Exfoliated 2D MAX Ti3AlC2 conductive cocatalyst anchored with g-C3N4/TiO2 to construct 2D/0D/2D het-erojunction has been explored for enhanced CO2 photoreduction in a fixed-bed and monolith photoreac-tor.The TiO2 particle sizes(NPs and MPs)were systematically investigated to determine effective metal-support interaction with faster charge carrier separation among the composite materials.When TiO2 NPs were anchored with 2D Ti3AlC2 MAX structure,10.44 folds higher CH4 production was observed com-pared to anchoring TiO2 MPs.Maximum CH4 yield rate of 2103.5 μmol g-1 h-1 achieved at selectivity 96.59％using ternary g-C3N4/TiO2/Ti3AlC2 2D/OD/2D composite which is 2.73 and 7.45 folds higher than using binary g-C3N4/Ti3AlC2 MAX and TiO2 NPs/Ti3AlC2 samples,respectively.A step-scheme(S-scheme)photocatalytic mechanism operates in this composite,suppressed the recombination of useful electron and holes and provides higher reduction potential for efficient CO2 conversion to CO and CH4.More im-portantly,when light intensity was increased by 5 folds,CH4 production rate was increased by 3.59 folds under visible light.The performance of composite catalyst was further investigated in a fixed-bed and monolith photoreactor and found monolithic support increased CO production by 2.64 folds,whereas,53.99 times lower CH4 production was noticed.The lower photocatalytic activity in a monolith photore-actor was due to lower visible light penetration into the microchannels.Thus,2D MAX Ti3AlC2 composite catalyst can be constructed for selective photocatalytic CO2 methanation under visible light in a fixed-bed photoreactor.

Department of Chemical Engineering,School of Chemical and Energy Engineering,Universiti Teknologi Malaysia,81310,UTM Johor Bahru,Malaysia;Chemical and Petroleum Engineering Department,UAE University,P.O.Box 15551,Al Ain,United Arab Emirates

[1]Muhammad Tahir;Beenish Tahir-.Constructing S-scheme 2D/OD g-C3N4/TiO2 NPs/MPs heterojunction with 2D-Ti3AlC2 MAX cocatalyst for photocatalytic CO2 reduction to CO/CH4 in fixed-bed and monolith photoreactors)[J].材料科学技术（英文版）,2022(11):195-210

photoreactors,Exfoliated,photoreac,photoreactor

Constructing,scheme,2D,OD,C3N4,TiO2,NPs,MPs,heterojunction,Ti3AlC2,MAX,cocatalyst,photocatalytic,CH4,fixed,bed,conductive,anchored,0D,has,been,explored,enhanced,photoreduction,particle,sizes,were,systematically,investigated,determine,effective,metal,support,interaction,faster,charge,carrier,separation,among,composite,materials,When,structure,folds,higher,production,was,observed,pared,anchoring,Maximum,yield,achieved,selectivity,using,ternary,which,binary,samples,respectively,step,mechanism,operates,this,suppressed,recombination,useful,electron,holes,provides,potential,efficient,conversion,More,portantly,when,light,intensity,increased,by,under,visible,performance,further,found,monolithic,whereas,times,lower,noticed,activity,due,penetration,into,microchannels,Thus,can,constructed,selective,methanation

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