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ARTICLEAn Apparatus for Investigating the Kinetics of Plasmonic CatalysisWenZhanga,b,YongZhoua*,WeiChenb,c,TianjunWangb,ZhaoxianQinb,GaoLib,ZefengRenb,XuemingYangb,ChuanyaoZhoub,c*a.Anhui Key Laboratory of Optoelectric Materials Science and Technology,Department of Physics,An-hui Normal University,Wuhu 241000,Chinab.State Key Laboratory of Molecular Reaction Dynamics,State Key Laboratory of Catalysis,Dalian Insti-tute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Chinac.University of Chinese Academy of Sciences,Beijing 100049,China(Dated:Received on November 2,2022;Accepted on December 9,2022)Plasmonic catalysis,which is driven bythe localized surfaceplasmon resonanceof metal nanoparti-cles,has become anemerging field inheterogeneous catal-ysis.The microscop-ic mechanism of thiskind of reaction,however,remains controversial partly because of the inaccuracy of tempera-ture measurement and the ambiguity of reagent adsorption state.In order to investigate thekinetics of plasmonic catalysis,an online mass spectrometer-based apparatus has been built inour laboratory,with emphases on dealing with temperature measurement and adsorptionstate identification issues.Given the temperature inhomogeneity in the catalyst bed,threethermocouples are installed compared with the conventional design with only one.Such amultiple-point temperature measuring technique enables the quantitative calculation ofequivalent temperature and thermal reaction contribution of the catalysts.Temperature-pro-grammed desorption is incorporated into the apparatus,which helps to identify the adsorp-tion state of reagents.The capabilities of the improved apparatus have been demonstrated bystudying the kinetics of a model plasmon-induced catalytic reaction,i.e.,H2+D2HD overAu/TiO2.Dissociative adsorption of molecular hydrogen at Au/TiO2 interface and non-ther-mal contribution to HD production have been confirmed.Key words:Plasmonic catalysis,Reaction apparatus,Reaction mechanism,Driving force,Multiple-point temperature measureing,Adsorption state identificationI.INTRODUCTIONMetal nanoparticle catalysts are widely used in thefield of thermal catalysis,including scientific research13 and industrial applications 4,5.In the past tenyears,localized surface plasmon resonance(LSPR)ofmetal nanoparticles(NPs)has been introduced intoheterogeneous catalysis,and a new field,called plas-monic catalysis,has emerged 6,7.LSPR is the collec-tive oscillation of electrons in metal or dielectric materi-als interacting with external electromagnetic waves 8.The relaxation of LSPR generates hot electrons in tens Part of the special topic of the Chinese Chemical Societys 17thNational Chemical Dynamics Symposium”*Authors to whom correspondence should be addressed.E-mail:,CHINESE JOURNAL OF CHEMICAL PHYSICSVOLUME 36,NUMBER 3JUNE 27,2023DOI:10.1063/1674-0068/cjcp2211160249 2023 Chinese Physical Societyof femtoseconds and excited phonons in a few picosec-onds timescale 9.From the energy point of view,elec-trons and phonons are possible driving force in plas-monic catalysis,which is the reason why controversyexists in this field.Generally,hot electrons are proposed to inducechemical reactions on metal nanoparticle surfaces by in-jecting into the lowest unoccupied molecular orbitals(LUMO)of adsorbates in plasmonic catalysis 10,11.Such a mechanism makes plasmonic catalysis a promis-ing method to selectively control the reaction pathwaysby designing nanostructures to meet the specific chargetransfer requirements 10.This is advantageous overthermal catalysis where energies are transferred to allpossible reaction coordinates,triggering desired and un-desired reactions at the same time.The hot electron transfer mechanism is proposedmainly according to the following phenomena 1215:enhancement of the product yield or even opening ofnew reaction channels by light illumination;correlationof the product yield with LSPR absorption.Ascribingthe typical several times enhancement of the productyield to hot electron transfer,however,has been com-mented from the temperature point of view 1618.Forthe thermal reaction,the reaction rate k follows the Ar-rhenius equation:k=Aexp(EaRT)(1)where A,Ea,R and T stand for prefactor,activation en-ergy,ideal gas constant,and temperature,respectively.Due to the exponential dependence of k on the recipro-cal of T,it is critical to guarantee the accuracy of tem-perature measurement in order to compare the reactionrate quantitatively.Assuming an activation energy of 1eV,then a 50 K temperature deviation(this value istypical as measured in the results section)around 300 Kwill cause a 7-fold difference in the reaction rate.Suchdifference is comparable with those reported previouslywhich are relied on to draw the conclusion of hot elec-tron-induced reaction 13.Therefore,related work hasbeen questioned and the product yield differences aretotally attributed to the inaccuracy of temperaturemeasurement 17.This attribution,however,is alsodoubtful becau