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Kev ua tau zoo, pheej yig thiab ruaj khov oxygen txo cov tshuaj tiv thaiv (ORR) electrocatalysts yog qhov tseem ceeb rau cov roj teeb Zn-air thib ob.Kev ua haujlwm ORR ntawm ib leeg thiab sib xyaw hlau oxides thiab cov pa roj carbon electrocatalysts tau tshawb xyuas los ntawm kev ntsuas kev sib hloov disk electrode (RDE), Tafel slopes, thiab Kutetsky-Levich cov phiaj xwm.Nws tau pom tias kev sib xyaw ntawm MnOx thiab XC-72R nthuav tawm cov haujlwm siab PBP thiab kev ruaj ntseg zoo, txog li 100 mA cm-2.Kev ua tau zoo ntawm ORR electrodes thiab qhov ua tau zoo ntawm cov pa oxygen evolution yav dhau los (OER) electrode tau sim hauv cov khoom siv hluav taws xob uas tsim los ntawm zinc-air roj teeb nyob rau hauv peb-electrode configuration, thiab tam sim no ceev, electrolyte molarity, kub, oxygen purity tau. kuj kuaj.Cov yam ntxwv ntawm ORR thiab OERelectrodes.Thaum kawg, qhov durability ntawm cov zinc-cua tshuab theem nrab tau soj ntsuam, ua kom pom lub zog ua haujlwm ntawm 58-61% ntawm 20 mA cm-2 hauv 4 M NaOH + 0.3 M ZnO ntawm 333 K rau 40 teev.
Cov roj teeb hlau-cua nrog oxygen electrodes yog suav tias yog cov tshuab zoo nkauj heev vim tias cov khoom siv hluav taws xob rau cov pa hluav taws xob tuaj yeem yooj yim tau los ntawm cov cua nyob ib puag ncig thiab tsis tas yuav khaws cia1.Qhov no ua kom yooj yim rau kev tsim qauv los ntawm kev tso cai rau cov pa oxygen electrode kom muaj peev xwm tsis muaj peev xwm, yog li ua kom lub zog ceev ntawm lub cev.Yog li ntawd, cov roj teeb hlau-cua siv cov khoom siv anode xws li lithium, txhuas, hlau, zinc, thiab magnesium tau tshwm sim vim lawv lub peev xwm tshwj xeeb.Ntawm lawv, zinc cua roj teeb muaj peev xwm ua tau raws li kev lag luam xav tau rau tus nqi, kev nyab xeeb, thiab ib puag ncig tus phooj ywg, txij li zinc muaj ntau yam kev xav tau raws li cov khoom siv anode, xws li kev ruaj ntseg zoo hauv aqueous electrolytes, siab zog ceev, thiab qis sib npaug.muaj peev xwm., electrochemical reversibility, zoo hluav taws xob conductivity, abundance thiab yooj yim ntawm tuav4,5.Tam sim no, txawm hais tias thawj zinc cua roj teeb tau siv rau hauv kev lag luam siv xws li cov khoom siv hnov ​​​​lus, railway signals thiab navigation lights, Secondary zinc air batteries muaj peev xwm ua kom muaj zog ceev piv rau lithium-based roj teeb.Qhov no ua rau nws tsim nyog rau kev tshawb fawb txuas ntxiv ntawm zinc cua roj teeb rau cov ntawv thov hauv cov khoom siv hluav taws xob portable, hluav taws xob tsheb, daim phiaj hluav taws xob txuag hluav taws xob thiab txhawb nqa hluav taws xob txuas ntxiv 6,7.
Ib lub hom phiaj tseem ceeb yog txhawm rau txhim kho kev ua haujlwm ntawm cov pa oxygen ntawm cov pa hluav taws xob, uas yog cov tshuaj tiv thaiv oxygen txo qis (ORR) thiab cov tshuaj tiv thaiv oxygen evolution (OER), txhawm rau txhawb kev lag luam ntawm cov roj teeb Zn-air thib ob.Txog rau qhov kawg no, cov khoom siv hluav taws xob muaj txiaj ntsig tuaj yeem siv los ua kom cov tshuaj tiv thaiv thiab yog li ua kom muaj txiaj ntsig zoo.Tam sim no, oxygen electrodes nrog bifunctional catalysts tau piav qhia zoo nyob rau hauv cov ntaub ntawv 8,9,10.Txawm hais tias bifunctional catalysts tuaj yeem ua kom yooj yim rau cov qauv ntawm electrodes thiab txo cov kev hloov pauv loj, uas tuaj yeem pab txo cov nqi tsim khoom, hauv kev xyaum, cov catalysts uas zoo tshaj plaws rau ORR feem ntau tsis haum rau OER, thiab vice versa11.Qhov sib txawv ntawm kev khiav hauj lwm muaj peev xwm ua rau cov catalyst raug nthuav tawm rau ntau qhov kev muaj peev xwm, uas tuaj yeem hloov nws cov qauv saum npoo ntawm lub sijhawm.Tsis tas li ntawd, kev sib koom ua ke ntawm kev sib txuas nruab nrab ntawm cov khoom siv hluav taws xob txhais tau hais tias cov chaw ua haujlwm ntawm cov catalyst tuaj yeem sib txawv rau txhua qhov kev tawm tsam, uas tuaj yeem cuam tshuam kev ua kom zoo dua qub.
Lwm qhov teeb meem loj rau cov roj teeb Zn-air thib ob yog kev tsim cov pa oxygenelectrode, feem ntau yog vim cov monofunctional catalysts rau ORR thiab OER ua haujlwm nyob rau hauv cov tshuaj tiv thaiv sib txawv.ORR gas diffusion txheej yuav tsum yog hydrophobic kom tso pa oxygen nkag mus rau hauv cov chaw catalytic, thaum OER lub electrode nto yuav tsum yog hydrophilic los pab tshem tawm cov npuas npuas.Ntawm daim duab.1 qhia txog peb qhov qauv ntawm cov pa oxygen electrode tsim los ntawm kev tshuaj xyuas los ntawm Jorissen12, uas yog (i) bifunctional monolayer catalysts, (ii) ob lossis ntau txheej catalysts, thiab (iii) triple electrode configurations.
Rau thawj electrode tsim, uas suav nrog tsuas yog ib txheej txheej bifunctional catalyst ib txhij catalyzes ORR thiab OER, yog hais tias ib daim nyias nyias muaj nyob rau hauv qhov tsim no, ces ib tug membrane-electrode los ua ke (MEA) yog tsim raws li qhia.Hom thib ob suav nrog ob (lossis ntau dua) lub txaj catalyst nrog qhov sib txawv porosity thiab hydrophobicity kom suav nrog qhov sib txawv ntawm cov tshuaj tiv thaiv zones13,14,15.Qee zaum, ob lub txaj catalytic tau sib cais, nrog rau sab hydrophilic ntawm OER ntsib cov electrolyte thiab semi-hydrophobic sab ntawm ORR ntsib qhov qhib kawg ntawm cov electrodes 16, 17, 18. ib lub xovtooj ntawm ob lub tshuaj tiv thaiv- tshwj xeeb oxygen electrodes thiab zinc electrode19,20.Table S1 teev qhov zoo thiab qhov tsis zoo ntawm txhua tus qauv tsim.
Qhov kev siv ntawm ib qho kev tsim hluav taws xob uas sib cais ORR thiab OER cov tshuaj tiv thaiv yav dhau los tau qhia txog kev txhim kho kev caij tsheb kauj vab19.Qhov no yog qhov tseeb tshwj xeeb tshaj yog rau peb qhov kev teeb tsa electrode, qhov twg degradation ntawm cov catalysts tsis ruaj khov thiab co-additives raug txo qis thiab outgassing yog tswj tau ntau dua ntawm tag nrho cov peev txheej.Rau cov laj thawj no, peb siv peb-electrode Zn-air configuration hauv txoj haujlwm no.
Hauv tsab xov xwm no, peb thawj zaug xaiv cov kev ua haujlwm siab ORR catalysts los ntawm kev sib piv ntau yam kev hloov pauv hlau oxides, cov ntaub ntawv carbonaceous, thiab cov khoom siv catalysts nrog rotating disk electrode (RDE) thwmsim.Hloov cov hlau oxides zoo li yuav zoo electrocatalysts vim lawv txawv oxidation xeev;Cov tshuaj tiv thaiv tau yooj yim dua catalyzed nyob rau hauv lub xub ntiag ntawm cov compounds21.Piv txwv li, manganese oxides, cobalt oxides, thiab cobalt-raws li sib xyaw oxides (xws li NiCo2O4 thiab MnCo2O4) 22,23,24 qhia zoo ORR nyob rau hauv alkaline tej yam kev mob vim lawv ib nrab-filled d-orbitals, electron zog theem uas tso cai rau electron. ua hauj lwm thiab txhim kho txiav kev nplij siab.Tsis tas li ntawd, lawv muaj ntau dua nyob rau hauv ib puag ncig thiab muaj cov khoom siv hluav taws xob siv tau zoo, muaj zog reactivity thiab zoo stability.Ib yam li ntawd, cov ntaub ntawv carbonaceous tau siv dav, muaj qhov zoo ntawm cov hluav taws xob hluav taws xob siab thiab thaj chaw loj.Qee zaum, heteroatoms xws li nitrogen, boron, phosphorus, thiab sulfur tau nkag mus rau hauv carbon los hloov nws cov qauv, ntxiv txhim kho ORR yam ntxwv ntawm cov ntaub ntawv no.
Raws li cov txiaj ntsig kev sim, peb suav nrog OVR cov khoom siv hluav taws xob xaiv hauv cov pa hluav taws xob diffusion electrodes (GDE) thiab sim lawv ntawm ntau qhov ceev tam sim no.Qhov ua tau zoo tshaj plaws ORR GDE catalyst tau sib sau ua ke rau hauv peb cov kev cai peb-electrode thib ob Zn-air roj teeb nrog rau cov tshuaj tiv thaiv tshwj xeeb OER electrodes optimized hauv peb cov haujlwm dhau los26,27.Lub peev xwm ntawm tus kheej cov pa oxygen electrodes tau saib xyuas thaum lub sij hawm tso tawm tas mus li thiab them nqi kev sim kev sim los kawm txog cov txiaj ntsig ntawm kev ua haujlwm xws li tam sim no ceev, electrolyte molarity, cell khiav hauj lwm kub, thiab oxygen purity.Thaum kawg, kev ruaj ntseg ntawm Zn-air Secondary roj teeb tau raug soj ntsuam nyob rau hauv kev sib tw mus tas li nyob rau hauv kev ua haujlwm zoo.
MnOx28 tau npaj los ntawm chemical redox method: 50 ml ntawm 0.04 M KMnO4 tov (Fisher Scientific, 99%) tau ntxiv rau 100 ml ntawm 0.03 M Mn (CH3COO)2 (Fisher Scientific, 98%) los tsim cov xim av precipitate.Cov sib tov yog hloov mus rau pH 12 nrog dilute sodium hydroxide, ces centrifuged 3-5 zaug ntawm 2500 rpm kom sau cov precipitate.Tom qab ntawd lub precipitate yog ntxuav nrog dej deionized kom txog thaum cov xim liab ntawm cov poov tshuaj permanganate ploj.Thaum kawg, cov deposits tau qhuav ntawm 333 K ib hmos thiab ces pulverized.
Spinel oxides Co3O4, NiCo2O4, thiab MnCo2O4 tau tsim los ntawm thermal decomposition.NiCo2O4 thiab MnCo2O4 tau npaj los ntawm kev ntxiv 0.5 M (14.5 g) npib tsib xee (II) nitrate hexahydrate, Ni(NO3) 2⋅6H2O (Fisher Scientific, 99.9%) lossis 0.5 M (12.6 g) tetrahydrate manganese (II) nitrate (II) nitrate. ).2 4H2O (Sigma Aldrich, ≥ 97%) thiab 1 M (29.1 g) cobalt (II) nitrate hexahydrate, Co(NO3)2 6H2O (Fisher Scientific, 98+%, ACS reagents) hauv methanol (Fisher Scientific, 99.9%) ) hauv 100 ml dilution vials.Methanol yog ntxiv rau hauv me me rau qhov kev hloov pauv hlau nitrate nrog txuas ntxiv mus kom txog thaum tau txais cov tshuaj homogeneous.Tom qab ntawd cov tshuaj tau hloov mus rau lub crucible thiab rhuab rau ntawm ib lub phaj kub, tawm hauv cov khoom liab tsaus.Cov khoom tau calcined ntawm 648 K rau 20 teev hauv huab cua.Tom qab ntawd lub resulting sib tov yog muab tso rau hauv ib tug zoo hmoov.Tsis muaj Ni(NO3)2 6H2O los yog Mn(NO3)2 4H2O tau ntxiv thaum lub sij hawm synthesis ntawm Co3O4.
Graphene nanosheets nrog thaj tsam ntawm 300 m2 / g (Sigma Aldrich), graphene doped nrog nitrogen (Sigma Aldrich), carbon dub hmoov (Vulcan XC-72R, Cabot Corp., 100%), MnO2 (Sigma Aldrich) thiab 5 wt.% Pt/C (Acros Organics) tau siv raws li yog.
Kev ntsuas RDE (Pine Research Instrumentation) tau siv los ntsuas cov haujlwm ntawm ntau yam ORR catalysts hauv 1 M NaOH.Ib tug catalytic number case uas muaj 1 mg catalyst + 1 ml deionized (DI) H2O + 0.5 ml isopropanol (IPA) + 5 µl 5 wt% Nafion 117 (Sigma-Aldrich) tau siv raws li yog.Thaum Vulcan XC-72R ntxiv, cov xim catalytic muaj 0.5 mg catalyst + 0.5 mg Vulcan XC-72R + 1 ml DI HO + 0.5 ml IPA + 5 µl 5 wt% Nafion 117 kom ntseeg tau tias cov khoom siv sib xws.Cov sib tov yog sonicated rau 20 feeb thiab homogenized siv ib tug Cole-Parmer LabGen 7 Series homogenizer ntawm 28,000 rpm rau 4 feeb.Tom qab ntawd tus number case tau muab tso rau hauv peb aliquots ntawm 8 μl rau saum npoo ntawm iav carbon electrode (Pine Instrument Company) nrog ib txoj kab uas hla ntawm 4 hli (chaw ua hauj lwm cheeb tsam ≈ 0.126 cm2) thiab qhuav ntawm cov khaubncaws sab nraud povtseg los muab ib tug load ntawm ≈120 μg cm. -2.Nyob nruab nrab ntawm daim ntawv thov, cov iav carbon electrode nto tau ntub ntub polished nrog MicroCloth (Buehler) thiab 1.0 hli thiab 0.5 hli alumina hmoov (MicroPolish, Buehler) ua raws li sonication hauv deionized H2O.
ORR gas diffusion electrode kuaj tau npaj raws li peb tau piav qhia yav dhau los raws tu qauv 28.Ua ntej, cov hmoov catalyst thiab Vulcan XC-72R tau sib xyaw hauv 1: 1 qhov hnyav piv.Tom qab ntawd sib tov ntawm ib qho kev daws ntawm polytetrafluoroethylene (PTFE) (60 wt.% hauv H2O) thiab cov kuab tshuaj nrog qhov sib piv ntawm IPA / H2O ntawm 1: 1 tau ntxiv rau cov hmoov qhuav qhuav.Sonicate cov xim catalytic li 20 feeb thiab homogenize li 4 feeb ntawm 28,000 rpm.Tom qab ntawd, tus number case yog thinly thov nrog lub spatula mus rau pre-cut carbon ntawv 13 mm inch (AvCarb GDS 1120) thiab qhuav kom txog thaum ib tug catalyst ntsiab lus ntawm 2 mg cm2.
OER electrodes tau tsim los ntawm cathodic electrodeposition ntawm Ni-Fe hydroxide catalysts mus rau 15 mm x 15 mm stainless hlaumesh(DeXmet Corp, 4SS 5-050) raws li qhia 26,27.Electrodeposition tau ua nyob rau hauv tus qauv peb-electrode ib nrab ntawm tes (polymer-coated iav cell ntawm kwv yees li 20 cm3) nrog Pt kab sib chaws ua lub txee electrode thiab Hg / HgO hauv 1 M NaOH raws li kev siv electrode.Cia lub catalyst coated stainless hlau mesh kom cua qhuav ua ntej txiav tawm thaj tsam ntawm kwv yees li 0.8 cm2 nrog 10 hli tuab carbon steel punch.
Rau kev sib piv, kev lag luam ORR thiab OER electrodes tau siv raws li tau txais thiab sim nyob rau hauv tib yam kev mob.Kev lag luam ORR electrode (QSI Nano Gas Diffusion Electrode, Quantum Sphere, 0.35 mm tuab) muaj manganese thiab carbon oxide coated nrog nickel mesh tam sim no collector, thaum lub lag luam OER electrode (hom 1.7, tshwj xeeb Magneto anode, BV) muaj thickness 1.3 mm.mus txog 1.6 hli nthuav titanium mesh coated nrog Ru-Ir tov hlau oxide.
Qhov saum npoo morphology thiab muaj pes tsawg leeg ntawm cov catalysts tau siv lub FEI Quanta 650 FEG scanning electron microscope (SEM) ua haujlwm nyob rau hauv lub tshuab nqus tsev siab thiab lub zog nrawm ntawm 5 kV.Powder X-ray diffraction (XRD) cov ntaub ntawv tau sau rau ntawm Bruker D8 Advance X-ray diffractometer nrog lub raj tooj liab (λ = 1.5418 Å) thiab tshuaj xyuas siv Bruker Diffraction Suite EVA software.
Txhua qhov kev ntsuas electrochemical tau ua tiav siv Biologic SP-150 potentiostat thiab EC-lab software.Cov qauv ntawm RDE thiab GDE tau raug kuaj ntawm tus qauv peb-electrode teeb uas muaj 200 cm3 tsho tsho iav cell thiab Laggin capillary raws li kev siv electrode.Pt mesh thiab Hg / HgO hauv 1 M NaOH tau siv los ua cov txee thiab siv electrodes, feem.
Rau kev ntsuas RDE hauv txhua qhov kev sim, tshiab 1 M NaOH electrolyte tau siv, qhov kub thiab txias uas tau khaws cia tas li ntawm 298 K siv cov dej da dej (TC120, Grant).Gaseous oxygen (BOC) tau bubbling rau hauv cov electrolyte los ntawm iav frit nrog ib tug porosity ntawm 25-50 µm rau yam tsawg 30 min ua ntej txhua yam kev sim.Kom tau txais ORR polarization curves, lub peev xwm tau luam tawm los ntawm 0.1 txog -0.5 V (kwv yees rau Hg / HgO) ntawm tus nqi scan ntawm 5 mV s -1 ntawm 400 rpm.Cyclic voltammograms tau txais los ntawm cheb lub peev xwm ntawm 0 thiab -1.0 V thiab Hg / HgO ntawm tus nqi ntawm 50 mV s-1.
Rau kev ntsuas HDE, 1 M NaOH electrolyte tau khaws cia ntawm 333 K nrog cov dej da dej.Ib qho chaw ua haujlwm ntawm 0.8 cm2 tau raug rau cov electrolyte nrog cov khoom siv txuas ntxiv ntawm oxygen mus rau sab nraub qaum ntawm cov electrode ntawm tus nqi ntawm 200 cm3 / min.Qhov kev ncua deb ntawm cov electrode ua hauj lwm thiab cov ntaub ntawv siv electrode yog 10 hli, thiab qhov kev ncua deb ntawm cov electrode ua hauj lwm thiab lub txee electrode yog 13-15 hli.Nickel hlau thiab mesh muab hluav taws xob tiv tauj rau sab roj.Chronopotentiometric ntsuas tau raug coj los ntawm 10, 20, 50 thiab 100 mA cm-2 los ntsuas qhov ruaj khov thiab kev ua haujlwm ntawm cov electrode.
Cov yam ntxwv ntawm ORR thiab OER electrodes tau soj ntsuam nyob rau hauv 200 cm3 jacketed iav cell nrog PTFE29 ntxig.Daim duab schematic ntawm lub kaw lus tau pom hauv daim duab S1.Cov electrodes nyob rau hauv lub roj teeb yog txuas nrog peb-electrode system.Lub tshuab hluav taws xob ua haujlwm muaj cais cov tshuaj tiv thaiv tshwj xeeb ORR thiab OER electrodes txuas nrog lub relay module (Songle, SRD-05VDC-SL-C) thiab microcontroller (Raspberry Pi 2014 © qauv B + V1.2) nrog zinc anode.Raws li ib khub Cov electrodes thiab cov ntaub ntawv siv electrode Hg / HgO hauv 4 M NaOH nyob ntawm qhov deb ntawm 3 hli los ntawm zinc anode.Ib tsab ntawv Python tau raug sau los ua haujlwm thiab tswj Raspberry Pi thiab Relay Module.
Lub xovtooj tau hloov kho kom haum rau zinc foil anode (Goodfellow, 1 mm tuab, 99.95%) thiab lub npog polymer tso cai rau cov electrodes muab tso rau ntawm qhov kev ncua deb ntawm kwv yees li 10 m.4mm sib.Nitrile roj hmab plugs kho cov electrodes nyob rau hauv lub hau, thiab nickel xov hlau (Alfa Aesar, 0.5 mm inch, annealed, 99.5% Ni) yog siv rau cov hluav taws xob tiv tauj ntawm cov electrodes.Zinc foil anode yog thawj zaug ntxuav nrog isopropanol thiab tom qab ntawd nrog dej deionized, thiab cov ntaub ntawv saum npoo tau npog nrog polypropylene daim kab xev (Avon, AVN9811060K, 25 µm tuab) kom nthuav tawm thaj tsam ntawm thaj tsam li ntawm 0.8 cm2.
Txhua qhov kev sim kev caij tsheb kauj vab tau ua nyob rau hauv 4 M NaOH + 0.3 M ZnO electrolyte ntawm 333 K tshwj tsis yog tau sau tseg.Hauv daim duab, Ewe hais txog Hg / HgO hais txog lub peev xwm ntawm oxygen electrode (ORR thiab OER), Ece nrog rau Hg / HgO sawv cev rau lub peev xwm ntawm zinc electrode, Ecell nrog rau Hg / HgO sawv cev tag nrho. cell muaj peev xwm lossis muaj peev xwm sib txawv.nruab nrab ntawm ob lub roj teeb muaj peev xwm.Cov pa oxygen lossis compressed cua tau nkag mus rau sab nraub qaum ntawm OPP electrode ntawm tus nqi ntws tsis tu ncua ntawm 200 cm3 / min.Lub voj voog kev ruaj ntseg thiab kev ua tau zoo ntawm cov electrodes tau kawm ntawm qhov ceev tam sim no ntawm 20 mA cm-2, lub sijhawm voj voog ntawm 30 min, thiab OCV lub sijhawm so ntawm 1 min ntawm txhua lub voj voog ib nrab.Yam tsawg kawg ntawm 10 lub voj voog tau ua rau txhua qhov kev sim, thiab cov ntaub ntawv tau muab rho tawm los ntawm lub voj voog 1, 5, thiab 10 los txiav txim seb qhov xwm txheej ntawm cov electrodes dhau sijhawm.
Lub morphology ntawm ORR catalyst yog tus cwj pwm los ntawm SEM (Fig. 2), thiab hmoov X-ray diffraction ntsuas tau lees paub cov qauv siv lead ua ntawm cov qauv (Fig. 3).Cov qauv tsis sib xws ntawm cov qauv catalyst tau muab rau hauv Table 1. 1. Thaum muab piv rau manganese oxides, kev lag luam MnO2 hauv daim duab.2a muaj cov khoom loj, thiab cov qauv diffraction hauv daim duab 3a sib raug rau JCPDS 24-0735 rau tetragonal β-MnO2.Ntawm qhov tsis sib xws, ntawm MnOx nto hauv daim duab 2b qhia cov khoom zoo dua thiab zoo dua, uas sib haum rau cov qauv diffraction hauv daim duab 66 ° sib haum rau cov peaks (110), (220), (310), (211), thiab (541) ntawm tetrahedrally centered α-MnO2 hydrate, JCPDS 44-014028.
(a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, (g) graphene, (h) nitrogen doped graphene, (thiab ) 5 wt .% Pt/C.
X-ray qauv ntawm (a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, nitrogen-doped graphene thiab graphene, thiab (g) 5 % platinum / carbon.
Ntawm daim duab.2c-e, qhov chaw morphology ntawm oxides raws li cobalt Co3O4, NiCo2O4, thiab MnCo2O4 muaj pawg ntawm cov khoom tsis sib xws.Ntawm daim duab.3c-e qhia tias tag nrho cov kev hloov pauv nohlauoxides muaj ib tug spinel qauv thiab ib tug zoo xws li cubic siv lead ua system (JCPDS 01-1152, JCPDS 20-0781, thiab JCPDS 23-1237, feem).Qhov no qhia tau hais tias cov txheej txheem thermal decomposition muaj peev xwm ua tau zoo heev crystalline hlau oxides, raws li pov thawj los ntawm cov muaj zog zoo-txhais ncov nyob rau hauv tus qauv diffraction.
SEM cov duab ntawm cov ntaub ntawv carbon qhia kev hloov loj.Ntawm daim duab.2f Vulcan XC-72R carbon dub muaj cov khoom ntim nanoparticles ntom ntom.Ntawm qhov tsis sib xws, cov tsos ntawm graphene hauv daim duab 2g yog cov phaj siab heev nrog qee cov agglomeration.Txawm li cas los xij, N-doped graphene (Fig. 2h) zoo nkaus li muaj cov txheej nyias nyias.Qhov sib thooj X-ray diffraction qauv ntawm Vulcan XC-72R, coj mus muag graphene nanosheets, thiab N-doped graphene hauv daim duab.3f qhia cov kev hloov me me hauv 2θ qhov tseem ceeb ntawm (002) thiab (100) carbon peaks.Vulcan XC-72R tau txheeb xyuas tias yog hexagonal graphite hauv JCPDS 41-1487 nrog peaks (002) thiab (100) tshwm sim ntawm 24.5 ° thiab 43.2 ° raws li.Ib yam li ntawd, qhov (002) thiab (100) ncov ntawm N-doped graphene tshwm sim ntawm 26.7 ° thiab 43.3 °, feem.Qhov kev siv ntawm keeb kwm yav dhau tau pom nyob rau hauv X-ray diffraction qauv ntawm Vulcan XC-72R thiab nitrogen-doped graphene yog vim muaj qhov tsis zoo ntawm cov ntaub ntawv no hauv lawv qhov chaw morphology.Nyob rau hauv sib piv, tus qauv diffraction ntawm graphene nanosheets qhia ib tug ntse, khaus ncov (002) ntawm 26.5 ° thiab ib tug me me sab ncov (100) ntawm 44 °, qhia ib tug ntau crystalline xwm ntawm cov qauv no.
Thaum kawg, hauv daim duab.2i SEM duab ntawm 5 wt.% Pt/C qhia cov pas nrig-zoo li cov pa roj carbon fragments nrog puag ncig voids.Cubic Pt yog txiav txim siab los ntawm feem ntau ntawm cov peaks nyob rau hauv 5 wt% Pt / C diffraction qauv hauv daim duab 3g, thiab lub ncov ntawm 23 ° sib haum mus rau (002) ncov ntawm cov pa roj carbon tam sim no.
Ib txoj kab cheb ORR catalyst voltammogram raug kaw ntawm tus nqi 5 mV s-1.Vim muaj kev txwv loj, cov ntaub ntawv khaws tseg (Daim duab 4a) feem ntau muaj S-zoo li txuas mus rau toj siab uas muaj peev xwm tsis zoo.Qhov limiting tam sim no ceev, jL, muaj peev xwm E1/2 (qhov twg j/jL = ½) thiab pib muaj peev xwm ntawm -0.1 mA cm-2 tau muab rho tawm los ntawm cov phiaj no thiab teev nyob rau hauv Table 2. Nws yog tsim nyog sau cia tias nyob rau hauv daim duab.4a, catalysts tuaj yeem raug cais raws li lawv qhov E1/2 muaj peev xwm rau hauv: (I) hlau oxides, (II) cov ntaub ntawv carbonaceous, thiab (III) noble hlau.
Linear sweep voltammograms ntawm (a) catalyst thiab (b) nyias zaj duab xis ntawm catalyst thiab XC-72R, ntsuas ntawm RDE glassy carbon sojntsuam ntawm 400 rpm nrog tus nqi scan ntawm 5 mV s-1 hauv O2 saturation ntawm 298 K hauv 1 M NaOH cf.
Tus kheej hlau oxides ntawm Mn thiab Co nyob rau hauv pab pawg I qhia thawj qhov muaj peev xwm ntawm -0.17 V thiab -0.19 V feem, thiab E1/2 qhov tseem ceeb yog nyob nruab nrab ntawm -0.24 thiab -0.26 V. Qhov txo qis ntawm cov hlau oxides no tau nthuav tawm hauv kev sib npaug .(1) thiab (2), uas tshwm sim ib sab ntawm qhov pib muaj peev xwm hauv Fig.4a phim tus qauv peev xwm ntawm thawj kauj ruam 2e ntawm ORR txoj hauv kev ncaj nraim hauv kab zauv.(3).
Cov hlau oxides sib xyaw MnCo2O4 thiab NiCo2O4 hauv tib pab pawg qhia me ntsis kho qhov pib muaj peev xwm ntawm -0.10 thiab -0.12 V raws, tab sis khaws E1/2 qhov tseem ceeb ntawm 10.-0.23 volts.
Pawg II carbon cov ntaub ntawv qhia ntau qhov zoo E1/2 qhov tseem ceeb tshaj li pab pawg I hlau oxides.Cov khoom siv Graphene muaj qhov pib muaj peev xwm ntawm -0.07 V thiab E1 / 2 tus nqi ntawm -0.11 V, thaum lub peev xwm pib thiab E1/2 ntawm 72R Vulcan XC- yog -0.12V thiab -0.17V raws li.Hauv pab pawg III, 5 wt% Pt / C pom qhov zoo tshaj plaws pib muaj peev xwm ntawm 0.02 V, E1 / 2 ntawm -0.055 V, thiab qhov siab tshaj plaws ntawm -0.4 V, txij li kev txo cov pa oxygen tshwm sim los ntawm qhov ceev tam sim no ntawm 4e txoj kev. .Nws kuj tseem muaj qhov qis tshaj E1/2 vim qhov siab conductivity ntawm Pt / C thiab thim rov qab kinetics ntawm ORR cov tshuaj tiv thaiv.
Daim duab S2a nthuav qhia Tafel nqes hav tsom rau ntau yam catalysts.Kinetically tswj cheeb tsam ntawm 5 wt.% Pt / C pib ntawm 0.02 V nrog rau Hg / HgO, thaum lub cheeb tsam ntawm cov hlau oxides thiab carbon cov ntaub ntawv nyob rau hauv ntau yam tsis zoo muaj peev xwm ntawm -0.03 rau -0.1 V. Qhov nqes hav tus nqi rau Tafel Pt / C yog -63.5 mV ss-1, uas yog ib qho tseem ceeb rau Pt ntawm qhov tam sim no ntom ntom dE / d log i = -2.3 RT / F31.32 nyob rau hauv uas tus nqi-txhais kauj ruam cuam tshuam nrog kev hloov pauv ntawm oxygen los ntawm physisorption mus rau Chemisorption 33, 34.Tafel nqes hav qhov tseem ceeb rau cov ntaub ntawv carbon yog nyob rau hauv tib cheeb tsam li Pt/C (-60 mus rau -70 mV div-1), qhia tias cov ntaub ntawv no muaj xws li ORR txoj kev.Tus kheej cov hlau oxides ntawm Co thiab Mn qhia Tafel slopes xws li -110 mus rau -120 mV dec-1, uas yog dE / d log i = -2.3 2RT / F, qhov twg tus nqi-txhais kauj ruam yog thawj electron.Hloov cov kauj ruam 35, 36. me ntsis siab dua nqes hav qhov tseem ceeb sau tseg rau cov hlau oxides sib xyaw NiCo2O4 thiab MnCo2O4, txog -170 mV dec-1, qhia tias muaj OH- thiab H2O ions nyob rau saum npoo ntawm oxide, uas tiv thaiv cov pa oxygen adsorption thiab hloov hluav taws xob, yog li cuam tshuam rau oxygen.txo txoj kev 35.
Qhov sib npaug ntawm Kutetsky-Levich (KL) tau siv los txiav txim siab cov tshuaj tiv thaiv kinetic rau ntau cov qauv catalyst yam tsis muaj kev hloov pauv loj.hauv kev sib npaug.(4) tag nrho cov ntsuas tam sim no ceev j yog qhov sib npaug ntawm qhov tam sim no qhov ntom ntom ntawm electron hloov thiab hloov loj.
los ntawm kev sib npaug.(5) Lub limiting tam sim no ceev jL yog proportional rau lub square cag ntawm kev sib hloov ceev.Yog li ntawd, qhov sib npaug ntawm KL.(6) piav qhia txog kab kab ntawm j−1 piv rau ω−1//2, qhov twg qhov kev sib tshuam yog jk thiab txoj kab nqes ntawm daim duab yog K.
qhov twg ν yog kinematic viscosity ntawm cov electrolyte 1 M NaOH (1.1 × 10–2 cm2 s–1)37, D yog diffusion coefficient ntawm O2 hauv 1 M NaOH (1.89 × 10–5 cm2 s–1) 38, ω yog rpm yog qhov kev sib hloov ceev, C yog cov pa oxygen concentration hauv cov kua ntau (8.4 × 10–7 mol cm–3) 38.
Sau linearly swept voltammograms siv RDE ntawm 100, 400, 900, 1600, thiab 2500 rpm.Cov txiaj ntsig tau raug coj los ntawm -0.4 V hauv thaj tsam txwv loj hloov mus rau lub phiaj xwm KL daim duab, piv txwv li -j-1 piv rau ω-1//2 rau cov catalyst (Fig. S3a).Siv qhov sib npaug.Hauv kev sib npaug (6) thiab (7), cov ntsuas kev ua tau zoo ntawm cov catalyst, xws li cov kinetic tam sim no ceev yam tsis xav txog qhov cuam tshuam ntawm huab hwm coj hloov jk, txiav txim siab los ntawm qhov taw tes ntawm kev sib tshuam nrog y axis, thiab tus naj npawb ntawm Kev hloov hluav taws xob yog txiav txim siab los ntawm gradient K ntawm qhov nkhaus.Lawv tau teev nyob rau hauv rooj 2.
5 wt% Pt/C thiab XC-72R muaj qhov qis tshaj plaws ntawm jk qhov tseem ceeb, qhia txog kev hloov pauv sai rau cov ntaub ntawv no.Txawm li cas los xij, txoj kab nqes ntawm XC-72R nkhaus yog yuav luag ob zaug uas rau 5 wt% Pt / C, uas xav tau txij li K yog qhov qhia txog tus naj npawb ntawm cov hluav taws xob hloov thaum lub sij hawm txo cov pa oxygen.Raws li kev xav, KL zaj duab xis rau 5 wt% Pt / C yuav tsum dhau los ntawm 39 keeb kwm raws li kev hloov pauv loj, txawm li cas los xij qhov no tsis tau pom hauv daim duab S3a, qhia txog kev txwv kinetic lossis diffusional cuam tshuam rau cov txiaj ntsig.Qhov no tej zaum yuav yog vim Garsani et al.40 tau pom tias qhov tsis sib xws me me hauv topology thiab morphology ntawm Pt/C catalytic films tuaj yeem cuam tshuam qhov tseeb ntawm ORR qhov tseem ceeb.Txawm li cas los xij, txij li tag nrho cov yeeb yaj kiab catalyst tau npaj rau tib txoj kev, ib qho kev cuam tshuam ntawm cov txiaj ntsig yuav tsum zoo ib yam rau tag nrho cov qauv.Lub graphene KL cross point ntawm ≈ -0.13 mA-1 cm2 yog piv rau XC-72R, tab sis qhov -0.20 mA-1 cm2 cross point rau N-doped graphene KL daim duab qhia tias tam sim no qhov ntom ntom ntau dua nyob ntawm qhov voltage ntawm lub catalytic converter.Qhov no tej zaum yuav yog vim qhov tseeb tias nitrogen doping ntawm graphene txo cov hluav taws xob tag nrho, ua rau qeeb hluav taws xob hloov kinetics.Hauv qhov sib piv, qhov tseeb K tus nqi ntawm nitrogen-doped graphene yog me dua li ntawm graphene vim tias muaj nitrogen pab tsim ntau qhov chaw rau ORR41,42.
Rau oxides raws li manganese, qhov kev sib tshuam ntawm qhov loj tshaj plaws tus nqi yog pom - 0.57 mA-1 cm2.Txawm li cas los xij, qhov tseeb K tus nqi ntawm MnOx yog qis dua li ntawm MnO2 thiab ze li 5 wt %.% Pt/C.Cov lej hloov hluav taws xob tau txiav txim siab yog kwv yees.MnOx yog 4 thiab MnO2 yog ze rau 2. Qhov no yog raws li cov txiaj ntsig tau luam tawm hauv cov ntaub ntawv, uas tau tshaj tawm tias cov xov tooj ntawm cov hluav taws xob hloov mus rau hauv txoj kev α-MnO2 ORR yog 4, thaum β-MnO243 feem ntau tsawg dua 4. Yog li. , ORR txoj hauv kev sib txawv rau ntau hom polymorphic catalysts raws li manganese oxide, txawm hais tias tus nqi ntawm cov kauj ruam tshuaj tseem nyob li qub.Tshwj xeeb, MnOx thiab MnCo2O4 catalysts muaj cov lej hloov hluav taws xob me ntsis siab dua 4 vim tias qhov txo qis ntawm manganese oxides tam sim no hauv cov catalysts tshwm sim ib txhij nrog txo cov pa oxygen.Hauv kev ua haujlwm dhau los, peb pom tias electrochemical txo ntawm manganese oxide tshwm sim nyob rau hauv tib lub peev xwm ntau npaum li qhov txo cov pa oxygen hauv cov tshuaj saturated nrog nitrogen28.Kev koom tes ntawm cov kev tawm tsam sab nraud ua rau suav tus lej ntawm cov hluav taws xob me ntsis ntau dua 4.
Qhov kev sib tshuam ntawm Co3O4 yog ≈ −0.48 mA-1 cm2, uas yog qhov tsis zoo tsawg dua ob hom manganese oxide, thiab pom meej electron hloov tus lej yog txiav txim siab los ntawm tus nqi ntawm K sib npaug 2. Hloov Ni hauv NiCo2O4 thiab Mn hauv MnCo2O4. los ntawm Co ua rau qhov txo qis hauv qhov tseem ceeb K, uas qhia txog kev txhim kho hauv cov hluav taws xob hloov hluav taws xob hauv cov hlau oxides sib xyaw.
Cov pa roj carbon substrates tau ntxiv rau ORR catalyst ink kom nce hluav taws xob conductivity thiab pab kom tsim nyog peb-theem ciam teb hauv cov roj diffusion electrodes.Vulcan-XC-72R raug xaiv vim nws tus nqi qis, thaj tsam loj ntawm 250 m2·g-1, thiab tsis tshua muaj zog ntawm 0.08 txog 1 Ω·cm44.45.Ib qho LSV zaj duab xis ntawm cov qauv catalyst tov nrog Vulcan XC-72R ntawm 400 rpm yog qhia hauv daim duab 1. 4b.Cov txiaj ntsig pom tseeb tshaj plaws ntawm kev ntxiv Vulcan XC-72R yog txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhuam nwsNco ntsoov tias qhov no tseem ceeb dua rau cov hlau oxides, nrog rau qhov ntxiv 0.60 mA cm-2 rau ib leeg hlau oxides, 0.40 mA cm-2 rau cov hlau oxides sib xyaw, thiab 0.28 mA cm-2 rau graphene thiab doped graphene.N. Ntxiv 0.05 mA cm-2.-2.Qhov sib ntxiv ntawm Vulcan XC-72R rau lub catalyst number case kuj ua rau muaj kev hloov pauv zoo hauv qhov pib muaj peev xwm thiab E1/2 ib nrab-yoj lub peev xwm rau tag nrho cov catalysts tshwj tsis yog graphene.Cov kev hloov pauv no yuav yog qhov tshwm sim ntawm kev siv hluav taws xob ntau ntxiv ntawm thaj chaw siv 46 thiab txhim kho kev sib cuag47 ntawm cov khoom siv hluav taws xob ntawm kev txhawb nqa Vulcan XC-72R catalyst.
Qhov sib thooj Tafel cov phiaj xwm thiab kinetic tsis rau cov khoom sib xyaw ua ke no tau pom hauv daim duab S2b thiab Table 3, raws li.Tafel nqes hav qhov tseem ceeb yog tib yam rau MnOx thiab graphene cov ntaub ntawv nrog thiab tsis muaj XC-72R, qhia tias lawv txoj kev ORR tsis cuam tshuam.Txawm li cas los xij, cov cobalt-based oxides Co3O4, NiCo2O4 thiab MnCo2O4 muab me me qhov tsis zoo Tafel nqes hav qhov tseem ceeb ntawm -68 thiab -80 mV dec-1 ua ke nrog XC-72R qhia txog kev hloov hauv ORR txoj hauv kev.Daim duab S3b qhia txog KL zaj duab xis rau cov qauv catalyst ua ke nrog Vulcan XC-72R.Feem ntau, qhov txo qis ntawm qhov tseem ceeb ntawm jk tau pom rau tag nrho cov catalysts tov nrog XC-72R.MnOx pom qhov txo qis tshaj plaws ntawm tus nqi ntawm jk los ntawm 55 mA-1 cm2, thaum NiCo2O4 tau sau tseg qhov txo qis los ntawm 32 mA-1 cm-2, thiab graphene pom qhov tsawg tshaj plaws txo los ntawm 5 mA-1 cm2.Nws tuaj yeem txiav txim siab tias qhov cuam tshuam ntawm Vulcan XC-72R ntawm kev ua haujlwm ntawm cov catalyst yog txwv los ntawm kev ua haujlwm ntawm cov catalyst nyob rau hauv cov nqe lus ntawm OVR.
Vulcan XC-72R tsis cuam tshuam rau K qhov tseem ceeb ntawm NiCo2O4, MnCo2O4, graphene, thiab nitrogen-doped graphene.Txawm li cas los xij, tus nqi K ntawm Co3O4 tau txo qis nrog qhov sib ntxiv ntawm Vulcan XC-72R, qhia txog kev nce ntawm cov hluav taws xob hloov pauv los ntawm ORR.Xws li kev koom ua ke ntawm Co3O4 nrog cov khoom siv carbon tau raug tshaj tawm hauv refs.48, 49. Thaum tsis muaj kev txhawb nqa carbon, Co3O4 tau xav tias yuav txhawb nqa qhov tsis sib xws ntawm HO2- rau O2 thiab OH-50.51, uas tau pom zoo nrog Co3O4's electron hloov pauv ntawm li 2 hauv Table 2. Yog li, cov Lub cev adsorption ntawm Co3O4 ntawm cov pa roj carbon substrates yuav tsum tsim kom muaj 2 + 2 plaub-electron ORR pathway52 uas thawj electroreduces O2 rau HO2- ntawm qhov cuam tshuam ntawm Co3O4 catalyst thiab Vulcan XC-72R (kev sib npaug 1) thiab tom qab ntawd HO2 - Qhov sib txawv sai sai. hlau oxide nto yog hloov mus rau O2 ua raws li electroreduction.
Hauv qhov sib piv, qhov tseeb tus nqi ntawm K MnOx tau nce ntxiv nrog qhov sib ntxiv ntawm Vulcan XC-72R, uas sawv cev rau qhov txo qis ntawm cov hluav taws xob hloov hluav taws xob los ntawm 4.6 txog 3.3 (Table 3).Qhov no yog vim muaj ob qhov chaw ntawm carbon catalyst composite rau ob-theem electron txoj kev.Thawj qhov txo qis ntawm O2 rau HO2- tshwm sim yooj yim dua ntawm cov pa roj carbon monoxide, uas ua rau muaj kev nyiam me ntsis ntxiv rau ob txoj hauv kev electron ntawm ORR53.
Kev ruaj ntseg ntawm cov catalyst tau soj ntsuam nyob rau hauv GDE ib nrab-cell nyob rau hauv qhov ntau ntawm tam sim no ntom.Ntawm daim duab.5 qhia cov phiaj xwm muaj peev xwm piv rau lub sijhawm rau GDE MnOx, MnCo2O4, NiCo2O4, graphene, thiab nitrogen-doped graphene.MnOx qhia tag nrho kev ruaj ntseg zoo thiab ORR kev ua tau zoo ntawm qhov tsawg thiab siab tam sim no, qhia tias nws tsim nyog rau kev txhim kho ntxiv.
Chronopotentiometry ntawm HDE cov qauv ntawm tam sim no los ntawm 10 txog 100 mA / cm2 hauv 1 M NaOH, 333 K, O2 txaus tus nqi 200 cm3 / min.
MnCo2O4 kuj zoo nkaus li khaws cia ORR zoo nyob thoob plaws qhov ceev tam sim no, tab sis ntawm qhov tam sim no ntau dua ntawm 50 thiab 100 mA cm-2 loj overvoltages raug pom tias MnCo2O4 tsis ua zoo li MnOx.Graphene GDE nthuav tawm qhov kev ua tau zoo ORR qis tshaj qhov ntsuas qhov ntsuas tam sim no, ua kom pom kev poob qis hauv kev ua haujlwm ntawm 100 mA cm-2.Yog li ntawd, nyob rau hauv qhov kev sim xaiv, MnOx GDE raug xaiv rau kev sim ntxiv hauv Zn-air thib ob system.