ensure the high activity of the catalyst and reduce the production cost,the PEMFCs can be widely promoted and applied.This topic is mainly to prepare a series of sandwich-like Co@Pt/C catalysts with different Pt thickness and Pt nanoparticle supported on hollow porous VN composites by means of morphology control and surface modification.Combining existing test methods,the composition,morphology,chemical state and electrochemical properties of the prepared materials were investigated.The electrochemical performance analysis showed that the sandwich-like Co@Pt/C core-shell catalyst with suitable Pt thickness can exhibit good oxygen reduction performance and good corrosion resistance in acidic electrolytes.Similarly,the Pt nanoparticle supported on the hollow porous VN composites also exhibit superior electrocatalytic performance than pure VN,due to the interaction between the supported Pt nanoparticles and the hollow porous VN of the support material.The specific research contents of this topic are as follows:1?By two hydrothermal reactions,the intermediate product was prepared,which is obtained polymerizing the precursor with the help of the clean carbon source glucose.Then,the polymer-forming product was subjected to high-temperature anneal treatment to prepare a sandwich-like carbon film coated metal Co nanoparticle.Finally,the metal displacement reaction was carried out between a suitable concentration of H₂PtCl₆solution and sandwich metal Co nanoparticles.Pt atoms were deposited on the edge of Co nanoparticles by epitaxial growth,thus successfully preparing a series of Co-Pt core-shell catalyst with different thicknesses Pt layers.By analyzing the transmission electron microscopy data of high angle annular dark field scanning and X-ray diffraction data,we found that the lattice spacing of the outer Pt shell of the sandwich Co@Pt/C core-shell catalyst is smaller than the corresponding lattice spacing of the standard card.At the same time,the binding energy of Pt 4f is positively shifted in the X-ray photoelectron spectroscopy data.It can be seen that the reason for the above two results is that the inner layer of the Co nucleus forms a compressive strain on the outer layer Pt.Thus,it contributes to the improvement in catalytic activity and stability of the sandwich-like Co@Pt/C core-shell catalyst for the oxygen reduction reaction.2?Two-dimensional Zn₃?OH?₂?V₂O₇??H₂O?₂nanosheet were prepared by hydrothermal method,and then hollow porous VN base materials were prepared by calcining the precursor in an atmosphere of NH₃ and Ar gas with ratio of 3:1.After mixing with VN and H₂PtCl₆ solution under stirring,the newly NaBH4 solution was added to reduce Pt⁴⁺ions to form Pt nanoparticles.Finally,a Pt nanoparticles supported on a hollow porous VN composite was prepared.By characterizing it with high-angle annular dark-field scanning transmission electron microscope,we can clearly observe that VN exhibits a porous hollow structure and supports Pt nanoparticles.Because VN has hollow porous structure,it can provide a large active surface area and VN itself has Pt-like properties,which has a certain catalytic effect on oxygen reduction reaction and forms a co-catalytic effect with Pt nanoparticles.Therefore,Pt nanoparticles supported on VN catalyst.It exhibits excellent oxygen reduction catalytic activity and structural stability.This experiment focuses on reducing the amount of Pt precious metals,reducing the preparation cost and improving the catalytic activity and stability of the oxygen reduction reaction.