산소환원반응활성을향상시키기위한메조기공구조를갖는ZIF기반촉매의제조방안

Abstract

Zeoliticimidazolateframework(ZIF)hasbeenregardedasthepromisingprecursorforthetransition-metal-basedelectrocatalystsforoxygenreductionreaction(ORR)inenergyconversionsystems.However,ZIF-derivedelectrocatalystshaveanintrinsicmicroporestructureresultingfromthestructureofZIFprecursors.ThismicroporestructurecaninduceadecreaseinORRcatalyticperformancebyincreasingthemasstransportresistance.Herein,wereportthesimplestrategyforadjustingthemicroporesofZIF-derivedcatalystsintomesoporesbythermaloxidationtreatmentofZn,Co-ZIFprecursors.ThemesoporevolumeandexternalsurfaceareaoftheZIF-derivedcatalyst,whichistreatedwiththermaloxidationbeforecarbonization,are3timeshigherand1.5timeshigherthanthatofthecatalystwithoutoxidationpre-treatment.TheincreasedmesoporevolumegreatlyaffectstheORRcatalyticactivitybyfacilitatingthetransportofreagentsfromthebulkelectrolytetotheactivesites.Furthermore,itselectrochemicalperformancesurpassesthatofcommercialPt/C,includingbetterkineticperformances,higherlimitingcurrentdensities,andbetterlong-termstability.|ZIF(Zeoliticimidazolateframework)와같은금속유기골격체로부터유도된비-희귀금속기반의소재는산소환원반응(ORR)전기화학촉매로써상당히유망한소재로각광받고있다.하지만,ZIF로부터유도된촉매가갖고있는내재된마이크로기공구조특성은반응물의활성점으로의확산을저해시켜물질전달저항을증가시키며ORR질량활성을감소시키는원인으로작용한다.따라서,본연구에서는ZIF로부터유도된촉매의마이크로기공특성메조기공으로확장시키는간단한구조개질방안을개발하였다.탄화공정전에간단한공기중열처리를통해탄화후ZIF로부터유도된촉매가갖는마이크로기공이메조기공으로확장됨을확인했다.적절한온도에서공기중열처리를거친후탄화된촉매가전처리를거치지않고탄화된촉매보다1.5배더큰외부표면적및3배더큰메조기공부피를보였다.적절한온도에서전처리를거치면증가된메조기공부피로인해물질전달저항이줄어드는것을EIS를통해확인했고,따라서전처리를거치지않은촉매보다우수한반파전위및4.7배높은질량활성을나타냄을RDE를활용한전기화학특성평가를통해확인했다.또한,기존의상용화된Pt/C보다도우수한개시전위,반파전위,더작은Tafelslope,더높은질량활성그리고더우수한안정성등촉매성능을나타냈다.결과적으로,본연구에서는촉매로써잠재성이큰ZIF로부터기반된촉매의물질전달저항을야기하는마이크로기공구조를개질할수있는간단하고새로운전략을제시하였다.