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I-electrocatalysts esebenzayo, engabizi kwaye ehlala ixesha elide yokunciphisa i-oksijeni (ORR) ibaluleke kakhulu kwiibhetri zesibini ze-Zn-air.Umsebenzi we-ORR we-oxide yensimbi enye kunye nexubeneyo kunye ne-carbon electrocatalysts yaphandwa ngokusebenzisa imilinganiselo ye-disk electrode (RDE), i-slopes ye-Tafel, kunye ne-Kutetsky-Levich plots.Kufunyenwe ukuba ukudibanisa kwe-MnOx kunye ne-XC-72R kubonisa umsebenzi ophezulu we-PBP kunye nokuzinza okulungileyo, ukuya kwi-100 mA cm-2.Ukusebenza kwee-electrode ze-ORR ezikhethiweyo kunye ne-electrode ephuculweyo ye-oxygen evolution (OER) emva koko yavavanywa kwibhetri ye-zinc yomoya yesibini eyakhiwe ngokwesiqhelo kwi-electrode emithathu, kunye noxinzelelo lwangoku, i-electrolyte molarity, ubushushu, ukucoceka kwe-oxygen. nayo ivavanyiwe.Iimpawu ze-ORR kunye ne-OERii-electrodes.Ekugqibeleni, ukuqina kwenkqubo ye-zinc-air yesibini kwavavanywa, kubonisa ukusebenza kwamandla ka-58-61% kwi-20 mA cm-2 kwi-4 M NaOH + 0.3 M ZnO kwi-333 K kwiiyure ze-40.
Iibhetri zomoya wesinyithi ezinee-electrode zeoksijini zithathwa njengeenkqubo ezinomtsalane kakhulu kuba izinto zombane ze-oxygen electrode zinokufumaneka lula kwiatmosfera engqongileyo kwaye azifuni kugcinwa1.Oku kwenza kube lula ukuyila inkqubo ngokuvumela i-electrode ye-oksijini ukuba ibe nomthamo ongenamkhawulo, ngaloo ndlela ikhulise ukuxinana kwamandla kwenkqubo.Ke ngoko, iibhetri zomoya wesinyithi ezisebenzisa izinto ze-anode ezifana ne-lithium, i-aluminium, intsimbi, i-zinc, kunye ne-magnesium ziye zavela ngenxa yomthamo wazo obalaseleyo.Phakathi kwazo, iibhetri zomoya we-zinc ziyakwazi ukuhlangabezana nemfuno yentengiso yeendleko, ukhuseleko, kunye nobuhlobo bendalo, kuba i-zinc ineempawu ezininzi ezinqwenelekayo njengesixhobo se-anode, ezinjengozinzo olufanelekileyo kwi-electrolyte enamanzi, ukuxinana kwamandla aphezulu, kunye nokulingana okuphantsi.amandla., ukuguqulwa kwe-electrochemical, ukuhanjiswa kakuhle kombane, ubuninzi kunye nokulula ukuphatha4,5.Okwangoku, nangona iibhetri zomoya ze-zinc eziphambili zisetyenziselwa kwizicelo zorhwebo ezifana nezixhobo zokuva, izibonakaliso zikaloliwe kunye nezibane zokuhamba, iibhetri zesibini ze-zinc zinamandla obuninzi bamandla obunokuthelekiswa neebhetri ezisekelwe kwi-lithium.Oku kwenza kube luncedo ukuqhubeka nophando kwiibhetri zomoya we-zinc kwizicelo kwi-electronics ephathekayo, izithuthi zombane, ukugcinwa kwamandla egridi kunye nokuxhasa ukuveliswa kwamandla avuselelekayo6,7.
Enye yeenjongo eziphambili kukuphucula ukusebenza kakuhle kweempendulo ze-oksijini kwi-electrode yomoya, oko kukuthi i-oxygen reduction reaction (ORR) kunye ne-oxygen evolution reaction (OER), ukwenzela ukukhuthaza ukuthengiswa kweebhetri zesibini ze-Zn-air.Ukuza kuthi ga ngoku, i-electrocatalysts esebenzayo ingasetyenziselwa ukunyusa izinga lokuphendula kwaye ngaloo ndlela yandise ukusebenza kakuhle.Okwangoku, i-oxygen electrodes ene-bifunctional catalysts ichazwe kakuhle kwiincwadi8,9,10.Nangona i-bifunctional catalysts inokwenza lula ukwakheka kwee-electrodes kunye nokunciphisa ilahleko yokudlulisa ubuninzi, enokunceda ukunciphisa iindleko zokuvelisa, ngokusebenza, ii-catalysts ezifanelekileyo kwi-ORR zihlala zingafanelekanga kwi-OER, kunye ne-vice versa11.Lo mahluko ekusebenzeni okusebenzayo kubangela ukuba i-catalyst ibonakaliswe kuluhlu olubanzi lwezinto ezinokubakho, ezinokutshintsha isakhiwo sayo somphezulu ngexesha.Ukongeza, ukuxhomekeka kwamanye amandla okubophelela okuphakathi kuthetha ukuba iisayithi ezisebenzayo kwi-catalyst zinokwahluka kwimpendulo nganye, enokuthi ibe nzima ukulungelelanisa.
Enye ingxaki enkulu kwiibhetri ze-Zn zesibini kuyilo lwe-oxygeni-electrode, ikakhulu ngenxa yokuba i-monofunctional catalysts ye-ORR kunye ne-OER isebenza kwiimidiya ezahlukeneyo zokusabela.I-ORR ye-gas diffusion layer kufuneka ibe yi-hydrophobic ukuvumela igesi ye-oksijini ukuba ingene kwiindawo ze-catalytic, ngelixa i-OER indawo ye-electrode kufuneka ibe yi-hydrophilic ukuze iququzelele ukukhutshwa kwe-oxygen bubbles.Kwikhiwane.I-1 ibonisa ezintathu eziqhelekileyo eziqhelekileyo ze-oxygen electrode designs ezithathwe kuhlaziyo nguJorissen12, ezizezi (i) i-catalysts ye-monolayer esebenzayo, (ii) i-catalysts ephindwe kabini okanye ye-multilayer, kunye (iii) nokucwangciswa kwe-electrode kathathu.
Kuyilo electrode yokuqala, equka kuphela umaleko enye bifunctional catalyst ukuba ngaxeshanye catalyzes ORR kunye OER, ukuba inwebu ibandakanyiwe kule uyilo, ngoko indibano inwebu-electrode (MEA) yenziwa njengoko kubonisiwe.Uhlobo lwesibini lubandakanya ezimbini (okanye ngaphezulu) iibhedi ze-catalyst kunye ne-porosity eyahlukeneyo kunye ne-hydrophobicity kwi-akhawunti yeeyantlukwano kwiindawo zokusabela13,14,15.Kwezinye iimeko, iibhedi ezimbini ze-catalytic ziyahlukana, kunye necala le-hydrophilic ye-OER ejongene ne-electrolyte kunye necala le-semi-hydrophobic ye-ORR ejongene neziphelo ezivulekileyo ze-electrode 16, 17, 18. iseli equkethe ezimbini reaction- i-electrodes ethile ye-oxygen kunye ne-zinc electrode19,20.Uluhlu lwe-S1 ludwelisa izinto ezilungileyo kunye nezingeloncedo kuyilo ngalunye.
Ukuphunyezwa koyilo lwe-electrode olwahlula i-ORR kunye ne-OER reactions ngaphambili lubonise ukuphuculwa kozinzo lokuhamba ngebhayisikile19.Oku kuyinyani ngakumbi kulungiselelo lwe-electrode emithathu, apho ukuthotywa kwe-catalysts engazinzanga kunye ne-co-additives kuncitshiswe kwaye ukuphuma kwegesi kulawulwa ngakumbi kulo lonke uluhlu olunokwenzeka.Ngenxa yezi zizathu, sasebenzisa i-electrode ye-Zn-air configuration emithathu kulo msebenzi.
Kweli nqaku, siqala ngokukhetha ii-catalysts ze-ORR ezisebenzayo ngokuthelekisa ii-oxide zetsimbi ezahlukeneyo zenguqu, izixhobo ze-carbonaceous, kunye ne-reference catalysts kunye novavanyo lwe-disk electrode (RDE).Ii-oksidi zetsimbi zenguqu zithande ukuba yi-electrocatalysts elungileyo ngenxa yeemeko zazo ezahlukeneyo ze-oxidation;Iimpendulo zenziwa lula ngakumbi kubukho bezi khompawundi21.Ngokomzekelo, i-manganese oxides, i-cobalt oxides, kunye ne-cobalt-based oxides exubeneyo (efana ne-NiCo2O4 kunye ne-MnCo2O4) i-22,23,24 ibonisa i-ORR enhle kwiimeko ze-alkaline ngenxa ye-d-orbitals egcwele isiqingatha, amanqanaba amandla e-electron avumela i-electron. umsebenzi kunye nokuphucula intuthuzelo yokusika.Ukongezelela, zininzi kakhulu kwindawo kwaye zine-conductivity eyamkelekileyo yombane, i-reactivity ephezulu kunye nokuzinza okulungileyo.Ngokufanayo, izinto ze-carbonaceous zisetyenziswa ngokubanzi, zineenzuzo zokuqhuba umbane ophezulu kunye nommandla omkhulu.Kwezinye iimeko, ii-heteroatoms ezifana ne-nitrogen, i-boron, i-phosphorus, kunye ne-sulfure ziye zaziswa kwikhabhoni ukuguqula isakhiwo sayo, ukuphucula ngakumbi iimpawu ze-ORR zezi zinto.
Ngokusekwe kwiziphumo zovavanyo, sifake ii-catalysts ze-OVR ezikhethiweyo kwi-gas diffusion electrode (GDE) kwaye sazivavanya kwiindawo ezahlukeneyo zokuxinana kwangoku.Eyona nto isebenzayo i-ORR GDE catalyst iye yadityaniswa kwisiko lethu lesithathu-electrode yesibini ibhetri ye-Zn-air kunye ne-reaction-specific OER electrode elungiselelwe kumsebenzi wethu wangaphambili26,27.Amandla ee-electrode ze-oksijini ngamnye abekwe iliso ngexesha lokukhutshwa okuqhubekayo kunye novavanyo lokukhwela ibhayisikile ukufunda umphumo weemeko zokusebenza ezifana nokuxinana kwangoku, i-electrolyte molarity, ubushushu bokusebenza kweeseli, kunye nokucoceka kwe-oksijini.Ekugqibeleni, ukuzinza kweebhetri zesibini ze-Zn-air kwavavanywa phantsi kwebhayisikili eqhubekayo phantsi kweemeko ezifanelekileyo zokusebenza.
I-MnOx28 yalungiswa nge-chemical redox method: 50 ml ye-0.04 M KMnO4 isisombululo (Fisher Scientific, 99%) yongezwa kwi-100 ml ye-0.03 Mn (CH3COO) 2 (Fisher Scientific, 98%) ukwenza imvula emdaka.Umxube ulungelelaniswe kwi-pH 12 kunye ne-dilute sodium hydroxide, emva koko i-centrifuged ngamaxesha angama-3-5 kwi-2500 rpm ukuqokelela i-precipitate.Imvula yayihlanjwa ngamanzi adiyiniweyo de umbala omfusa we-ion permanganate unyamalale.Ekugqibeleni, iidiphozithi zomiswa emoyeni kwi-333 K ngobusuku zaza zacolwa.
I-spinel oxides i-Co3O4, i-NiCo2O4, kunye ne-MnCo2O4 yenziwe ngokubola kwe-thermal.I-NiCo2O4 kunye ne-MnCo2O4 zalungiswa ngokudibanisa i-0.5 M (14.5 g) nickel (II) nitrate hexahydrate, Ni(NO3)2⋅6H2O (Fisher Scientific, 99.9%) okanye 0.5 M (12.6 g) tetrahydrate manganese(II) nitrate Mn(NO3) ).)2 4H2O (Sigma Aldrich, ≥ 97%) kunye ne-1 M (29.1 g) cobalt (II) nitrate hexahydrate, Co (NO3) 2 6H2O (Fisher Scientific, 98+%, ACS reagents) kwi-methanol (Fisher Scientific%, 99. ) kwi-100 ml ye-dilution vials.I-Methanol yongezwa kwiincinci ezincinci kwi-nitrate yensimbi yenguqu kunye nokuvuselela ngokuqhubekayo kuze kube yilapho isisombululo se-homogeneous sifunyenwe.Emva koko isisombululo sidluliselwe kwi-crucible kwaye sitshiswe kwisitya esishushu, sishiya ubumnyama obomvu obumnyama.Isiqina safakwa kwi-648 K nge-20 h emoyeni.Isiqina esifunyenweyo sagutywa sangumgubo ocolekileyo.Akukho Ni (NO3) 2 6H2O okanye Mn (NO3) 2 4H2O yongezwa ngexesha lokudityaniswa kweCo3O4.
Iinanosheets zeGraphene ezinomphezulu we-300 m2/g (Sigma Aldrich), igraphene efakwe initrogen (Sigma Aldrich), umgubo wekhabhoni omnyama (Vulcan XC-72R, Cabot Corp., 100%), MnO2 (Sigma Aldrich) kunye 5 wt.% Pt/C (Acros Organics) yasetyenziswa njengoko injalo.
Imilinganiselo ye-RDE (i-Pine Research Instrumentation) yayisetyenziselwa ukuvavanya umsebenzi wee-catalysts ezahlukeneyo ze-ORR kwi-1 M NaOH.I-inki ye-catalytic equkethe i-1 mg catalyst + 1 ml deionized (DI) H2O + 0.5 ml isopropanol (IPA) + 5 µl 5 wt% Nafion 117 (Sigma-Aldrich) isetyenziswe njengoko injalo.Xa i-Vulcan XC-72R yongezwa, ipeyinti ye-catalytic yayine-0.5 mg catalyst + 0.5 mg Vulcan XC-72R + 1 ml DI HO + 0.5 ml IPA + 5 µl 5 wt% Nafion 117 ukuqinisekisa ukulayishwa kwezinto eziphathekayo.Umxube wawufakwe kwi-sonicated imizuzu engama-20 kunye ne-homogenized usebenzisa i-Cole-Parmer LabGen 7 Series homogenizer kwi-28,000 rpm imizuzu emi-4.I-inki iye yasetyenziswa kwi-aliquots ezintathu ze-8 μl kumphezulu weglasi ye-electrode yeglasi (iPine Instrument Company) enobubanzi obuyi-4 mm (indawo yokusebenza ≈ 0.126 cm2) kwaye yomiswa phakathi kweeleya ukunika umthwalo we-≈120 μg cm. -2.Phakathi kwezicelo, i-glassy carbon electrode surface yayimanzi ngokulandelelanayo ipholishelwe nge-MicroCloth (Buehler) kunye ne-1.0 mm kunye ne-0.5 mm i-alumina powder (i-MicroPolish, i-Buehler) ilandelwa yi-sonication kwi-H2O ye-deionized.
Iisampuli ze-electrode ze-ORR zokusasazwa kwegesi zalungiswa ngokweprotocol28 yethu echazwe ngaphambili.Okokuqala, i-catalyst powder kunye ne-Vulcan XC-72R zixutywe kwi-1: 1 ubunzima besisindo.Emva koko umxube wesisombululo se-polytetrafluoroethylene (PTFE) (i-60 wt.% kwi-H2O) kunye ne-solvent enomlinganiselo we-IPA / H2O ye-1: 1 yongezwa kumxube owomileyo.I-Sonicate ipeyinti ye-catalytic malunga nemizuzu engama-20 kwaye i-homogenize malunga nemizuzu emi-4 kwi-28,000 rpm.I-inki yayisetyenziswa kancinci nge-spatula kwiphepha lekhabhoni elisikwe ngaphambili eli-13 mm ububanzi (AvCarb GDS 1120) kwaye yomiswa de kube umxholo we-catalyst we-2 mg cm2 ufikeleleke.
Ii-electrode ze-OER zenziwe nge-cathodic electrodeposition ye-Ni-Fe hydroxide catalysts kwi-15 mm x 15 mm yentsimbi engatyiwayo.umnatha(DeXmet Corp, 4SS 5-050) njengoko ingxelo26,27.I-Electrodeposition yenziwa kwi-standard three-electrode half-cell (i-polymer-coated glass cell cell of about 20 cm3) kunye ne-Pt grid njenge-counter electrode kunye ne-Hg / HgO kwi-1 M NaOH njenge-electrode reference.Vumela i-catalyst egqunywe ngomnatha wentsimbi engenasici ukuba yome emoyeni ngaphambi kokusika indawo emalunga ne-0.8 cm2 kunye ne-10 mm engqindilili ye-carbon steel punch.
Ukuthelekisa, i-ORR yorhwebo kunye ne-OER electrode zisetyenziswe njengoko zifunyenwe kwaye zavavanywa phantsi kweemeko ezifanayo.I-electrode ye-ORR yorhwebo (i-QSI Nano Gas Diffusion Electrode, i-Quantum Sphere, i-0.35 mm ubukhulu) iqulethe i-manganese kunye ne-carbon oxide efakwe umqokeleli wangoku we-nickel mesh, ngelixa i-electrode ye-OER yorhwebo (uhlobo 1.7, i-Magneto anode ekhethekileyo, i-BV) inobunzima be-1.3 mm.ukuya kuthi ga kwi-1.6 mm eyandisiweyo ye-titanium mesh eqatywe nge-Ru-Ir exutywe ngentsimbi ye-oxide.
Ukwakheka komphezulu kunye nokwakhiwa kwee-catalysts zibonakaliswe kusetyenziswa i-FEI Quanta 650 FEG yokuskena i-electron microscope (SEM) esebenza phantsi kwevacuum ephezulu kunye nombane okhawulezayo we-5 kV.Idatha ye-X-ray ye-powder diffraction (XRD) iqokelelwe kwi-Bruker D8 Advance X-ray diffractometer kunye nomthombo wetyhubhu yobhedu (λ = 1.5418 Å) kwaye ihlalutywe kusetyenziswa i-software ye-Bruker Diffraction Suite EVA.
Yonke imilinganiselo ye-electrochemical yenziwa kusetyenziswa i-Biologic SP-150 potentiostat kunye nesoftware ye-EC-lab.Iisampulu ze-RDE kunye ne-GDE zavavanywa kwi-standard three-electrode setup ebandakanya i-200 cm3 iseli yeglasi yebhatyi kunye ne-Laggin capillary njenge-electrode yereferensi.I-Pt mesh kunye ne-Hg / HgO kwi-1 M NaOH isetyenziswe njenge-counter and reference electrodes, ngokulandelanayo.
Kwimilinganiselo ye-RDE kumfuniselo ngamnye, i-electrolyte entsha ye-1 M NaOH isetyenzisiwe, iqondo lobushushu lagcinwa lingaguquki kwi-298 K kusetyenziswa ibhafu yamanzi ajikelezayo (TC120, Grant).Ioksijini yegesi (BOC) yayigruzuka kwi-electrolyte ngeglasi yefrit ene-porosity ye-25-50 µm ubuncinane imizuzu engama-30 phambi kovavanyo ngalunye.Ukufumana i-ORR i-polarization curves, i-potency yaskenwa ukusuka kwi-0.1 ukuya -0.5 V (ngokumalunga ne-Hg / HgO) kwinqanaba lokuskena kwe-5 mV s -1 kwi-400 rpm.I-voltammograms ye-cyclic yafunyanwa ngokutshayela amandla aphakathi kwe-0 kunye -1.0 V kunye ne-Hg / HgO ngesantya se-50 mV s-1.
Ngemilinganiselo ye-HDE, i-electrolyte ye-1 M NaOH igcinwe kwi-333 K kunye nebhafu yamanzi ejikelezayo.Indawo esebenzayo ye-0.8 cm2 ibonakaliswe kwi-electrolyte kunye nokubonelela ngokuqhubekayo kwe-oksijini ukuya kwicala elingasemva le-electrode ngesantya se-200 cm3 / min.Umgama omiselweyo phakathi kwe-electrode esebenzayo kunye ne-electrode yereferensi yayingu-10 mm, kwaye umgama phakathi kwe-electrode esebenzayo kunye ne-counter electrode yayingu-13-15 mm.Ucingo lwe-nickel kunye ne-mesh zibonelela ngoqhagamshelwano lombane kwicala legesi.Imilinganiselo yeChronopotentiometric ithathwe kwi-10, 20, 50 kunye ne-100 mA cm-2 ukuvavanya ukuzinza kunye nokusebenza kakuhle kwe-electrode.
Iimpawu ze-ORR kunye ne-OER electrode zavavanywa kwiseli yeglasi enejakethi eyi-200 cm3 kunye nokufakwa kwe-PTFE29.Umzobo wesicwangciso senkqubo uboniswe kuMfanekiso S1.I-electrode ekwibhetri idityaniswe kwinkqubo ye-electrode emithathu.I-electrode esebenzayo yayiquka i-reaction-specific ORR kunye ne-OER electrodes exhunywe kwimodyuli ye-relay (Ingoma, i-SRD-05VDC-SL-C) kunye ne-microcontroller (i-Raspberry Pi 2014 © imodeli ye-B + V1.2) ene-anode ye-zinc.njengesibini I-electrodes kunye ne-electrode yereferensi ye-Hg / HgO kwi-4 M NaOH yayikumgama we-3 mm ukusuka kwi-anode ye-zinc.Iskripthi sePython sibhaliwe ukuba sisebenze kwaye silawule iRaspberry Pi kunye neModyuli yoRelay.
Iseli yatshintshwa ukuze ifake i-anode ye-zinc foil (I-Goodfellow, i-1 mm ubukhulu, i-99.95%) kunye nekhava ye-polymer yavumela ukuba i-electrodes ibekwe kumgama oqingqiweyo malunga ne-10 m.4 mm ukuhlukana.Iiplagi zerabha ze-Nitrile zalungisa i-electrodes kwisiciko, kunye neengcingo zenickel (i-Alfa Aesar, i-0.5 mm ububanzi, i-annealed, i-99.5% ye-Ni) yayisetyenziselwa uqhagamshelwano lombane lwee-electrode.I-anode ye-zinc foil yacocwa kuqala nge-isopropanol kwaye emva koko ngamanzi adibeneyo, kwaye umphezulu we-foil wagqunywa nge-polypropylene tape (Avon, AVN9811060K, 25 µm ubukhulu) ukubonisa indawo esebenzayo emalunga ne-0.8 cm2.
Yonke imifuniselo yokuhamba ngebhayisikile yenziwe kwi-4 M NaOH + 0.3 M ZnO electrolyte kwi-333 K ngaphandle kokuba kuphawulwe ngenye indlela.Kulo mfanekiso, i-Ewe malunga ne-Hg / HgO ibhekisela kwikhono le-oxygen electrode (ORR kunye ne-OER), i-Ece malunga ne-Hg / HgO imele amandla e-zinc electrode, i-Ecell malunga ne-Hg / HgO imele ngokupheleleyo. iseli enokubakho okanye umahluko onokubakho.phakathi kwezinto ezimbini ezinokubakho zebhetri.I-oksijeni okanye umoya oxinyiweyo wanikezelwa kwicala elingasemva le-electrode ye-OPP kwinqanaba lokuhamba rhoqo le-200 cm3 / min.Ukuzinza kwebhayisikili kunye nokusebenza kwee-electrodes kufundwe ngokuxinwa kwangoku kwe-20 mA cm-2, ixesha lokujikeleza kwe-30 min, kunye nexesha lokuphumla kwe-OCV ye-1 iminithi phakathi komjikelezo wesiqingatha ngasinye.Ubuncinci bemijikelezo ye-10 yenziwa kuvavanyo ngalunye, kwaye idatha ikhutshwe kwimijikelezo ye-1, i-5, kunye ne-10 ukumisela imeko yee-electrodes ngexesha.
I-morphology ye-ORR catalyst ibonakaliswe yi-SEM (umzobo 2), kunye ne-powder X-ray imilinganiselo ye-diffraction iqinisekisa isakhiwo se-crystal yeesampuli (umzobo 3).Iiparamitha zesakhiwo seesampuli ze-catalyst zinikezelwa kwiThebhile 1. 1. Xa uthelekisa i-manganese oxides, i-MnO2 yorhwebo kwifig.I-2a iqukethe iinqununu ezinkulu, kunye nephethini ye-diffraction kwi-Fig. 3a ihambelana ne-JCPDS 24-0735 ye-tetragonal β-MnO2.Ngokuchasene noko, kwi-MnOx ebusweni kwi-Fig. 2b ibonisa iincinci ezincinci kunye nezincinci, ezihambelana nephethini ye-diffraction kwi-Fig. (541) ye-tetrahedral igxile kwi-α-MnO2 hydrate, i-JCPDS 44-014028.
(a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, (g) igraphene, (h) initrogen efakwe igraphene, (kunye) 5 wt .% Pt/C.
Iipateni zeX-reyi (a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, nitrogen-doped graphene kunye negraphene, kunye (g) 5 Ipesenti yeplatinam/carbon.
Kwikhiwane.I-2c-e, i-surface morphology ye-oxides esekelwe kwi-cobalt Co3O4, i-NiCo2O4, kunye ne-MnCo2O4 iqulethwe ngamaqoqo amaqhekeza angalinganiyo.Kwikhiwane.I-3c–e ibonisa ukuba zonke ezi nguqukointsimbii-oxides inesakhiwo se-spinel kunye nenkqubo ye-cubic crystal efanayo (JCPDS 01-1152, JCPDS 20-0781, kunye ne-JCPDS 23-1237, ngokulandelanayo).Oku kubonisa ukuba indlela yokuchithwa kwe-thermal iyakwazi ukuvelisa i-oxides ye-crystalline ye-crystalline ephezulu, njengoko kubonakaliswe ngamanqwanqwa anamandla achazwe kakuhle kwipatheni ye-diffraction.
Imifanekiso ye-SEM yezinto zekhabhoni ibonisa utshintsho olukhulu.Kwikhiwane.I-2f iVulcan XC-72R ikhabhoni emnyama iqulathe iinanoparticles ezixineneyo.Ngokuchasene noko, ukubonakala kwegraphene kwi-Fig.Nangona kunjalo, i-graphene ye-N-doped (Umfanekiso we-2h) ibonakala iqulethwe ngamaleko amancinci.Iipateni ezihambelanayo ze-X-ray diffraction ye-Vulcan XC-72R, i-graphene nanosheets yorhwebo, kunye ne-N-doped graphene kwiFigs.I-3f ibonisa utshintsho oluncinci kumaxabiso e-2θ ye-(002) kunye ne-(100) yeencopho zekhabhoni.I-Vulcan XC-72R ichongiwe njenge-graphite ye-hexagonal kwi-JCPDS 41-1487 kunye neencopho (002) kunye (100) ezibonakala kwi-24.5 ° kunye ne-43.2 ° ngokulandelanayo.Ngokufanayo, iincopho (002) kunye (100) ze-graphene ye-N-doped zivela kwi-26.7 ° kunye ne-43.3 °, ngokulandelanayo.Ubunzulu bemvelaphi obuqatshelwe kwiipatheni zokwahlukana kweX-reyi ye-Vulcan XC-72R kunye ne-nitrogen-doped graphene kungenxa yobume bokuphazamiseka kakhulu kwezi zixhobo kwi-morphology yazo yomphezulu.Ngokwahlukileyo, iphethini ye-diffraction ye-graphene nanosheets ibonisa i-peak ebukhali, i-peak (002) kwi-26.5 ° kunye ne-peak encinci ebanzi (100) kwi-44 °, ebonisa i-crystalline nature yale sampuli.
Ekugqibeleni, kumkhiwane.I-2i ye-SEM umfanekiso we-5 wt.% I-Pt / C ibonisa amaqhekeza ekhabhoni enziwe ngentonga ene-voids ejikelezayo.I-Cubic Pt inqunywe kwiinqununu ezininzi kwi-5 wt% ye-Pt / C iphethini ye-diffraction kwi-Fig. 3g, kwaye i-peak kwi-23 ° ihambelana ne-(002) ye-carbon ekhoyo.
I-linear sweep ORR catalyst voltammogram yarekhodwa ngesantya sokutshayela i-5 mV s-1.Ngenxa yokunciphisa ukuhanjiswa kobuninzi, iimephu eziqokelelweyo (umzobo 4a) ngokuqhelekileyo zinemilo ye-S eyandisa kwi-plateau enokubakho okubi ngakumbi.Uxinzelelo lwangoku olukhawulelayo, i-jL, i-E1/2 enokubakho (apho i-j/jL = ½) kunye nokuqala okunokwenzeka kwi--0.1 mA cm-2 kukhutshwe kwezi zakhiwo kwaye zidweliswe kwiThebhile 2. Kubalulekile ukuba uqaphele ukuba kwifig.I-4a, ii-catalysts zinokuhlelwa ngokwee-E1/2 zazo ezinokuthi zibe: (I) ii-oxide zetsimbi, (II) izinto ze-carbonaceous, kunye (III) nezinyithi ezihloniphekileyo.
I-Linear sweep voltammograms ye (a) i-catalyst kunye (b) nefilimu ebhityileyo ye-catalyst kunye ne-XC-72R, elinganiswe kwi-RDE glassy carbon probe kwi-400 rpm nge-scan rate ye-5 mV s-1 kwi-O2 saturation kwi-298 K kwi-1 M NaOH cf.
Iioksidi zentsimbi zomntu ngamnye we-Mn kunye ne-Co kwiqela ndibonisa amandla okuqala -0.17 V kunye -0.19 V ngokulandelelana, kunye nexabiso le-E1 / 2 liphakathi kwe -0.24 kunye ne -0.26 V. Iimpendulo zokunciphisa ezi oksidi zetsimbi ziboniswa kwi-equation. .(1) kunye (2), ebonakala ecaleni kwekhono lokuqala kwiFig.I-4a ifanise amandla asemgangathweni kwinqanaba lokuqala le-2e ye-ORR indlela engathanga ngqo kwi-equation.(3).
Iioksidi zesinyithi ezixubeneyo i-MnCo2O4 kunye ne-NiCo2O4 kwiqela elifanayo libonisa amandla okuqala alungiswe kancinci kwi -0.10 kunye -0.12 V ngokulandelelana, kodwa gcina ixabiso le-E1 / 2 malunga ne-10.−0.23 volts.
Izinto zekhabhoni zeQela le-II zibonisa amaxabiso e-E1/2 ancomekayo kunee-oxide zentsimbi zeqela.Izinto zeGraphene zinesakhono sokuqala -0.07 V kunye nexabiso le-E1/2 lika -0.11 V, ngelixa isakhono sokuqala kunye ne-E1/2 ye-72R Vulcan XC- ziyi -0.12V kunye -0.17V ngokulandelelanayo.Kwiqela le-III, i-5 wt% ye-Pt / C ibonise eyona nto ifanelekileyo yokuqala kwi-0.02 V, i-E1 / 2 ye-0.055 V, kunye nomda ophezulu kwi-0.4 V, ekubeni ukunciphisa i-oxygen kwenzeka ngokuxinwa kwangoku kwendlela ye-4e. .Kwakhona ine-E1 / 2 ephantsi kakhulu ngenxa ye-conductivity ephezulu ye-Pt / C kunye ne-kinetics eguqulwayo ye-ORR reaction.
Umzobo we-S2a ubonisa uhlalutyo lwethambeka lweTafel kwii-catalysts ezahlukeneyo.Ummandla olawulwa yi-kinetically we-5 wt.% Pt / C iqala kwi-0.02 V ngokubhekiselele kwi-Hg / HgO, ngelixa ummandla wee-oxide zetsimbi kunye nezinto zekhabhoni zikuluhlu lwezinto ezinokuthi zingabikho ukusuka -0.03 ukuya -0.1 V. Ixabiso le-slope i-Tafel Pt/C yi--63.5 mV ss–1, eqhelekileyo kwi-Pt kuxinzelelo oluphantsi lwangoku lwe-dE/d log i = -2.3 RT/F31.32 apho inyathelo lokumisela izinga libandakanya ukutshintshwa kweoksijini ukusuka kwi-physisorption ukuya kwi-physisorption. ikhemisorption33,34.Amaxabiso ethambeka eTafel kwizinto zekhabhoni akummandla ofanayo kunye nePt/C (-60 ukuya -70 mV div-1), ecebisa ukuba ezi zixhobo zineendlela ezifanayo zeORR.oxides zetsimbi ngabanye of Co kunye Mn ingxelo Tafel amathambeka ukusuka -110 ukuya -120 mV dec-1, nto leyo dE / d log i = -2.3 2RT / F, apho inqanaba-ukugqiba inyathelo yi-electron yokuqala.inyathelo lokutshintshela 35, 36. Amaxabiso aphezulu kancinane kwithambeka elirekhodiweyo kwimixube yeeoxide zesinyithi iNiCo2O4 kunye neMnCo2O4, malunga -170 mV dec-1, ibonisa ubukho be-OH- kunye ne-H2O ion kumphezulu weoksidi, ethintela ukufakwa kweoksijini kunye ukudluliselwa kwe-electron, ngaloo ndlela kuchaphazela ioksijini.indlela yokunciphisa 35.
I-Kutetsky-Levich (KL) equation yayisetyenziselwa ukumisela iiparamitha ze-kinetic reaction kwiisampuli ezahlukeneyo ze-catalyst ngaphandle kokudluliselwa okukhulu.kwinxaki.(4) Uxinaniso olulinganisiweyo lulonke lwangoku j sisimbuku soxinaniso lwangoku lokudluliselwa kwe-electron kunye nokudluliselwa kobuninzi.
ukusuka kwinxaki.(5) Uxinano lwangoku olulinganiselweyo lwe-jL lulungelelana nengcambu yesantya sokujikeleza.Ke ngoko, i-equation ye-KL.(6) ichaza igrafu yomgca ka-j−1 xa ithelekiswa ne-ω−1//2, apho indawo yokuhlangana ingu-jk kunye nokuthambeka kwegrafu ngu-K.
apho u-ν yi-kinematic viscosity ye-electrolyte 1 M NaOH (1.1 × 10–2 cm2 s–1)37, D yi-diffusion coefficient ye-O2 kwi-1 M NaOH (1.89 × 10–5 cm2 s–1)38, ω yi-rpm yisantya sokujikeleza, i-C yi-oxygen concentration kwisisombululo esikhulu (8.4 × 10-7 mol cm-3)38.
Qokelela iivoltammograms ezitshayelweyo ngomgca usebenzisa i-RDE kwi-100, 400, 900, 1600, kunye ne-2500 rpm.Amaxabiso athathwe kwi--0.4 V kummandla wokudluliselwa kobunzima obulinganiselweyo ukuze acwangcise umzobo we-KL, okt -j-1 ngokuphikisana ne-ω-1 //2 ye-catalyst (Fig. S3a).Sebenzisa iiequations.Kwii-equations (6) kunye (7), izalathi zokusebenza ze-catalyst, ezifana ne-kinetic current density ngaphandle kokuthathela ingqalelo imiphumo yokudluliselwa kobunzima jk, igqitywe kwindawo yokuhlangana kunye ne-axis y, kunye nenani le Ukudluliselwa kwe-electron kugqitywa yi-gradient K yegophe.Adweliswe kwitheyibhile yesi-2.
I-5 wt% ye-Pt / C kunye ne-XC-72R inexabiso eliphantsi kakhulu le-jk, ebonisa i-kinetics ekhawulezayo kwezi zixhobo.Nangona kunjalo, i-slope ye-XC-72R ijika iphantse kabini kwi-5 wt% Pt / C, ekulindeleke ukuba i-K ibonakaliswe inani lee-electron ezidluliselwe ngexesha lokunciphisa i-oksijini.Ngokwethiyori, icebo le-KL le-5 wt% Pt/C kufuneka lidlule kwimvelaphi engama-39 phantsi kweemeko zokudluliselwa kobunzima obulinganiselweyo, nangona kunjalo oku akujongwanga kuMzobo we-S3a, ephakamisa imida ye-kinetic okanye yokusabalalisa echaphazela iziphumo.Oku kungenxa yokuba uGarsani et al.I-40 ibonise ukuba ukungahambelani okuncinci kwi-topology kunye ne-morphology yeefilimu ze-Pt / C ze-catalytic kunokuchaphazela ukuchaneka kwemilinganiselo yomsebenzi we-ORR.Nangona kunjalo, ekubeni zonke iifilimu ze-catalyst zilungiswe ngendlela efanayo, nayiphi na impembelelo kwiziphumo kufuneka ifane kuzo zonke iisampuli.I-graphene KL cross point ye-≈ -0.13 mA-1 cm2 ithelekiseka naleyo ye-XC-72R, kodwa i- -0.20 mA-1 cm2 ye-cross point ye-N-doped graphene KL igrafu ibonisa ukuba ubuninzi bangoku bukhulu buxhomekeke amandla ombane kwi-catalytic converter.Oku kungenxa yokuba i-nitrogen doping yegraphene inciphisa ukuhanjiswa kombane kukonke, okukhokelela ekudluliselweni kwe-electron kancinane kinetics.Ngokwahlukileyo, ixabiso elipheleleyo le-K le-nitrogen-doped graphene lincinci kune-graphene kuba ubukho be-nitrogen bunceda ukudala iindawo ezisebenzayo ze-ORR41,42.
I-oxides esekelwe kwi-manganese, indawo ye-intersection yexabiso elikhulu kakhulu libonwa - 0.57 mA-1 cm2.Nangona kunjalo, ixabiso elipheleleyo le-K le-MnOx liphantsi kakhulu kunelo le-MnO2 kwaye lisondele kwi-5 wt%.I-%Pt/C.Iinombolo zodluliselo lwe-electron ziye zamiselwa ukuba zisondele.I-MnOx yi-4 kunye ne-MnO2 isondele kwi-2. Oku kuhambelana neziphumo ezipapashwe kwiincwadi, ezichaza ukuba inani lokudluliselwa kwe-electron kwindlela ye-α-MnO2 ORR yi-4, ngelixa i-β-MnO243 ngokuqhelekileyo ingaphantsi kwe-4. Ngaloo ndlela Ngaloo ndlela , iindlela ze-ORR zihluke kwiindlela ezahlukeneyo ze-polymorphic ze-catalysts ezisekelwe kwi-manganese oxide, nangona iireyithi zamanyathelo ekhemikhali zihlala zifana.Ngokukodwa, ii-catalysts ze-MnOx kunye ne-MnCo2O4 zinamanani okudluliselwa kwe-electron angaphezulu kancinane kune-4 ngenxa yokuba ukuncitshiswa kweeoksidi ze-manganese ezikhoyo kwezi zikhuseli kwenzeka ngaxeshanye kunye nokunciphisa i-oxygen.Kumsebenzi wangaphambili, sifumene ukuba ukunciphisa i-electrochemical ye-manganese oxide kwenzeka kwinqanaba elifanayo elinokubakho njengokunciphisa i-oksijini kwisisombululo esigcwele i-nitrogen28.Igalelo leempendulo zecala likhokelela kwinani elibaliweyo leelektroni ezingaphezu kwe-4.
I-intersection ye-Co3O4 yi-≈ -0.48 mA-1 cm2, engaphantsi kwe-negative kuneendlela ezimbini ze-manganese oxide, kunye nenombolo yokudluliselwa kwe-electron ebonakalayo igqitywe ngexabiso lika-K elilingana no-2. Ukutshintsha i-Ni kwi-NiCo2O4 kunye ne-Mn kwi-MnCo2O4 ngo-Co kukhokelela ekunciphiseni amaxabiso ngokupheleleyo K, nto leyo ebonisa ukuphucuka electron transfer kinetics kwi oxides metal exutyiweyo.
I-Carbon substrates yongezwa kwi-ORR ye-catalyst inki yokwandisa ukuhanjiswa kombane kunye nokuququzelela ukubunjwa komda wesigaba esithathu kwi-electrodes ye-gas diffusion.I-Vulcan-XC-72R ikhethwe ngenxa yexabiso layo eliphantsi, indawo enkulu yommandla we-250 m2 · g-1, kunye nokumelana okuphantsi kwe-0.08 ukuya kwi-1 Ω · cm44.45.Iploti ye-LSV yesampuli ye-catalyst exutywe ne-Vulcan XC-72R kwi-400 rpm iboniswe kuMfanekiso 1. 4b.Esona siphumo sicacileyo sokongeza i-Vulcan XC-72R kukunyusa uxinano lwangoku.Qaphela ukuba oku kubonakala ngakumbi kwii-oxide zetsimbi, kunye ne-0.60 mA cm-2 eyongezelelweyo ye-oxides yensimbi enye, i-0.40 mA cm-2 yee-oxide zetsimbi ezixubekileyo, kunye ne-0.28 mA cm-2 yegraphene kunye ne-doped graphene.N. Yongeza i-0.05 mA cm-2.−2.Ukongezwa kwe-Vulcan XC-72R kwi-inki ye-catalyst nayo ibangele utshintsho olulungileyo kwithuba lokuqala kunye ne-E1 / 2 ye-half-wave enokubakho kuzo zonke ii-catalysts ngaphandle kwegraphene.Olu tshintsho lunokuba ngumphumo onokwenzeka wokunyuka kokusetyenziswa kwendawo ye-electrochemical surface46 kunye nokuphuculwa koqhagamshelwano47 phakathi kweengqungquthela ze-catalyst kwi-Vulcan XC-72R exhaswayo.
Izicwangciso zeTafel ezihambelanayo kunye neeparitha zekinetic zale mixube ye-catalyst iboniswe kuMzobo S2b kunye neThebhile 3, ngokulandelanayo.Amaxabiso ethambeka eTafel ayefana neMnOx kunye negraphene izinto kunye nangaphandle kweXC-72R, ebonisa ukuba iindlela zabo zeORR azichaphazelekanga.Nangona kunjalo, i-cobalt-based oxides i-Co3O4, i-NiCo2O4 kunye ne-MnCo2O4 zinike amaxabiso amancinci amancinci e-Tafel ethambeka phakathi kwe-68 kunye ne-80 mV dec-1 ngokudibanisa ne-XC-72R ebonisa utshintsho kwindlela ye-ORR.Umzobo we-S3b ubonisa icebo le-KL kwisampulu ye-catalyst edibeneyo kunye ne-Vulcan XC-72R.Ngokubanzi, ukuhla kwamaxabiso apheleleyo e-jk kwabonwa kuzo zonke ii-catalysts ezixutywe ne-XC-72R.I-MnOx ibonise ukuhla okukhulu kwixabiso elipheleleyo le-jk nge-55 mA-1 cm2, ngelixa i-NiCo2O4 irekhoda ukuhla kwe-32 mA-1 cm-2, kwaye i-graphene ibonise ukuhla kuncinci nge-5 mA-1 cm2.Kunokugqitywa ukuba umphumo we-Vulcan XC-72R ekusebenzeni kwe-catalyst ukhawulelwe ngumsebenzi wokuqala we-catalyst ngokwe-OVR.
I-Vulcan XC-72R ayichaphazeli ixabiso le-K le-NiCo2O4, i-MnCo2O4, i-graphene, kunye ne-nitrogen-doped graphene.Nangona kunjalo, ixabiso le-K le-Co3O4 lehla kakhulu kunye nokongezwa kwe-Vulcan XC-72R, ebonisa ukwanda kwenani le-electron ezidluliselwe yi-ORR.Ukudibanisa okunjalo kwe-Co3O4 kunye namacandelo ekhabhoni kuye kwabikwa kwii-refs.48, 49. Ukungabikho kwenkxaso yekhabhoni, i-Co3O4 icingelwa ukuba ikhuthaze ukungafani kwe-HO2- ukuya kwi-O2 kunye ne-OH-50.51, ehambelana kakuhle ne-Co3O4's inombolo yokudlulisa i-electron malunga ne-2 kwiThebhile 2. Ngaloo ndlela, i I-adsorption yomzimba ye-Co3O4 kwii-carbon substrates kulindeleke ukuba ivelise i-2 + 2 ye-electron ezine-ORR indlela52 eyokuqala i-electroreduces i-O2 ukuya kwi-HO2- kwi-interface ye-Co3O4 catalyst kunye ne-Vulcan XC-72R (i-equation 1) kwaye emva koko i-HO2 - I- disproportionated ngokukhawuleza umphezulu oxide metal iguqulelwa O2 ilandelwa electroreduction.
Ngokwahlukileyo, ixabiso elipheleleyo le-K MnOx liye lanyuka kunye nokongezwa kwe-Vulcan XC-72R, emele ukuncipha kwenani lokudluliselwa kwe-electron ukusuka kwi-4.6 ukuya kwi-3.3 (iThebhile 3).Oku kungenxa yobukho beendawo ezimbini kwi-carbon catalyst composite yendlela ye-electron yamanqanaba amabini.Ukuncitshiswa kokuqala kwe-O2 ukuya kwi-HO2- kwenzeka ngokulula ngakumbi kwiinkxaso zekhabhoni, okukhokelela ekunyusweni kancinane kokukhetha kwindlela yee-electron ezimbini ze-ORR53.
Uzinzo lwe-catalyst luvandlakanywe kwi-GDE-half-cell kuluhlu loxinaniso lwangoku.Kwikhiwane.I-5 ibonisa izicwangciso ezinokubakho xa zithelekiswa nexesha le-GDE MnOx, i-MnCo2O4, i-NiCo2O4, i-graphene, kunye ne-nitrogen-doped graphene.I-MnOx ibonisa uzinzo olupheleleyo olulungileyo kunye nokusebenza kwe-ORR kwindawo ephantsi kunye nephezulu yoxinaniso lwangoku, iphakamisa ukuba ilungele ukuphuculwa ngakumbi.
I-Chronopotentiometry yeesampuli ze-HDE okwangoku ukusuka kwi-10 ukuya kwi-100 mA / cm2 kwi-1 M NaOH, 333 K, i-O2 isantya sokuhamba kwe-200 cm3 / min.
I-MnCo2O4 nayo ibonakala igcina uzinzo lwe-ORR olulungileyo kulo lonke uluhlu lwangoku loxinaniso, kodwa kuxinzelelo oluphezulu lwangoku lwe-50 kunye ne-100 mA cm-2 ukugqithiswa kwe-overvoltage enkulu kuyabonwa ebonisa ukuba i-MnCo2O4 ayisebenzi kakuhle njenge-MnOx.I-Graphene GDE ibonisa owona msebenzi uphantsi we-ORR phezu koluhlu lwangoku loxinaniso oluvavanyiweyo, lubonisa ukwehla ngokukhawuleza kwentsebenzo kwi-100 mA cm-2.Ngoko ke, phantsi kweemeko zovavanyo ezikhethiweyo, i-MnOx GDE yakhethwa kwiimvavanyo ezongezelelweyo kwinkqubo yesibini ye-Zn-air.