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Ceramics International

journal homepage:www.elsevier.com/locate/ceramint

Reversible redoxbehavior ofFe

2 O 3 /TiO 2 composites inthe gaseous photodegradation process

Xueping Dai

a b,1 , GuanhongLu a 1 , YidanHu a , XiaofengXie a , XiaoWang a , JingSun a ??a Shanghai Instituteof Ceramics,Chinese Academyof Sciences,1295 DingxiRoad, Shanghai,200050, China b University ofChinese Academyof Sciences,19 (A)Yuquan Road,Beijing, 100049,China

ARTICLEINF O

Keywords:

Photocatalysis

Redox behavior

Fe 2 O 3 /TiO 2

VOCs removal

Regeneration

ABSTRACT

The useof photocatalytictechnology inVOCs pollutantsremoval hascaused greatattention. Fe 2 O 3 possesses

some uniqueadvantages amongdiverse visible-lightdriven photocatalystsdue toits narrowbandgap, abundant

reserves andfavorable biosafety.In thiswork, Fe 2 O 3 /TiO 2 composites wasfabricated bya facileimpregnation method andtheir photocatalyticperformance towardsacetaldehyde ando-xylene wasdetected. TEM,EDS, photoluminescence spectraand UV-Viswere usedto characterizethe morphologyand propertiesof theFe 2 O 3 TiO 2 composites. Itwas provedthat thephotocatalytic abilityof TiO 2 was greatlyimproved bycoupling with Fe 2 O 3 . Interestingly,the Fe 2 O 3 /TiO 2 composites showeddeactivation inthe degradationof acetaldehydewhile no suchphenomenon inthe o-xylenecase. Thereason couldbe thatFe 3+ accepted thephoto-induced electrons of TiO 2 and wasreduced toFe 2+ , whichcan easilycombine withthe intermediateproduct ofacetaldehyde and generated Fe(CH 3 COO) 2 . Moreover,the deactivatedphotocatalyst canbe regeneratedby heattreatment, since

Fe(CH3

COO) 2 can bedecomposed intoFe 2 O 3 in air.ESR wasfurther usedto demonstratethis mechanism.This

work revealsthe coupledredox reactionsin thephotocatalytic process,which isbene fit forthe designof new

photocatalysts.

1. Introduction

Volatile organiccompounds (VOCs),as commonpollutants inthe air, haveattracted greatattention recently,mainly becauseof their potential tocause somehealth problems[ 1-6]. Amongthe airpur- ification methods,photocatalytic oxidationprocess hasbeen widely studied aboutits applicationsdue toits non-toxic,broad-spectrum and longevity ofservice [7-10]. TiO 2 is generallyused asa semiconductor photocatalyst becauseit isphysicochemical stable,non-toxic, low-cost and withexcellent photocatalyticactivity underultraviolet irradiation [11]. However,TiO 2 has lowlight responserange andhigh photo- electron holerecombination rate,which limitsits applicationin pho- tocatalysis [12-17]. Manystudies havefocused onsolving thetwo disadvantages ofTiO 2 , suchas constructingheterostructure with narrow bandgap semiconductor[ 18-21]. Fe 2 O 3 is currentlyconsidered as oneof themost promisingsemiconductor materialsfor photo- catalytic processdue toa seriesof desirableproperties, includingade- quate absorptionfrom visiblelight regionin solarspectrum (bandgapis about 2.3eV),excellent stabilityin theair, andearth-abundant [22-24].Therefore, Fe 2O 3 modified TiO 2 heterojunction compositeshave been widelyreported. Forinstance, AlirezaBanisharif etal. synthesized Fe 2 O 3 -TiO 2 by anultrasonic-assisted coprecipitationmethod andused it to degrade500 ppmtrichloroethylene (TCE)in air[ 25]. Amarjargal et al.prepared TiO 2 decoratedα-Fe 2 O 3 microflowers heterostructure, which obtainedmuch betterphotocatalytic efficiency about92% to- wards Methylblue (MB)degradation after80 minunder visiblelight irradiation [26]. HuaTang etal. synthesizedthe novelα-Fe 2 O 3 /TiO

2composite hollowspheres, whichshowed anexcellent performancein the photocatalyticdegradation ofRhodamine B(RhB) inaqueous so-

lution undervisible light[ 27]. AlthoughFe 2 O 3 modification hasbeen widely demonstratedto effectively improvevisible lightresponse of catalysts, thephotocatalytic processis stillunclear. Accordingto some reports, themechanism ofpromoting theseparation ofphoto-induced electron holepairs ismainly dueto thatFe 3+ was reducedto Fe 2+ by trapping electrons.However, thishypothesis isdevoid ofdirect ex- perimental evidence.Electron spinresonance (ESR)is amagnetic re- sonance techniquethat generatesmagnetic momentsof unpairedelec- trons, whichcan beused toqualitatively andquantitatively detectthe Received 23March 2019;Received inrevised form31 March2019; Accepted31 March2019 ?

Corresponding author.

Corresponding author.

E-mail addresses:xxfshcn@163.com(X. Xie),jingsun@mail.sic.ac.cn(J. Sun). 1 Xueping Daiand GuanhongLu contributedequally tothis work. $YDLODEOHRQOLQH$SULO quotesdbs_dbs44.pdfusesText_44

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