Effect Of Catalytic Oxidation Of Toluene Over Pt/CeO₂ With Tunning Oxygen Vacancy

Volatile organic compounds（VOCs）are important precursors of smog and ozone pollution,seriously affecting the human living environment.Catalytic combustion has been widely used for its advantages of high removal efficiency,strong impact resistance,and no secondary pollution.The key to improving this technology is to develop low-temperature and high-efficiency catalysts.Rare earth oxide ceria（CeO₂）has excellent oxygen storage and release properties,which can provide active oxygen for reactions,effectively anchor noble metal particles,and improve the thermal stability of noble metals.Due to the abundant oxygen vacancies,Pt/CeO₂catalyst systems are widely utilized in VOCs catalytic degradation reactions,but there are few studies aimed at effectively increasing the concentration of oxygen vacancies and analysing the essence of strong metal-support interaction（MSI）.Based on above question,this paper conducts the following research using Pt/CeO₂catalytic degradation of toluene as the research system:Firstly,difference oxygen vacancy concentration caused by the lattice shrinkage/expansion of CeO₂doped with Ln series elements,the influence of oxygen vacancy concentration on the chemical state of Pt is analyzed,and the obvious doping effect of Ln series elements is revealed;Secondly,by changing the amount of NaBH₄added to adjust the oxygen vacancy concentration of CeO₂,the effect of oxygen vacancy concentration on the metal-support interaction is clarified,and the structure-activity relationship of the catalyst is elucidated.The principal research contents and conclusions are as follows:（1）Pt/CeLnO_xcatalysts（Ln:La,Nd,Sm,Pr,and Gd,with 20%Ln doping and 0.6%Pt loading）are prepared by hydrothermal synthesis and impregnation methods.The characterization results of Raman,XPS,N₂adsorption-desorption,OSC testing and CO-DRIFT indicate that the Pt/Ce Gd O_xcatalyst contains the highest concentration of oxygen vacancies and Pt⁰,and the metal-support interaction is strong,exhibiting the best catalytic degradation performance for toluene.Due to the high ionic radius and the presence of+4 valence state of Pr element,its doping is not conducive to the formation of oxygen vacancies,the metal-support interaction is weak,the low Pt electron density has weak adsorption and dissociation ability for toluene,and the catalytic degradation of toluene is poor.Therefore,for the Pt/CeO₂catalytic degradation of toluene system,the introduction of low valence elements with small ionic radius will enhance the metal-support interaction,and improve the catalytic activity of the catalyst.（2）Pt/CeO₂-X catalysts with different oxygen vacancy concentrations are prepared by hydrothermal synthesis and NaBH₄reduction methods（the mass ratios of X:NaBH₄to CeO₂were 0.25,0.5,and 1.0 respectively,with Pt loading of 1.0%）.EPR,Raman,XPS and DFT calculations results show that with the increase of reduction ratio,the oxygen vacancy concentration of CeO₂increases,the Pt with low coordination number and its electron density increase,the metal-support interaction becomes stronger.Through HRTEM,it is found that as the metal-support interaction increasing,the degree of encapsulation of Pt NPs by CeO₂increasing,resulting in a decrease in the surface area and reaction sites exposed to the metal.The TOF values are calculated based on the content of Pt⁰species and dispersion respectively,and the key factors of Pt/CeO₂catalytic oxidation of toluene in the strong metal-support interaction were identified.