Graphite muab faib ua graphite dag thiab graphite ntuj, thiab lub ntiaj teb cov pov thawj pov thawj ntawm graphite ntuj yog kwv yees li 2 billion tons.
Cov graphite cuav yog tau los ntawm kev rhuav tshem thiab kho cua sov ntawm cov khoom uas muaj cov pa roj carbon nyob rau hauv qhov siab ib txwm muaj. Qhov kev hloov pauv no xav tau qhov kub thiab lub zog txaus ua lub zog tsav tsheb, thiab cov qauv tsis sib xws yuav raug hloov mus rau hauv cov qauv siv lead ua graphite.
Graphitization yog nyob rau hauv lub ntsiab lus dav dav ntawm cov khoom siv carbonaceous los ntawm saum 2000 ℃ kub kub kho cua sov carbon atoms rearranged, txawm li cas los xij qee cov khoom siv carbon nyob rau hauv qhov kub siab tshaj 3000 ℃ graphitization, cov khoom siv carbon no hu ua "nyuj charcoal", rau cov khoom siv carbon graphitized yooj yim, cov txheej txheem graphitization ib txwm muaj xws li kub thiab siab siab txoj kev, catalytic graphitization, tshuaj lom neeg vapor deposition txoj kev, thiab lwm yam.
Kev siv graphitization yog ib txoj hauv kev zoo rau kev siv cov khoom siv carbonaceous uas muaj nqis ntxiv. Tom qab kev tshawb fawb ntau thiab tob los ntawm cov kws tshawb fawb, nws yeej loj hlob tam sim no. Txawm li cas los xij, qee yam tsis zoo ua rau kev siv graphitization ib txwm muaj kev txwv hauv kev lag luam, yog li nws yog ib qho kev hloov pauv tsis tau los tshawb nrhiav cov txheej txheem graphitization tshiab.
Txij li thaum xyoo pua 19th, txoj kev siv hluav taws xob los ntawm cov ntsev yaj tau tsim ntau tshaj ib puas xyoo, nws txoj kev xav yooj yim thiab cov txheej txheem tshiab yog kev tsim kho tshiab tas li, tam sim no tsis txwv rau kev lag luam hlau ib txwm muaj, thaum pib ntawm xyoo pua 21st, cov hlau hauv cov ntsev yaj tau tsim cov khoom siv oxide electrolytic txo cov hlau hauv cov txheej txheem tau dhau los ua qhov tseem ceeb hauv kev ua haujlwm ntau dua,
Tsis ntev los no, ib txoj kev tshiab rau kev npaj cov ntaub ntawv graphite los ntawm cov ntsev electrolysis tau nyiam ntau qhov kev saib xyuas.
Los ntawm kev siv cathodic polarization thiab electrodeposition, ob hom carbon raw khoom sib txawv raug hloov mus ua cov khoom siv nano-graphite nrog tus nqi ntxiv siab. Piv nrog rau cov thev naus laus zis graphitization ib txwm muaj, txoj kev graphitization tshiab muaj qhov zoo ntawm qhov kub qis dua graphitization thiab morphology tswj tau.
Tsab ntawv no tshuaj xyuas qhov kev nce qib ntawm graphitization los ntawm txoj kev electrochemical, qhia txog cov thev naus laus zis tshiab no, tshuaj xyuas nws cov txiaj ntsig thiab qhov tsis zoo, thiab kwv yees nws txoj kev loj hlob yav tom ntej.
Ua ntej, txoj kev polarization ntawm cov ntsev molten electrolytic cathode
1.1 cov khoom siv raw
Tam sim no, cov khoom siv tseem ceeb ntawm cov graphite dag yog koob coke thiab suab coke ntawm qib siab graphitization, uas yog los ntawm cov roj seem thiab thee tar ua cov khoom siv raw los tsim cov khoom siv carbon zoo, nrog cov porosity tsawg, tsawg sulfur, tsawg tshauv thiab qhov zoo ntawm graphitization, tom qab nws npaj rau hauv graphite muaj kev tiv thaiv zoo rau kev cuam tshuam, siab mechanical zog, qis resistivity,
Txawm li cas los xij, cov roj khaws cia tsawg thiab cov nqi roj hloov pauv tau txwv nws txoj kev loj hlob, yog li nrhiav cov khoom siv raw tshiab tau dhau los ua teeb meem ceev uas yuav tsum tau daws.
Cov txheej txheem graphitization ib txwm muaj cov kev txwv, thiab cov txheej txheem graphitization sib txawv siv cov khoom siv raw sib txawv. Rau cov pa roj carbon uas tsis yog graphitized, cov txheej txheem ib txwm tsis tuaj yeem graphitize nws, thaum cov mis electrochemical ntawm cov ntsev molten electrolysis tawg los ntawm qhov txwv ntawm cov khoom siv raw, thiab nws haum rau yuav luag txhua cov ntaub ntawv carbon ib txwm muaj.
Cov ntaub ntawv carbon ib txwm muaj xws li carbon dub, activated carbon, thee, thiab lwm yam, uas thee yog qhov zoo tshaj plaws. Cov kua mem uas ua los ntawm thee siv thee ua cov khoom ua ntej thiab tom qab kho ua ntej, nws tau npaj ua cov khoom graphite ntawm qhov kub siab.
Tsis ntev los no, tsab ntawv no tau hais txog cov txheej txheem electrochemical tshiab, xws li Peng, los ntawm cov ntsev molten electrolysis tsis zoo li yuav ua rau cov pa roj carbon dub graphite rau hauv cov crystallinity siab ntawm graphite. Cov qauv graphite uas muaj cov duab paj ntawm graphite nanometer chips hauv electrolysis muaj thaj chaw tshwj xeeb siab, thaum siv rau cov roj teeb lithium cathode qhia tau tias muaj kev ua tau zoo electrochemical ntau dua li cov graphite ntuj.
Zhu et al. muab cov thee tsis zoo uas tau kho kom huv si rau hauv CaCl2 molten ntsev system rau electrolysis ntawm 950 ℃, thiab ua tiav hloov cov thee tsis zoo mus rau hauv graphite nrog crystallinity siab, uas qhia tau tias muaj kev ua tau zoo thiab lub neej ntev thaum siv ua anode ntawm lithium ion roj teeb.
Qhov kev sim qhia tau hais tias nws muaj peev xwm hloov ntau hom khoom siv carbon ib txwm mus rau hauv graphite los ntawm kev siv cov ntsev electrolysis, uas qhib txoj hauv kev tshiab rau cov graphite hluavtaws yav tom ntej.
1.2 lub tshuab ntawm
Txoj kev electrolysis ntsev uas yaj siv cov khoom siv carbon ua cathode thiab hloov nws mus rau hauv graphite nrog crystallinity siab los ntawm kev siv cathodic polarization. Tam sim no, cov ntaub ntawv uas twb muaj lawm hais txog kev tshem tawm cov pa oxygen thiab kev hloov pauv ntev ntawm cov pa roj carbon hauv cov txheej txheem hloov pauv ntawm cathodic polarization.
Qhov muaj cov pa oxygen nyob rau hauv cov khoom siv carbon yuav cuam tshuam rau qee qhov graphitization. Hauv cov txheej txheem graphitization ib txwm muaj, cov pa oxygen yuav maj mam tshem tawm thaum qhov kub siab dua 1600K. Txawm li cas los xij, nws yooj yim heev rau deoxidize los ntawm cathodic polarization.
Peng, thiab lwm yam hauv kev sim thawj zaug tau muab tso rau pem hauv ntej cov ntsev molten electrolysis cathodic polarization potential mechanism, uas yog qhov graphitization feem ntau qhov chaw pib yog nyob rau hauv cov khoom carbon microspheres / electrolyte interface, thawj carbon microsphere tsim nyob ib puag ncig lub plhaub graphite tib lub cheeb tsam, thiab tom qab ntawd yeej tsis ruaj khov carbon anhydrous carbon atoms kis mus rau sab nraud ruaj khov dua graphite flake, kom txog thaum tiav graphitized,
Cov txheej txheem graphitization yog nrog los ntawm kev tshem tawm cov pa oxygen, uas kuj tau lees paub los ntawm kev sim.
Jin et al. kuj tau ua pov thawj qhov kev xav no los ntawm kev sim. Tom qab carbonization ntawm glucose, graphitization (17% cov pa oxygen) tau ua tiav. Tom qab graphitization, cov khoom qub carbon spheres (Daim Duab 1a thiab 1c) tsim ib lub plhaub porous uas muaj cov graphite nanosheets (Daim Duab 1b thiab 1d).
Los ntawm electrolysis ntawm cov carbon fibers (16% oxygen), cov carbon fibers yuav raug hloov mus rau hauv cov raj graphite tom qab graphitization raws li cov txheej txheem hloov pauv uas tau xav hauv cov ntaub ntawv.
Ntseeg tau tias, qhov kev txav mus los deb yog nyob rau hauv cathodic polarization ntawm cov pa roj carbon atoms lub siab crystal graphite rau amorphous carbon rearrange yuav tsum tau ua, synthetic graphite tshwj xeeb petals duab nanostructures tau txais txiaj ntsig los ntawm cov pa oxygen los ntawm, tab sis qhov tshwj xeeb yuav ua li cas cuam tshuam rau graphite nanometer qauv tsis meej, xws li oxygen los ntawm cov pa roj carbon skeleton tom qab li cas ntawm cathode reaction, thiab lwm yam.
Tam sim no, kev tshawb fawb txog lub tshuab tseem nyob rau theem pib, thiab xav tau kev tshawb fawb ntxiv.
1.3 Kev piav qhia txog morphological ntawm cov graphite hluavtaws
SEM siv los soj ntsuam qhov microscopic surface morphology ntawm graphite, TEM siv los soj ntsuam qhov structural morphology ntawm tsawg dua 0.2 μm, XRD thiab Raman spectroscopy yog cov cuab yeej siv feem ntau los piav qhia txog microstructure ntawm graphite, XRD siv los piav qhia txog cov ntaub ntawv siv lead ua ntawm graphite, thiab Raman spectroscopy siv los piav qhia txog qhov tsis zoo thiab qib kev txiav txim ntawm graphite.
Muaj ntau lub qhov hws hauv graphite uas tau npaj los ntawm cathode polarization ntawm molten salt electrolysis. Rau cov khoom siv raw sib txawv, xws li carbon black electrolysis, cov qauv porous zoo li paj tau txais. XRD thiab Raman spectrum analysis tau ua rau carbon black tom qab electrolysis.
Ntawm 827 ℃, tom qab kho nrog 2.6V voltage rau 1 teev, daim duab Raman spectral ntawm cov pa roj carbon dub yuav luag zoo ib yam li cov graphite lag luam. Tom qab kho cov pa roj carbon dub nrog ntau qhov kub sib txawv, qhov siab tshaj plaws ntawm cov yam ntxwv graphite ntse (002) raug ntsuas. Qhov siab tshaj plaws diffraction (002) sawv cev rau qib kev taw qhia ntawm cov txheej carbon aromatic hauv graphite.
Cov txheej carbon ntse dua, nws qhov kev taw qhia ntau dua.
Zhu siv cov thee uas tsis muaj zog ua cov cathode hauv kev sim, thiab cov qauv me me ntawm cov khoom graphitized tau hloov pauv los ntawm cov qauv granular mus rau cov qauv graphite loj, thiab cov txheej graphite nruj kuj tau pom nyob rau hauv lub tshuab hluav taws xob kis tau tus nqi siab.
Hauv Raman spectra, nrog rau kev hloov pauv ntawm cov xwm txheej sim, tus nqi ID / Ig kuj hloov pauv. Thaum qhov kub electrolytic yog 950 ℃, lub sijhawm electrolytic yog 6 teev, thiab qhov hluav taws xob electrolytic yog 2.6V, tus nqi ID / Ig qis tshaj plaws yog 0.3, thiab D peak qis dua G peak. Tib lub sijhawm, qhov tshwm sim ntawm 2D peak kuj sawv cev rau kev tsim cov qauv graphite siab heev.
Lub ncov diffraction ntse (002) hauv daim duab XRD kuj lees paub qhov kev hloov pauv zoo ntawm cov thee qis dua mus rau hauv graphite nrog crystallinity siab.
Hauv cov txheej txheem graphitization, qhov nce ntawm qhov kub thiab voltage yuav ua lub luag haujlwm txhawb nqa, tab sis qhov voltage siab dhau yuav txo qhov tsim tawm ntawm graphite, thiab qhov kub siab dhau lossis lub sijhawm graphitization ntev dhau yuav ua rau muaj kev pov tseg ntawm cov peev txheej, yog li rau cov ntaub ntawv carbon sib txawv, nws yog qhov tseem ceeb tshwj xeeb los tshawb nrhiav cov xwm txheej electrolytic tsim nyog tshaj plaws, kuj yog qhov tseem ceeb thiab qhov nyuaj.
Cov qauv nanostructure zoo li paj no muaj cov khoom siv hluav taws xob zoo heev. Muaj ntau lub qhov hws tso cai rau cov ions kom sai sai ntxig / deembedded, muab cov khoom siv cathode zoo rau cov roj teeb, thiab lwm yam. Yog li ntawd, txoj kev electrochemical graphitization yog ib txoj kev graphitization muaj peev xwm heev.
Txoj kev electrodeposition ntsev molten
2.1 Kev siv cov pa roj carbon dioxide los ua cov electrode
Raws li cov pa roj av tseem ceeb tshaj plaws, CO2 kuj yog cov khoom siv uas tsis muaj tshuaj lom, tsis muaj teeb meem, pheej yig thiab yooj yim nrhiav tau dua tshiab. Txawm li cas los xij, cov pa roj carbon hauv CO2 nyob rau hauv lub xeev oxidation siab tshaj plaws, yog li CO2 muaj kev ruaj khov thermodynamic siab, uas ua rau nws nyuaj rau rov siv dua.
Cov kev tshawb fawb thaum ntxov tshaj plaws ntawm CO2 electrodeposition tuaj yeem taug qab rov qab mus rau xyoo 1960. Ingram et al. tau ua tiav npaj cov pa roj carbon ntawm cov electrode kub hauv lub cev ntsev molten ntawm Li2CO3-Na2CO3-K2CO3.
Van et al. tau taw qhia tias cov hmoov carbon uas tau txais ntawm ntau qhov kev txo qis muaj cov qauv sib txawv, suav nrog graphite, amorphous carbon thiab carbon nanofibers.
Los ntawm kev siv cov ntsev molten los ntes CO2 thiab kev npaj cov khoom siv carbon kom ua tiav, tom qab lub sijhawm ntev ntawm kev tshawb fawb cov kws tshawb fawb tau tsom mus rau cov txheej txheem tsim cov pa roj carbon thiab cov nyhuv ntawm cov xwm txheej electrolysis rau cov khoom kawg, uas suav nrog qhov kub electrolytic, electrolytic voltage thiab cov khoom sib xyaw ntawm cov ntsev molten thiab electrodes, thiab lwm yam., kev npaj cov khoom siv graphite ua tau zoo rau kev electrodeposition ntawm CO2 tau tso lub hauv paus ruaj khov.
Los ntawm kev hloov cov electrolyte thiab siv CaCl2-based molten salt system nrog kev ua haujlwm siab dua ntawm CO2, Hu et al. tau ua tiav npaj graphene nrog qib graphitization siab dua thiab carbon nanotubes thiab lwm yam nanographite qauv los ntawm kev kawm txog cov xwm txheej electrolytic xws li qhov kub electrolysis, electrode composition thiab molten salt composition.
Piv nrog rau lub kaw lus carbonate, CaCl2 muaj qhov zoo ntawm pheej yig thiab yooj yim tau txais, muaj kev coj ua siab, yooj yim yaj hauv dej, thiab muaj peev xwm yaj tau ntau dua ntawm cov pa oxygen, uas muab cov xwm txheej theoretical rau kev hloov pauv ntawm CO2 mus rau hauv cov khoom graphite nrog tus nqi ntxiv siab.
2.2 Lub Tswv Yim Hloov Pauv
Kev npaj cov khoom siv carbon uas muaj nqis ntxiv los ntawm electrodeposition ntawm CO2 los ntawm cov ntsev molten feem ntau suav nrog CO2 kev ntes thiab kev txo qis tsis ncaj qha. Kev ntes CO2 yog ua tiav los ntawm O2- dawb hauv cov ntsev molten, raws li qhia hauv Equation (1):
CO2+O2-→CO3 2- (1)
Tam sim no, peb txoj kev txo qis tsis ncaj qha tau raug pom zoo: ib kauj ruam kev tshuaj tiv thaiv, ob kauj ruam kev tshuaj tiv thaiv thiab cov txheej txheem txo cov hlau.
Lub tshuab ua ib kauj ruam tau raug thawj zaug los ntawm Ingram, raws li tau pom hauv Equation (2):
CO3 2-+ 4E – →C+3O2- (2)
Lub tshuab ua ob kauj ruam tau raug tsim los ntawm Borucka et al., raws li tau pom hauv Equation (3-4):
CO3 2-+ 2E → CO2 2-+ O2- (3)
CO2 2-+ 2E – →C+2O2- (4)
Lub tshuab ntawm cov tshuaj tiv thaiv hlau tau raug tsim los ntawm Deanhardt et al. Lawv ntseeg tias cov hlau ions tau raug txo kom ua hlau hauv cathode, thiab tom qab ntawd cov hlau tau raug txo kom ua carbonate ions, raws li qhia hauv Equation (5 ~ 6):
M- + E – →M (5)
4 m + M2CO3 – > C + 3 m2o (6)
Tam sim no, cov txheej txheem ib kauj ruam feem ntau lees txais hauv cov ntaub ntawv uas twb muaj lawm.
Yin et al. tau kawm txog Li-Na-K carbonate system nrog nickel ua cathode, tin dioxide ua anode thiab silver wire ua reference electrode, thiab tau txais daim duab cyclic voltammetry test hauv Daim Duab 2 (scanning rate ntawm 100 mV/s) ntawm nickel cathode, thiab pom tias tsuas muaj ib qho reduction peak (ntawm -2.0V) hauv negative scanning.
Yog li ntawd, nws tuaj yeem xaus lus tias tsuas yog ib qho kev cuam tshuam tshwm sim thaum lub sijhawm txo qis ntawm carbonate.
Gao et al. tau txais tib lub cyclic voltammetry hauv tib lub carbonate system.
Ge et al. siv inert anode thiab tungsten cathode los ntes CO2 hauv LiCl-Li2CO3 system thiab tau txais cov duab zoo sib xws, thiab tsuas yog qhov txo qis ntawm cov pa roj carbon deposition tshwm sim hauv qhov kev luam theej tsis zoo.
Hauv cov alkaline hlau molten ntsev system, alkali hlau thiab CO yuav tsim tawm thaum cov pa roj carbon raug tso los ntawm cathode. Txawm li cas los xij, vim tias cov xwm txheej thermodynamic ntawm cov pa roj carbon deposition reaction qis dua ntawm qhov kub qis dua, tsuas yog qhov txo qis ntawm carbonate rau carbon tuaj yeem pom hauv kev sim.
2.3 Kev ntes CO2 los ntawm cov ntsev yaj los npaj cov khoom graphite
Cov khoom siv graphite nano uas muaj nqi ntxiv xws li graphene thiab carbon nanotubes tuaj yeem npaj tau los ntawm electrodeposition ntawm CO2 los ntawm cov ntsev molten los ntawm kev tswj cov xwm txheej sim. Hu et al. siv cov hlau tsis xeb ua cathode hauv CaCl2-NaCl-CaO molten ntsev system thiab electrolyzed rau 4 teev nyob rau hauv qhov xwm txheej ntawm 2.6V qhov hluav taws xob tas li ntawm qhov kub sib txawv.
Ua tsaug rau qhov catalysis ntawm hlau thiab qhov cuam tshuam tawg ntawm CO ntawm cov txheej graphite, graphene tau pom nyob rau ntawm qhov chaw ntawm cathode. Cov txheej txheem npaj ntawm graphene tau qhia nyob rau hauv daim duab 3.
Daim duab
Cov kev tshawb fawb tom qab ntawd tau ntxiv Li2SO4 raws li CaCl2-NaClCaO molten ntsev system, qhov kub ntawm electrolysis yog 625 ℃, tom qab 4 teev ntawm electrolysis, tib lub sijhawm hauv cathodic deposition ntawm cov pa roj carbon pom graphene thiab carbon nanotubes, kev tshawb fawb pom tias Li + thiab SO4 2- coj cov txiaj ntsig zoo rau graphitization.
Cov sulfur kuj tau koom ua ke zoo rau hauv lub cev carbon, thiab cov ntawv graphite ultra-thin thiab cov pa roj carbon filamentous tuaj yeem tau txais los ntawm kev tswj cov xwm txheej electrolytic.
Cov khoom siv xws li qhov kub thiab txias electrolytic ntawm siab thiab qis rau kev tsim graphene yog qhov tseem ceeb, thaum qhov kub siab tshaj 800 ℃ yooj yim dua los tsim CO es tsis txhob carbon, yuav luag tsis muaj carbon deposition thaum siab tshaj 950 ℃, yog li kev tswj qhov kub thiab txias yog qhov tseem ceeb heev los tsim graphene thiab carbon nanotubes, thiab rov qab kho qhov xav tau carbon deposition reaction CO reaction synergy kom ntseeg tau tias cathode los tsim graphene ruaj khov.
Cov haujlwm no muab ib txoj hauv kev tshiab rau kev npaj cov khoom nano-graphite los ntawm CO2, uas yog qhov tseem ceeb heev rau kev daws teeb meem ntawm cov pa roj av thiab kev npaj graphene.
3. Kev Txheeb Xyuas thiab Kev Xav Tau
Nrog rau kev txhim kho sai ntawm kev lag luam zog tshiab, graphite ntuj tsis tau ua kom tau raws li qhov xav tau tam sim no, thiab graphite dag muaj cov khoom siv lub cev thiab tshuaj zoo dua li graphite ntuj, yog li pheej yig, ua haujlwm tau zoo thiab zoo rau ib puag ncig yog lub hom phiaj ntev.
Cov txheej txheem electrochemical graphitization hauv cov khoom siv raw khoom thiab cov roj av nrog txoj kev cathodic polarization thiab electrochemical deposition tau ua tiav tawm ntawm cov ntaub ntawv graphite nrog tus nqi ntxiv siab, piv rau txoj kev ib txwm ntawm graphitization, txoj kev electrochemical yog qhov ua tau zoo dua, siv hluav taws xob tsawg dua, tiv thaiv ib puag ncig ntsuab, rau cov khoom me me txwv los ntawm cov ntaub ntawv xaiv tib lub sijhawm, raws li cov xwm txheej electrolysis sib txawv tuaj yeem npaj ntawm cov qauv graphite sib txawv,
Nws muab ib txoj hauv kev zoo rau txhua yam amorphous carbon thiab cov pa roj av kom hloov mus ua cov ntaub ntawv graphite nano-structured muaj nqis thiab muaj kev cia siab zoo rau kev siv.
Tam sim no, cov thev naus laus zis no tseem nyob rau hauv nws thaum yau. Muaj ob peb txoj kev tshawb fawb txog graphitization los ntawm txoj kev electrochemical, thiab tseem muaj ntau cov txheej txheem tsis paub. Yog li ntawd, nws yog qhov tsim nyog los pib los ntawm cov khoom siv raw thiab ua ib qho kev tshawb fawb dav dav thiab kev tshawb fawb txog ntau yam amorphous carbons, thiab tib lub sijhawm tshawb nrhiav thermodynamics thiab dynamics ntawm graphite hloov pauv hauv qib tob dua.
Cov no muaj lub ntsiab lus tseem ceeb rau kev txhim kho yav tom ntej ntawm kev lag luam graphite.
Lub sijhawm tshaj tawm: Tsib Hlis-10-2021