Study On The Structure-Function Relationship Of CO Oxidation Or Water Gas Shift Reaction Catalyzed By Gold Or Platinum Supported With Titanium Dioxide

CO is a common toxic gas,widely exists in the atmosphere and some industrial production process,so it’s a direction of people’s long-term efforts that find an effective way to eliminate CO.CO oxidation reaction and water gas shift reaction play important roles in the elimination of small amount of CO.In many developed catalyst systems,the noble metal catalysts supported by oxides generally show excellent catalytic performance.For CO catalytic oxidation,supported Au catalysts have been attracting much attention.However,there are still some controversial points on the determination of active species,the contribution of support to catalytic activity and reaction mechanism,which are of value for further exploration.For water gas shift reaction,supported Pt catalyst have been reported by many researchers because of its high catalytic activity and good stability at low temperature.Such catalytic systems also face challenges and opportunities in exploring the influence of the performance of the support on the state of the metal and catalytic properties.Therefore,in this paper,the classical functional material TiO₂ was selected as the support of the supported noble metal（Au or Pt）catalysts,and the modification of the support was committed to the method of post-processing or direct synthesis.While obtaining highly active catalysts,the structure-function relationship of catalysts in CO oxidation or water gas shift reaction were explored by means of a series of characterization technologies and research methods,highlighting the importance of catalyst support in heterogeneous catalytic systems.This paper mainly completes the following work:1.The effect of hydrogenated TiO₂ to the Au/TiO₂ catalyst in catalyzing CO oxidationSupported Au catalysts are widely used for CO oxidation due to extremely high activity,and the modification of support structure is a crucial method to improve catalytic performance.Herein,we prepared gold catalysts supported on flaky TiO₂ and on TiO₂ hydrogenated at different temperatures（200,400,and 600℃）.We found that the sample with the support pretreated in hydrogen at 600℃（0.5Au/TiO₂-H600）showed greatest advantages in activity and stability over the sample with as-prepared TiO₂ nanosheets（0.5Au/TiO₂-UC）.Firstly,calcination at 600℃ changed the exposing surface of TiO₂ from {001} to {101},and gold nanoparticles（2-3 nm）were observed as highly reactive species on 0.5Au/TiO₂-H600.Moreover,the increase of oxygen vacancies on the surface of 0.5Au/TiO₂-H600 was conducive to oxygen activation and promoted the catalytic activity.Therefore,we emphasized the important role of the support and gave an effective method to improve the catalytic performance by regulating the support structure.2.Study on the catalytic performance of CeO₂-TiO₂ composite supported with Pt for water gas shift reactionWater gas shift（WGS）reaction is a very important step in the industrial hydrogen production and the development of proton exchange membrane fuel cell.A lot of studies have proved that supported Pt catalyst is an important research system due to its excellent performance in WGS reaction.A series of supported Pt catalysts 0.5Pt/xCe-10Ti（x=1,3,or 5）with different Ce:Ti molar ratios were successfully prepared by depositing CeO₂ nanoparticles on TiO₂ nanosheets by a simple deposition-precipitation method.Compared with pure TiO₂ and CeO₂ supported Pt catalysts,it was found that 0.5Pt/3Ce-10Ti sample showed obvious activity advantage in WGS reaction.The high activity of the catalyst was attributed to two aspects:On the one hand,when using CeO₂ modified TiO₂ support,the reduction of the supported Pt catalyst was improved.On the other hand,the adsorption strength of CO on the surface of 0.5Pt/3Ce-10Ti was more moderate due to the regulation of Pt state by CeO₂-TiO₂.A large number of Pt single atoms connected with CeO₂ were considered as the main active sites.Finally,it was preliminarily confirmed that 0.5Pt/3Ce-10Ti and 0.5Pt/CeO₂ had similar association mechanism,and 0.5Pt/TiO₂ may followed the redox reaction mechanism.This work shows that the mixed bimetallic oxide support has the advantage of performance in WGS reaction,and provides a reference for the development and application of composite materials in heterogeneous catalysis.