Structural Evaluation For Catalyst Based On Cataluminescence

Catalysts are important for catalytic reaction,and their microstructure（such as specific surface area,defect sites,etc.）directly affects the catalytic reaction process and reaction efficiency.The large specific surface area of the catalyst is conducive to the dispersion of the active centers of the catalyst,thereby improving the contact between the reactants and the catalytic active sites.The large specific surface area is beneficial for promoting the adsorption and enrichment of the reactants,and accelerating the reaction process.The oxygen vacancy of the catalyst can capture oxygen from the surrounding atmosphere and convert gaseous oxygen molecules into more active oxygen,improving the catalytic ability of the catalyst and promoting the oxidation reaction.Therefore,the evaluation of the microstructure of catalysts is the basis for understanding the catalytic ability of catalysts and conducting research on structure-activity relationships.Cataluminescence（CTL）analysis has attracted widespread attention due to its advantages such as good linearity,high sensitivity,controllable selectivity,and fast response signals.In this thesis,cataluminescence was used for a rapid evaluation on the specific surface area and oxygen vacancies of catalysts.Based on the adsorption and catalytic reaction abilities of catalysts with different structures,the correlation between the cataluminescence intensity and its specific surface area or oxygen vacancies was established.This thesis has provided a new platform for rapid evaluation and screening of catalysts.The specific research results are divided into the following two parts:1 Screening specific surface area for metal-organic frameworks by cataluminescenceMetal-organic frameworks（MOFs）are crystalline coordination materials composed of inorganic nodes and organic ligands,which have high porosity and large specific surface area.In this work,we have proposed cataluminescence（CTL）strategy for an accurate and rapid screening on the surface area of MOFs,based on the adsorption-desorption and catalytic reaction of ethanol.The CTL intensities,derived from the oxidation of ethanol,differed for aluminum-based MOFs with the large-pore（lp）,narrow-pore（np）and medium-pore（mp）according to a tendency of lp>mp-150>mp-130>mp-140>np.Note that the variations of CTL intensities are highly correlated with the surface area of the MOFs,due to the distinct capacity of MOFs to accommodate and activate ethanol.The reaction mechanism of ethanol oxidation catalyzed by MOFs and the generation of chemiluminescence signals was determined by chemiluminescence spectroscopy,gas chromatography-mass spectrometry,and in situ infrared spectroscopy.Based on the correlation between the cataluminescence intensity of ethanol and the specific surface area of MOFs in different pore phases,this work achieved rapid screening of the surface area of MOFs using cataluminescence,providing new methods and ideas for structural evaluation.2 Rapid screening of oxygen vacancies in composite Zn-Fe oxides by cataluminescenceBimetal oxides refer to metal oxide materials composed of two different metals,and the formation of oxygen vacancies in them can change their catalytic performance.In this work,composite zinc iron oxides with different ratios of Zn and Fe were synthesized and used to catalyze chemiluminescence of H₂S.The correlation between the cataluminescence signal and oxygen vacancies was established,enabling rapid screening of oxygen vacancies in Zn-Fe oxides（Zn_xFe_yO_z,z=x+3y/2）.Due to the different contents of oxygen vacancies in Zn_xFe_yO_z,the cataluminescence intensities from H₂S exhibited a trend of Zn₂Fe₁O_3.5>Zn₂Fe_0.5O_2.75>Zn₂Fe_1.5O_4.25>Zn₂Fe₂O₅.The changes in cataluminescence intensity were consistent with the change trend of surface oxygen vacancies measured by XPS.The mechanism of the catalytic reaction was investigated by means of chemiluminescence spectroscopy and XPS methods.The origin of the cataluminescence was from the oxidation of H₂S to excited SO₂*and the corresponding cataluminescence when SO₂*returned to the ground state.Therefore,the correlation between the cataluminescence of H₂S and the oxygen vacancies on the surface of Zn_xFe_yO_zwas established.Accordingly,a fast screening on the oxygen vacancies of Zn_xFe_yO_zwas realized.It is anticipated that the proposed strategy could be extended to the evaluation of surface defects in other oxides or composite materials.