The Support Effect Study On Iron-based Oxide Supported Pt Catalysts For Low-temperature CO Oxidation

CO catalytic oxidation is a reaction with important application background,which attracts extensive attention in air cleaning,gas purification,etc.It could also be used as a representative probe reaction to understand and explain the basic problems in heterogeneous catalysis,which has brought intense attention of scientific researcher.In low-temperature CO catalytic oxidation,following the Au catalysts exhibit excellent low-temperature activity,supported Pt catalysts can also achieve CO oxidation in low-temperature.The activity and stability of Pt catalyst can be affected by Pt particle size,support redox properties and interaction with active center,etc.Finding out the impact of these factors is very important to the rational design of Pt catalysts.Colloid method was used to control Pt nanoparticle size for preparing Pt/Fe Ox catalysts previously.Based on that,this paper tries to understand the support role in constructing highly efficient active center.The impact of Fe Ox structure and surface property in constructing Pt active center and CO oxidation process were investigated in detail.The role of Fe Ox surface hydroxide group in catalyst preparation and CO reaction was disclosed.For Fe Ox support stability problem in the process of long-term use,MgFe₂O₄ with inverse spinel structure and modified La Fe O3 with perovskite structure were adopted to prepare highly efficient and stable Pt catalysts.The role of support in constructing catalyst and reaction was further studied.The main contents and results are as follows:1.Role of Fe Ox support microstructure in constructing high performance Pt/Fe Ox catalyst Based on a simple colloid deposition method,a series of Pt/Fe Ox catalysts were prepared using 3-4 nm Pt colloid nanoparticles and Fe Ox with different microstructure?i.e.the structure and surface properties?.Fe Ox support was obtained via a thermal-treatment method,which enables the tailoring of Fe Ox from ferrihydrite to ?-Fe2O3 and the amount of hydroxides on the surface of Fe Ox decreases gradually with the phase changing.Over anoptimized Pt/Fe Ox,CO could be completely converted at room temperature?298 K?at a relatively high space velocity?1.2×105 m L·g-1·h-1?.The correlation between the microstructure of Fe Ox support and the CO oxidation performance of resultant Pt/Fe Ox catalyst was investigated.Although the oxidation of Pt nanoparticles is inevitable in the process of Pt-loading,relatively large amounts of Pt0 species can be preserved on the Fe Ox support with abundant surface hydroxides.In-situ DRIFT shows that the surface hydroxides of Fe Ox could participate in the catalytic process: they could react with CO absorbed on Pt0 sites and then recover easily in the co-presence of molecular oxygen and water gas.These results show that intrinsic properties of Fe Ox support not only affect the oxidation state of supported Pt nanoparticles in the preparation process,but also provide new active sites in the catalytic process.Fe Ox support possessing abundant surface hydroxides is suitable for preparing high performance Pt/Fe Ox catalyst for low-temperature CO oxidation.2.MgFe₂O₄ with inverse spinel structure for preparing highly efficient and stable Pt/MgFe₂O₄ catalyst According to above work,for improving the stability of Pt catalyst,MgFe₂O₄ with better stability was introduced as support.MgFe₂O₄ support with inverse spinel structure was developed through tailoring preparation method.This MgFe₂O₄ support possesses good stability and abundant surface under-coordinated lattice oxygens.The Pt/MgFe₂O₄ catalyst prepared with MgFe₂O₄ support exhibited high activity and stability for room-temperature CO oxidation in the presence of water vapor.The excellent performance of Pt/MgFe₂O₄ attributes to the presence of large amount of under-coordinated lattice oxygens on the surface of MgFe₂O₄ support,which could participate in the initial CO oxidation.These active oxygen species could be recover in the presence of molecular oxygen.The inverse spinel structure of MgFe₂O₄ support and Pt/MgFe₂O₄ catalyst may be benefit for the activation and dissociation of O-O band.3.Lanthanum ferrite with perovskite structure supported Pt catalyst for CO oxidation In this work,we introduced perovskite oxides?ABO3?,whose structure and surface properties could be adjusted,into the catalyst system.The perovskite oxides were prepared by changing the molar ratio of La and Fe,which were used as supports for preparing Pt catalysts.In La Fe2 Ox oxide,the abundant Fe species restricted the growth of La Fe O3 andformed iron-based oxide.Relative to La Fe O3,La Fe2 Ox possesses bigger BET surface area and abundant surface oxygen species.After loaded Pt nanoparticles,the BET surface area and surface oxygen species amount were almost the same.The Pt/La Fe2 Ox catalysts exhibit high activity and stability for room-temperature CO oxidation in the presence of water vapor.The support abundant surface oxygen species are the reason for the high performance of Pt/La Fe2 Ox catalyst.In-situ DRIFT shows CO can react with oxygen from La Fe2 Ox support,and forming carbonate species.The formed carbonate species hinder the Pt/La Fe2 Ox performance.In ambient environment,CO can react with H2 O and O2 to form bicarbonate species,which are easy to decompose.The participation of H2 O changes the reaction process,which makes Pt/La Fe2 Ox catalyst with more practical application value.