Graphite imagawidwa m'magulu awiri: graphite yopangidwa ndi graphite ndi graphite yachilengedwe, yomwe ndi nkhokwe yotsimikizika padziko lonse ya graphite yachilengedwe yokwana matani pafupifupi 2 biliyoni.
Grafiti yopangidwa imapezeka mwa kuwola ndi kutentha zinthu zomwe zili ndi kaboni pansi pa mphamvu yachibadwa. Kusinthaku kumafuna kutentha ndi mphamvu zokwanira ngati mphamvu yoyendetsera, ndipo kapangidwe kosokonezeka kadzasinthidwa kukhala kapangidwe ka kristalo ka graphite kokonzedwa bwino.
Graphitization ndi njira yodziwika bwino ya zinthu za carbonaceous kudzera pa kutentha kwapamwamba kuposa 2000 ℃, koma zinthu zina za carbon zomwe zimagwiritsidwa ntchito pa kutentha kwapamwamba kuposa 3000 ℃, carbon imadziwika kuti "makala olimba", chifukwa cha zinthu zosavuta za carbon, njira yachikhalidwe ya graphitization imaphatikizapo kutentha kwakukulu ndi njira yopanikizika, graphitization yothandizira, njira yosungira nthunzi ya mankhwala, ndi zina zotero.
Kujambula zithunzi pogwiritsa ntchito graphitization ndi njira yothandiza kwambiri yogwiritsira ntchito zinthu zopatsa mphamvu kwambiri. Pambuyo pa kafukufuku wozama komanso wozama wa akatswiri, tsopano yakula. Komabe, zinthu zina zoyipa zimalepheretsa kugwiritsa ntchito graphitization yachikhalidwe m'mafakitale, kotero ndi njira yosapeŵeka kufufuza njira zatsopano zojambulira zithunzi pogwiritsa ntchito graphitization.
Njira yopangira electrolysis ya mchere wosungunuka kuyambira m'zaka za m'ma 1800 inali yopitilira zaka zana, chiphunzitso chake chachikulu ndi njira zatsopano nthawi zonse zimakhala zatsopano komanso chitukuko, tsopano sizimangokhala pamakampani achikhalidwe azitsulo, kumayambiriro kwa zaka za m'ma 2000, chitsulo mu dongosolo losungunuka la mchere wosungunuka, kukonzekera kuchepetsa kwa electrolytic oxide electrolytic kwa zitsulo zoyambira kwakhala cholinga chachikulu mu ntchito yogwira ntchito kwambiri,
Posachedwapa, njira yatsopano yokonzekera zinthu za graphite pogwiritsa ntchito electrolysis ya mchere wosungunuka yakopa chidwi cha anthu ambiri.
Pogwiritsa ntchito cathodic polarization ndi electrodeposition, mitundu iwiri yosiyana ya zinthu zopangira kaboni imasinthidwa kukhala zinthu za nano-graphite zokhala ndi phindu lalikulu. Poyerekeza ndi ukadaulo wachikhalidwe wa graphitization, njira yatsopano ya graphitization ili ndi ubwino wa kutentha kochepa kwa graphitization ndi mawonekedwe owongolera.
Pepalali likuwunikanso kupita patsogolo kwa graphitization pogwiritsa ntchito njira ya electrochemical, likuwonetsa ukadaulo watsopanowu, likuwunika zabwino ndi zoyipa zake, komanso likuwonetsa momwe zinthu zidzakhalire mtsogolo.
Choyamba, njira yosungunula mchere wa electrolytic cathode polarization
1.1 zinthu zopangira
Pakadali pano, graphite yopangira zinthu zazikulu ndi singano coke ndi phula coke yapamwamba kwambiri, yomwe ndi mafuta otsalira ndi malasha phula ngati zopangira zopangira zopangira mpweya wabwino kwambiri, wokhala ndi porosity yochepa, sulfure yochepa, phulusa lochepa komanso ubwino wa graphitization, pambuyo poikonza mu graphite imakhala ndi kukana kwabwino kwa kugunda, mphamvu yayikulu yamakina, kukana kotsika,
Komabe, kuchepa kwa mafuta osungidwa komanso kusinthasintha kwa mitengo ya mafuta kwachepetsa chitukuko chake, kotero kufunafuna zipangizo zatsopano kwakhala vuto lofunika kuthetsedwa mwachangu.
Njira zachikhalidwe zogwiritsira ntchito graphitization zili ndi zoletsa, ndipo njira zosiyanasiyana zogwiritsira ntchito graphitization zimagwiritsa ntchito zipangizo zosiyanasiyana zopangira. Pa carbon yosagwiritsidwa ntchito graphitized, njira zachikhalidwe sizingathe kuigwiritsa ntchito graphitized, pomwe njira yamagetsi ya electrochemical ya electrolysis ya mchere wosungunuka imaphwanya malire a zopangira, ndipo ndi yoyenera pafupifupi zipangizo zonse zachikhalidwe zogwiritsira ntchito carbon.
Zinthu zachikhalidwe za kaboni zimaphatikizapo kaboni wakuda, kaboni wokonzedwa, malasha, ndi zina zotero, zomwe malasha ndi omwe ali ndi chiyembekezo chachikulu. Inki yopangidwa ndi malasha imatenga malasha ngati chinthu choyambirira ndipo imakonzedwa kukhala zinthu za graphite kutentha kwambiri itatha kukonzedwa.
Posachedwapa, pepalali likupereka njira zatsopano zamagetsi, monga Peng, pogwiritsa ntchito electrolysis ya mchere wosungunuka, sizingatheke kuti graphitized carbon black ikhale crystallinity yapamwamba ya graphite, electrolysis ya zitsanzo za graphite zomwe zili ndi mawonekedwe a petal graphite nanometer chips, ili ndi malo apamwamba kwambiri, ikagwiritsidwa ntchito pa cathode ya batri ya lithiamu, ikuwonetsa bwino kwambiri electrochemical kuposa graphite yachilengedwe.
Zhu ndi anzake anaika malasha otsika mtengo omwe anakonzedwa mu dongosolo la mchere wosungunuka wa CaCl2 kuti agwiritsidwe ntchito ndi magetsi pa kutentha kwa 950 ℃, ndipo anasintha bwino malasha otsika mtengo kukhala graphite yokhala ndi kristalo wambiri, zomwe zinawonetsa magwiridwe antchito abwino komanso moyo wautali akagwiritsidwa ntchito ngati anode ya batri ya lithiamu ion.
Kuyeseraku kukuwonetsa kuti n'zotheka kusintha mitundu yosiyanasiyana ya zinthu zachikhalidwe za kaboni kukhala graphite pogwiritsa ntchito electrolysis ya mchere wosungunuka, zomwe zimatsegula njira yatsopano ya graphite yopangidwa mtsogolo.
1.2 njira yogwiritsira ntchito
Njira yoyeretsera mchere wosungunuka imagwiritsa ntchito zinthu za kaboni ngati cathode ndikuzisintha kukhala graphite yokhala ndi kristalo wambiri pogwiritsa ntchito cathodic polarization. Pakadali pano, mabuku omwe alipo akutchula kuchotsa mpweya ndi kukonzanso maatomu a kaboni mtunda wautali mu njira yosinthira cathodic polarization.
Kupezeka kwa mpweya mu zinthu za kaboni kudzalepheretsa graphitization pamlingo winawake. Mu njira yachikhalidwe yopangira graphitization, mpweya udzachotsedwa pang'onopang'ono kutentha kukapitirira 1600K. Komabe, ndikosavuta kwambiri kuchotsa oxidize kudzera mu cathodic polarization.
Peng, etc mu zoyeserera koyamba adayika patsogolo njira yosungunuka ya electrolysis ya cathodic polarization, yomwe ndi graphitization yomwe ingayambire ndikupezeka mu solid carbon microspheres/electrolyte interface, choyamba carbon microsphere imapangidwa mozungulira chipolopolo cha graphite cha m'mimba mwake chofanana, kenako maatomu a carbon carbon osakhazikika osafalikira ku graphite yakunja yokhazikika, mpaka graphit itakhala yokhazikika kwathunthu,
Njira yogwiritsira ntchito graphitization imaphatikizidwa ndi kuchotsa mpweya, zomwe zatsimikiziridwanso ndi zoyeserera.
Jin ndi anzake adatsimikiziranso mfundo imeneyi kudzera mu zoyeserera. Pambuyo pa carbonization ya shuga, graphitization (17% ya okosijeni) inachitika. Pambuyo pa graphitization, ma solid carbon sphere oyambirira (Chithunzi 1a ndi 1c) adapanga chipolopolo chokhala ndi ma nanosheets a graphite (Chithunzi 1b ndi 1d).
Pogwiritsa ntchito electrolysis ya ulusi wa kaboni (16% ya mpweya), ulusi wa kaboni ukhoza kusinthidwa kukhala machubu a graphite pambuyo pa graphitization malinga ndi njira yosinthira yomwe yafotokozedwa m'mabuku.
Ankakhulupirira kuti, kuyenda kwa mtunda wautali kuli pansi pa kugawanika kwa maatomu a kaboni ndi graphite yapamwamba kwambiri mpaka kaboni wosasinthika, kapangidwe kake ka graphite kamene kamapangidwa ndi ma petals apadera, koma kapangidwe kake ka graphite nanometer sikamveka bwino, monga momwe mpweya wochokera ku mafupa a kaboni umagwirira ntchito pambuyo pa momwe cathode imachitira, ndi zina zotero.
Pakadali pano, kafukufuku wokhudza makinawa akadali pagawo loyambirira, ndipo kafukufuku wowonjezera akufunika.
1.3 Kufotokozera kwa graphite yopangidwa
SEM imagwiritsidwa ntchito poona mawonekedwe a pamwamba pa graphite, TEM imagwiritsidwa ntchito poona mawonekedwe a kapangidwe kake osakwana 0.2 μm, XRD ndi Raman spectroscopy ndi njira zomwe zimagwiritsidwa ntchito kwambiri pofotokoza kapangidwe kake ka graphite, XRD imagwiritsidwa ntchito pofotokoza zambiri za kristalo ya graphite, ndipo Raman spectroscopy imagwiritsidwa ntchito pofotokoza zolakwika ndi kuchuluka kwa graphite.
Pali ma pores ambiri mu graphite omwe amakonzedwa ndi cathode polarization ya electrolysis ya mchere wosungunuka. Pazinthu zosiyanasiyana zopangira, monga electrolysis yakuda kwa kaboni, ma nanostructures okhala ndi ma petal-like porous amapezeka. Kusanthula kwa XRD ndi Raman spectrum kumachitika pa carbon black pambuyo pa electrolysis.
Pa kutentha kwa 827 ℃, mutalandira chithandizo cha 2.6V voltage kwa ola limodzi, chithunzi cha Raman spectral cha carbon black chimakhala chofanana ndi cha graphite yamalonda. Pambuyo poti carbon black yakonzedwa ndi kutentha kosiyanasiyana, graphite characteristic peak (002) imayesedwa. Nsonga ya diffraction (002) imayimira mulingo wa malo ozungulira a carbon layer mu graphite.
Kaboni ikakula kwambiri, imakhala yolunjika kwambiri.
Zhu anagwiritsa ntchito malasha otsika oyeretsedwa ngati cathode mu kuyeseraku, ndipo kapangidwe kake ka graphitized product kanasinthidwa kuchoka pa granular kukhala kapangidwe ka graphite yayikulu, ndipo graphite yolimba inawonedwanso pansi pa high rate transmission electron microscope.
Mu Raman spectra, ndi kusintha kwa zinthu zoyesera, mtengo wa ID/Ig unasinthanso. Pamene kutentha kwa electrolytic kunali 950 ℃, nthawi ya electrolytic inali 6h, ndipo voltage ya electrolytic inali 2.6V, mtengo wotsika kwambiri wa ID/Ig unali 0.3, ndipo D peak inali yotsika kwambiri kuposa G peak. Nthawi yomweyo, mawonekedwe a 2D peak adayimiranso kupangidwa kwa kapangidwe ka graphite kokonzedwa bwino.
Chiwongolero chakuthwa (002) cha diffraction pachithunzi cha XRD chimatsimikiziranso kusintha bwino kwa malasha otsika kukhala graphite yokhala ndi kristalo wambiri.
Mu ndondomeko ya graphitization, kuwonjezeka kwa kutentha ndi magetsi kudzagwira ntchito yokweza, koma magetsi okwera kwambiri amachepetsa kukolola kwa graphite, ndipo kutentha kwambiri kapena nthawi yayitali kwambiri ya graphitization idzapangitsa kuti zinthu ziwonongeke, kotero pa zipangizo zosiyanasiyana za kaboni, ndikofunikira kwambiri kufufuza mikhalidwe yoyenera kwambiri ya electrolytic, komanso cholinga ndi zovuta.
Kapangidwe kake kameneka kofanana ndi petal kali ndi mphamvu zabwino kwambiri zamagetsi. Ma pores ambiri amalola ma ayoni kulowetsedwa/kuchotsedwa mwachangu, zomwe zimapangitsa kuti zinthu za cathode zapamwamba zikhale bwino kwambiri pamabatire, ndi zina zotero. Chifukwa chake, graphitization ya njira yamagetsi ndi njira yabwino kwambiri yogwiritsira ntchito graphitization.
Njira yokhazikitsira ma electrode a mchere wosungunuka
2.1 Kuyika kwa kaboni dayokisaidi m'maelekitirodi
Popeza mpweya wofunika kwambiri wowonjezera kutentha, CO2 ndi chinthu chopanda poizoni, chopanda vuto, chotsika mtengo komanso chopezeka mosavuta chobwezerezedwanso. Komabe, mpweya wa kaboni mu CO2 uli mu mkhalidwe wapamwamba kwambiri wa okosijeni, kotero CO2 ili ndi kukhazikika kwakukulu kwa thermodynamic, zomwe zimapangitsa kuti zikhale zovuta kugwiritsanso ntchito.
Kafukufuku woyamba kwambiri pa malo a electrode a CO2 anachitika m'zaka za m'ma 1960. Ingram ndi anzake adapanga bwino carbon pa electrode yagolide mu dongosolo la mchere wosungunuka wa Li2CO3-Na2CO3-K2CO3.
Van et al. adanenanso kuti ufa wa kaboni womwe umapezeka pamitundu yosiyanasiyana ya mphamvu zochepetsera unali ndi kapangidwe kosiyana, kuphatikizapo graphite, kaboni wosasinthika ndi ulusi wa kaboni.
Pogwiritsa ntchito mchere wosungunuka kuti agwire CO2 ndi njira yokonzekera zinthu za kaboni, akatswiri ofufuza atakhala nthawi yayitali akuyang'ana kwambiri pa njira yopangira mpweya woipa komanso momwe zinthu zamagetsi zimakhudzira zinthu zomaliza, zomwe zimaphatikizapo kutentha kwa electrolytic, magetsi a electrolytic ndi kapangidwe ka mchere wosungunuka ndi ma electrodes, ndi zina zotero, kukonzekera kwa zinthu za graphite zomwe zimagwiritsidwa ntchito kwambiri kuti CO2 ikhale ndi magetsi kwakhazikitsa maziko olimba.
Mwa kusintha electrolyte ndikugwiritsa ntchito njira ya mchere wosungunuka yochokera ku CaCl2 yokhala ndi mphamvu yogwira bwino ya CO2, Hu et al. adakonza bwino graphene yokhala ndi digiri yapamwamba ya graphitization ndi ma nanotubes a kaboni ndi kapangidwe kena ka nanographite pophunzira mikhalidwe ya electrolytic monga kutentha kwa electrolysis, kapangidwe ka electrode ndi kapangidwe ka mchere wosungunuka.
Poyerekeza ndi dongosolo la carbonate, CaCl2 ili ndi ubwino woti ndi yotsika mtengo komanso yosavuta kupeza, imakhala ndi mphamvu zambiri zoyendetsera mpweya, yosavuta kusungunuka m'madzi, komanso imasungunuka kwambiri m'madzi, zomwe zimapangitsa kuti CO2 isinthe kukhala zinthu za graphite zomwe zimakhala ndi phindu lalikulu.
2.2 Njira Yosinthira
Kukonzekera zinthu za kaboni wowonjezera mtengo kwambiri pogwiritsa ntchito ma electrode a CO2 kuchokera ku mchere wosungunuka kumaphatikizapo kugwidwa kwa CO2 ndi kuchepetsa mwachindunji. Kugwidwa kwa CO2 kumatsirizidwa ndi mchere wosungunuka waulere wa O2- mu, monga momwe zasonyezedwera mu Equation (1):
CO2+O2-→CO3 2- (1)
Pakadali pano, njira zitatu zochepetsera zinthu mosalunjika zaperekedwa: njira imodzi yochitira zinthu, njira ziwiri zochitira zinthu komanso njira yochepetsera zinthu pogwiritsa ntchito zitsulo.
Njira yochitira zinthu imodzi inayamba kuperekedwa ndi Ingram, monga momwe zasonyezedwera mu Equation (2):
CO3 2-+ 4E – →C+3O2- (2)
Njira yochitira zinthu ziwiri inaperekedwa ndi Borucka et al., monga momwe zasonyezedwera mu Equation (3-4):
CO3 2-+ 2E – →CO2 2-+O2- (3)
CO2 2-+ 2E – →C+2O2- (4)
Njira yochepetsera chitsulo inaperekedwa ndi Deanhardt et al. Iwo ankakhulupirira kuti ma ayoni achitsulo poyamba ankachepetsedwa kukhala chitsulo mu cathode, kenako chitsulocho chinachepetsedwa kukhala ma ayoni a carbonate, monga momwe zasonyezedwera mu Equation (5~6):
M- + E – →M (5)
4 m + M2CO3 – > C + 3 m2o (6)
Pakadali pano, njira yochitira zinthu imodzi yokha ikuvomerezedwa m'mabuku omwe alipo.
Yin ndi anzake adaphunzira za Li-Na-K carbonate system yokhala ndi nickel ngati cathode, tin dioxide ngati anode ndi siliva waya ngati reference electrode, ndipo adapeza cyclic voltammetry test figure mu Chithunzi 2 (scanning rate ya 100 mV/s) pa nickel cathode, ndipo adapeza kuti panali reduction peak imodzi yokha (pa -2.0V) mu negative scanning.
Chifukwa chake, tinganene kuti chinthu chimodzi chokha chinachitika panthawi yochepetsa carbonate.
Gao ndi anzake adapeza cyclic voltammetry yofanana mu carbonate system yomweyi.
Ge ndi ena adagwiritsa ntchito anode yosagwira ntchito ndi tungsten cathode kuti agwire CO2 mu dongosolo la LiCl-Li2CO3 ndipo adapeza zithunzi zofanana, ndipo kuchepa kwa mpweya woipa kunangowonekera mu negative scanning.
Mu dongosolo la mchere wosungunuka wachitsulo cha alkaline, zitsulo za alkali ndi CO zidzapangidwa pamene kaboni ikuyikidwa ndi cathode. Komabe, chifukwa chakuti zinthu zomwe zimachitika chifukwa cha kutentha kwa kaboni zimakhala zochepa pa kutentha kochepa, kuchepa kwa carbonate kukhala kaboni kokha ndiko kungadziwike mu kuyesaku.
2.3 Kugwira CO2 ndi mchere wosungunuka kuti akonze zinthu za graphite
Zinthu zopangidwa ndi graphite zapamwamba kwambiri monga graphene ndi carbon nanotubes zimatha kukonzedwa pogwiritsa ntchito electrodeposition ya CO2 kuchokera ku mchere wosungunuka poyang'anira momwe zinthu zilili. Hu et al. adagwiritsa ntchito chitsulo chosapanga dzimbiri ngati cathode mu CaCl2-NaCl-CaO melted salt system ndipo adayikidwa electrolys kwa maola 4 pansi pa 2.6V constant voltage pa kutentha kosiyanasiyana.
Chifukwa cha kupangika kwa chitsulo ndi mphamvu ya CO pakati pa zigawo za graphite, graphene inapezeka pamwamba pa cathode. Njira yokonzekera graphene ikuwonetsedwa mu Chithunzi 3.
Chithunzicho
Pambuyo pake maphunziro anawonjezera Li2SO4 pamaziko a CaCl2-NaClCaO dongosolo la mchere wosungunuka, kutentha kwa electrolysis kunali 625 ℃, pambuyo pa maola 4 a electrolysis, nthawi yomweyo mu cathodic deposition ya carbon anapeza graphene ndi carbon nanotubes, kafukufukuyu anapeza kuti Li+ ndi SO4 2- kubweretsa zotsatira zabwino pa graphitization.
Sulfure imaphatikizidwanso bwino mu thupi la kaboni, ndipo mapepala a graphite owonda kwambiri ndi kaboni wopyapyala amatha kupezeka powongolera momwe zinthu zilili mu electrolytic.
Zinthu monga kutentha kwa electrolytic kwapamwamba ndi kotsika kwa graphene ndikofunikira kwambiri, pamene kutentha kopitilira 800 ℃ ndikosavuta kupanga CO m'malo mwa kaboni, pafupifupi palibe mpweya woipa kuposa 950 ℃, kotero kulamulira kutentha ndikofunikira kwambiri popanga graphene ndi machubu a kaboni, ndikubwezeretsa kufunika kwa mpweya woipa womwe umapangidwa ndi CO2 kuti cathode ipange graphene yokhazikika.
Ntchito zimenezi zimapereka njira yatsopano yokonzekera zinthu zopangidwa ndi nano-graphite ndi CO2, zomwe ndizofunikira kwambiri pa yankho la mpweya woipa komanso kukonzekera graphene.
3. Chidule ndi Kawonedwe
Ndi chitukuko chachangu cha mafakitale atsopano amagetsi, graphite yachilengedwe yalephera kukwaniritsa zomwe zikufunidwa pano, ndipo graphite yopangidwa ndi zinthu zachilengedwe ili ndi mphamvu zabwino komanso zamakemikolo kuposa graphite yachilengedwe, kotero graphitization yotsika mtengo, yogwira ntchito bwino komanso yosawononga chilengedwe ndi cholinga cha nthawi yayitali.
Njira zamagetsi zoyezera graphitization mu zinthu zolimba ndi za gasi pogwiritsa ntchito njira ya cathodic polarization ndi electrochemical deposition zidatuluka bwino kuchokera ku zinthu za graphite zomwe zili ndi phindu lalikulu, poyerekeza ndi njira yachikhalidwe yoyezera graphitization, njira zamagetsi ndi yothandiza kwambiri, kugwiritsa ntchito mphamvu zochepa, kuteteza chilengedwe chobiriwira, chifukwa cha zinthu zazing'ono zomwe zimasankhidwa nthawi imodzi, malinga ndi momwe zinthu zosiyanasiyana zimachitikira, zimatha kukonzedwa pamitundu yosiyanasiyana ya kapangidwe ka graphite.
Imapereka njira yothandiza kuti mitundu yonse ya mpweya wopanda mpweya ndi mpweya wowonjezera kutentha isinthidwe kukhala zinthu zamtengo wapatali zopangidwa ndi graphite ndipo ili ndi mwayi wabwino wogwiritsidwa ntchito.
Pakadali pano, ukadaulo uwu uli pa chiyambi chake. Pali maphunziro ochepa okhudza graphitization pogwiritsa ntchito njira ya electrochemical, ndipo pali njira zambiri zosadziwika. Chifukwa chake, ndikofunikira kuyambira pazinthu zopangira ndikuchita kafukufuku wathunthu komanso wolongosoka pa ma carbon osiyanasiyana a amorphous, ndikuwunikanso thermodynamics ndi mphamvu za kusintha kwa graphite mozama.
Izi zili ndi tanthauzo lalikulu pakukula kwa mtsogolo kwa mafakitale a graphite.
Nthawi yotumizira: Meyi-10-2021