Creation Of Loaded Copper-cerium Catalysts And Platinum Rare-earth Alloy Catalysts And Their Application To CO-PROX

Proton exchange membrane fuel cell（PEMFC）has become an ideal way to utilize hydrogen energy as an efficient energy conversion device with portable,high capacity efficiency and moderate cost with the continuous improvement of hydrogen energy industry chain.However,hydrogen obtained from hydrocarbon reforming still contains traces of CO（~1%）after the water gas conversion reaction,which can poison the Pt electrode of the fuel cell.The CO preferential oxidation（CO-PROX）reaction in a hydrogen-rich atmosphere is the most effective method to remove CO in PEMFC.In this field of research,copper-cerium（CuxO/CeO₂）catalysts and platinum-rare earth（Pt-REE）catalysts are of interest because they possess better low-temperature activity.However,the development of both catalysts faces the challenges of simultaneously controlling the rich active sites and interfacial reduction of CuxO/CeO₂ catalysts on the one hand,and taking full advantage of the unique electronic structures of Pt and rare earth elements to enable them to exhibit high catalytic activity in the CO-PROX reaction on the other.Based on this,this thesis focuses on the following studies and explorations to modulate the properties of CuxO/CeO₂ catalysts using surfactants,reducing agents and O₂/H₂ pretreatment,as well as alloying Pt with rare earth elements to adjust the metal electronic structure and explore its catalytic performance in the COPROX reaction.The details of the study are as follows:1.The CuxO/CeO₂ catalyst was synthesized by a hydrothermal method,and the porosity,active sites and oxygen vacancy sites（OV）of the CuxO/CeO₂ catalyst were tuned by reducing media and O₂/H₂ activation.O₂-pretreated CeO₂-supported Cu catalysts unequivocally demonstrate the low-temperature activity owing to the abundant Cu+ and Cu2+ concentration as well as the relative population of Ce³⁺ and Ovacancy sites at the surface.O₂ activation improves the Cu²⁺ diffusion into the CeO₂ lattice to generate the synergistic effect and induces the formation of electron-enriched Cu²⁺-OV-Ce³⁺ sites,which accelerate the activation and dissociation of CO/O₂ and the formation of reactive oxygen species during catalysis.Density function theory（DFT）calculations reveal that CO adsorbs on Cu₂ O {110} and CuO {111} with relatively optimal adsorption energy and longer C-Cu lengths in contrast to that on Cu {111},favoring the adsorption and desorption of CO.These are crucial for ongoing CO oxidation,producing CO₂ by the Mars-van Krevelen mechanism.2.The SiO₂ carriers possessing Si-OH（silanol nest）on the surface were prepared by different methods using Na₂SiO₃ and TEOS as silicon sources,while the carriers were later modified using 3-aminopropyltriethoxysilane（ATPES）as a silane coupling agent.Pt Ce,Pt Y and Pt La alloys were formed on the surface of the carriers by primary wet impregnation.It was observed that the nanoalloy particles were distributed on the catalyst surface in smaller sizes（~2.67 nm）by characterization such as high-angle annular dark-field scanning transmission election microscope.Special aberration corrected transmission electron microscope reveals that the growth of Pt5 Ce alloys along（111）,（110）and（101）directions,respectively.IR combined with XRD and XPS characterization revealed that silanol nests enhanced the chemical potential of rareearth elements through coordination effects and promoted electron transfer between Pt and rare-earth elements,which in turn formed intermetallic alloy compounds with ordered atomic arrangements.The modification of SiO₂ support by amination further improves the coordination between metal-carrier,thus inhibiting the atomic agglomeration of Pt and rare earth elements,resulting in a significant increase in alloy dispersion.Activity tests showed that the 1% Pt Ce/NH2-SiO₂ catalyst had the best activity,which was attributed to the strong active substance-carrier interaction promp ting the presence of rare earth alloys in smaller sizes,exposing more active sites,and the alloying of Pt with rare earth elements facilitated the adsorption and oxidation of CO,significantly improving the catalyst activity.