Zikomo pochezera Nature.com.Mukugwiritsa ntchito msakatuli wokhala ndi chithandizo chochepa cha CSS.Kuti mumve zambiri, tikupangira kuti mugwiritse ntchito msakatuli wosinthidwa (kapena kuletsa Compatibility Mode mu Internet Explorer).Kuphatikiza apo, kuti tithandizire kupitilizabe, tikuwonetsa tsambalo popanda masitayilo ndi JavaScript.
Masilayidi owonetsa zolemba zitatu pa slide iliyonse.Gwiritsani ntchito mabatani akumbuyo ndi ena kuti mudutse zithunzi, kapena mabatani owongolera masilayidi kumapeto kuti mudutse silayidi iliyonse.
Ma electrocatalyst ogwira mtima, otsika mtengo komanso okhalitsa a oxygen reduction reaction (ORR) ndi ofunika kwambiri pamabatire achiwiri a Zn-air.Ntchito ya ORR ya single and mix metal oxides ndi carbon electrocatalysts idafufuzidwa pogwiritsa ntchito miyeso yozungulira ya disk electrode (RDE), malo otsetsereka a Tafel, ndi ziwembu za Kutetsky-Levich.Zinapezeka kuti kuphatikiza kwa MnOx ndi XC-72R kumawonetsa ntchito yayikulu ya PBP komanso kukhazikika kwabwino, mpaka 100 mA cm-2.Kuchita kwa ma elekitirodi a ORR osankhidwa ndi ma elekitirodi opangidwa kale ndi okosijeni (OER) adayesedwa mu batire yachiwiri ya zinc-mpweya yopangidwa mwachizolowezi mu kachitidwe ka ma elekitirodi atatu, ndi kachulukidwe kamakono, electrolyte molarity, kutentha, kuyera kwa oxygen. anayesedwanso.Makhalidwe a ORR ndi OERma elekitirodi.Potsirizira pake, kukhazikika kwa dongosolo lachiwiri la zinc-air kunayesedwa, kusonyeza mphamvu ya mphamvu ya 58-61% pa 20 mA cm-2 mu 4 M NaOH + 0.3 M ZnO pa 333 K kwa maola 40.
Mabatire achitsulo a mpweya okhala ndi ma elekitirodi okosijeni amawonedwa ngati makina owoneka bwino kwambiri chifukwa zida zamagetsi zama elekitirodi okosijeni zitha kupezedwa mosavuta kuchokera kumlengalenga wozungulira ndipo safuna kusungirako1.Izi zimathandizira kamangidwe kake polola kuti ma elekitirodi a oxygen akhale ndi mphamvu zopanda malire, potero amawonjezera kuchuluka kwa mphamvu zamakina.Chifukwa chake, mabatire achitsulo ampweya omwe amagwiritsa ntchito zinthu za anode monga lithiamu, aluminiyamu, chitsulo, zinki, ndi magnesium atuluka chifukwa cha kuthekera kwawo kwapadera.Pakati pawo, mabatire a mpweya wa zinki amatha kukwaniritsa mtengo, chitetezo, komanso chilengedwe, popeza zinki ili ndi zinthu zambiri zofunika monga zinthu za anode, monga kukhazikika kwa ma electrolyte amadzimadzi, kachulukidwe kakang'ono ka mphamvu, komanso kutsika pang'ono.kuthekera., reversibility electrochemical, conductivity yabwino yamagetsi, kuchuluka komanso kusavuta kugwira4,5.Pakali pano, ngakhale mabatire oyambirira a mpweya wa zinki amagwiritsidwa ntchito pazinthu zamalonda monga zothandizira kumva, zizindikiro za njanji ndi magetsi oyendetsa ndege, mabatire achiwiri a zinc mpweya amatha kukhala ndi mphamvu zowonjezera mphamvu zofanana ndi mabatire a lithiamu.Izi zimapangitsa kukhala koyenera kupitiliza kafukufuku wamabatire a mpweya wa zinki kuti agwiritse ntchito pamagetsi onyamula, magalimoto amagetsi, kusungirako mphamvu zama grid komanso kuthandizira kupanga mphamvu zongowonjezwdwa6,7.
Chimodzi mwazolinga zazikulu ndikupititsa patsogolo kayendetsedwe ka kayendedwe ka mpweya pamagetsi a mpweya, zomwe ndi oxygen reduction reaction (ORR) ndi oxygen evolution reaction (OER), pofuna kulimbikitsa malonda a mabatire achiwiri a Zn-air.Kuti izi zitheke, ma electrocatalysts ogwira ntchito angagwiritsidwe ntchito kuonjezera kuchuluka kwa zomwe zimachitika ndikuwonjezera mphamvu.Pakalipano, ma electrodes a oxygen omwe ali ndi zida zogwiritsira ntchito bifunctional catalysts akufotokozedwa bwino m'mabuku8,9,10.Ngakhale ma catalysts omwe ali ndi bifunctional amatha kuchepetsa mapangidwe a electrode ndikuchepetsa kutayika kwa misa, zomwe zingathandize kuchepetsa ndalama zopangira, pochita, zopangira zomwe zili zoyenera kwa ORR nthawi zambiri sizili zoyenera kwa OER, ndi mosemphanitsa11.Kusiyana kumeneku kwa mphamvu zogwirira ntchito kumapangitsa kuti chothandizira chiwonekere kuzinthu zambiri zomwe zingathe kusintha, zomwe zingasinthe mawonekedwe ake pa nthawi.Kuphatikiza apo, kudalirana kwa mphamvu zomangira zapakatikati kumatanthauza kuti malo omwe amathandizira pachothandizira amatha kukhala osiyana ndi zomwe zimachitika, zomwe zitha kusokoneza kukhathamiritsa.
Vuto lina lalikulu la mabatire achiwiri a Zn-air ndi kapangidwe ka mpweyaelectrode, makamaka chifukwa chothandizira monofunctional cha ORR ndi OER chimagwira ntchito zosiyanasiyana.The ORR mpweya kufalitsa wosanjikiza ayenera kukhala hydrophobic kulola mpweya mpweya kulowa malo othandizira, pamene OER ndi electrode pamwamba ayenera kukhala hydrophilic atsogolere kuchotsa thovu mpweya.Pa mkuyu.1 ikuwonetsa mapangidwe atatu a ma electrode a oxygen omwe adatengedwa kuchokera ku ndemanga ya Jorissen12, yomwe ndi (i) zopangira ma electrode awiri, (ii) zopangira ma electrode awiri kapena angapo, ndi (iii) masanjidwe atatu a electrode.
Kwa mapangidwe oyamba a elekitirodi, omwe amaphatikizanso gawo limodzi lokha lomwe limagwira ntchito limodzi ndi chothandizira chomwe chimayambitsa ORR ndi OER, ngati nembanemba imaphatikizidwa mu kapangidwe kameneka, ndiye kuti msonkhano wa nembanemba-electrode (MEA) umapangidwa monga momwe tawonetsera.Mtundu wachiwiri umaphatikizapo mabedi awiri (kapena kuposerapo) othandizira omwe ali ndi porosity yosiyana ndi hydrophobicity kuti awerengere kusiyana kwa madera13,14,15.Nthawi zina, mabedi awiri othandizira amasiyanitsidwa, mbali ya hydrophilic ya OER ikuyang'anizana ndi electrolyte ndi mbali ya semi-hydrophobic ya ORR ikuyang'anizana ndi malekezero otseguka a electrode 16, 17, 18. selo lopangidwa ndi machitidwe awiri- ma elekitirodi enieni a oxygen ndi electrode ya zinc19,20.Table S1 imatchula zabwino ndi zoyipa za kapangidwe kalikonse.
Kukhazikitsa ma elekitirodi omwe amalekanitsa machitidwe a ORR ndi OER adawonetsa kale kukhazikika kwapang'onopang'ono19.Izi ndizowona makamaka pamakonzedwe atatu a electrode, pomwe kuwonongeka kwa zoyambitsa zosakhazikika ndi zowonjezera zowonjezera kumachepetsedwa ndipo kutulutsa mpweya kumayendetsedwa bwino pamtundu wonse womwe ungathe.Pazifukwa izi, tidagwiritsa ntchito mawonekedwe amagetsi atatu a Zn-air mu ntchitoyi.
M'nkhaniyi, tidasankha zopangira zapamwamba za ORR poyerekeza ma oxide achitsulo osinthika osiyanasiyana, zida za carbonaceous, ndi zopangira zowunikira ndi kuyesa kwa disk electrode (RDE).Transition metal oxides amakonda kukhala ma electrocatalyst abwino chifukwa cha kusiyanasiyana kwawo kwa okosijeni;machitidwe amapangidwa mosavuta pamaso pa mankhwalawa21.Mwachitsanzo, manganese oxides, cobalt oxides, ndi cobalt-based mix oxides (monga NiCo2O4 ndi MnCo2O4)22,23,24 amawonetsa ORR yabwino mumikhalidwe yamchere chifukwa cha d-orbitals yodzaza theka, milingo yamphamvu ya elekitironi yomwe imalola ma elekitironi. ntchito ndikuwongolera kutonthoza mtima.Kuonjezera apo, amakhala ochuluka kwambiri m'chilengedwe ndipo amakhala ndi magetsi ovomerezeka, othamanga kwambiri komanso okhazikika.Mofananamo, zida za carbonaceous zimagwiritsidwa ntchito kwambiri, zomwe zimakhala ndi ubwino wamagetsi apamwamba komanso malo akuluakulu.Nthawi zina, ma heteroatomu monga nayitrogeni, boron, phosphorous, ndi sulfure adalowetsedwa mu kaboni kuti asinthe mawonekedwe ake, kupititsa patsogolo mawonekedwe a ORR azinthu izi.
Kutengera zotsatira zoyeserera, tidaphatikiza zopangira za OVR zosankhidwa mu ma elekitirodi agasi (GDE) ndikuziyesa pamiyeso yosiyanasiyana yapano.Chothandizira kwambiri cha ORR GDE chinasonkhanitsidwa mu batri yathu yamagetsi yamagetsi atatu ya Zn-air pamodzi ndi ma elekitirodi a OER omwe adakonzedwa mu ntchito yathu yapitayi26,27.Kuthekera kwa ma elekitirodi a okosijeni pawokha kunkayang'aniridwa panthawi yomwe amatuluka ndikuyesa kuyesa panjinga kuti aphunzire momwe magwiridwe antchito amagwirira ntchito monga kuchuluka kwa ma electrolyte, kutentha kwa ma cell, komanso kuyera kwa okosijeni.Pomaliza, kukhazikika kwa mabatire achiwiri a Zn-air kudawunikidwa pakuyenda kosalekeza pansi pamikhalidwe yabwino yogwirira ntchito.
MnOx28 idakonzedwa ndi njira ya redox yamankhwala: 50 ml ya 0.04 M KMnO4 yankho (Fisher Scientific, 99%) idawonjezedwa ku 100 ml ya 0.03 Mn (CH3COO)2 (Fisher Scientific, 98%) kuti apange mvula yofiirira.The osakaniza ndi kusintha pH 12 ndi kuchepetsa sodium hydroxide, ndiye centrifuged 3-5 zina pa 2500 rpm kusonkhanitsa mpweya.Kenako madziwo amatsukidwa ndi madzi osakanizidwa mpaka utoto wofiirira wa ion permanganate utatha.Pomaliza, madipozitiwo adawumitsidwa ndi mpweya ku 333 K usiku wonse ndikupunthwa.
Spinel oxides Co3O4, NiCo2O4, ndi MnCo2O4 anapangidwa ndi kuwonongeka kwa matenthedwe.NiCo2O4 ndi MnCo2O4 zinakonzedwa powonjezera 0.5 M (14.5 g) faifi tambala(II) nitrate hexahydrate, Ni(NO3)2⋅6H2O (Fisher Scientific, 99.9%) kapena 0.5 M (12.6 g) tetrahydrate manganese(II) nitrate Mn(NO3) ).) 2 4H2O (Sigma Aldrich, ≥ 97%) ndi 1 M (29.1 g) cobalt (II) nitrate hexahydrate, Co (NO3) 2 6H2O (Fisher Scientific, 98+%, ACS reagents) mu methanol (Fisher Scientific%, 99. ) mu 100 ml ya dilution vial.Methanol amawonjezedwa m'magawo ang'onoang'ono ku kusintha kwazitsulo za nitrate ndikugwedeza mosalekeza mpaka yankho la homogeneous likupezeka.Njira yothetsera vutoli idasamutsidwa ku crucible ndikutenthedwa pa mbale yotentha, ndikusiya mdima wofiira wolimba.Cholimbacho chinawerengedwa pa 648 K kwa maola 20 mumlengalenga.Kenako cholimbacho ankachipera n’kukhala ufa wosalala.No Ni(NO3)2 6H2O kapena Mn(NO3)2 4H2O anawonjezedwa pa synthesis wa Co3O4.
Ma graphene nanosheets okhala ndi malo a 300 m2/g (Sigma Aldrich), graphene doped ndi nitrogen (Sigma Aldrich), carbon black powder (Vulcan XC-72R, Cabot Corp., 100%), MnO2 (Sigma Aldrich) ndi 5 wt.% Pt/C (Acros Organics) idagwiritsidwa ntchito monga momwe zilili.
Miyezo ya RDE (Pine Research Instrumentation) idagwiritsidwa ntchito poyesa ntchito zamitundu yosiyanasiyana ya ORR mu 1 M NaOH.Inki yothandiza yomwe ili ndi 1 mg chothandizira + 1 ml deionized (DI) H2O + 0.5 ml isopropanol (IPA) + 5 µl 5 wt% Nafion 117 (Sigma-Aldrich) idagwiritsidwa ntchito monga momwe zilili.Vulcan XC-72R itawonjezedwa, utoto wothandizawo unali ndi 0.5 mg chothandizira + 0.5 mg Vulcan XC-72R + 1 ml DI HO + 0.5 ml IPA + 5 µl 5 wt% Nafion 117 kuonetsetsa kuti zinthu zikuyenda.The osakaniza anali sonicated kwa mphindi 20 ndi homogenized ntchito Cole-Parmer LabGen 7 Series homogenizer pa 28,000 rpm kwa mphindi 4.Inkiyi idagwiritsidwanso ntchito mu ma aliquots atatu a 8 μl pamwamba pa galasi la carbon elekitirodi (Pine Instrument Company) yokhala ndi mainchesi 4 mm (malo ogwirira ntchito ≈ 0.126 cm2) ndi zouma pakati pa zigawo kuti zipereke katundu wa ≈120 μg cm. -2.Pakati ntchito, galasi mpweya elekitirodi padziko anali motsatizana yonyowa opukutidwa ndi MicroCloth (Buehler) ndi 1.0 mamilimita ndi 0,5 mm alumina ufa (MicroPolish, Buehler) kenako sonication mu deionized H2O.
Zitsanzo za electrode za ORR gasi zidakonzedwa molingana ndi protocol28 yomwe tafotokoza kale.Choyamba, chothandizira ufa ndi Vulcan XC-72R zinasakanizidwa mu chiwerengero cha 1: 1.Ndiye chisakanizo cha njira ya polytetrafluoroethylene (PTFE) (60 wt.% mu H2O) ndi zosungunulira ndi chiŵerengero cha IPA/H2O wa 1: 1 anawonjezera kuti youma ufa osakaniza.Sonicate ndi chothandizira utoto kwa mphindi 20 ndi homogenize kwa mphindi 4 pa 28,000 rpm.Inkiyo inkagwiritsidwa ntchito pang'onopang'ono ndi spatula pa pepala losadulidwa la carbon 13 mm m'mimba mwake (AvCarb GDS 1120) ndikuwumitsa mpaka chothandizira cha 2 mg cm2 chinafikiridwa.
Ma electrode a OER anapangidwa ndi cathodic electrodeposition ya Ni-Fe hydroxide catalysts pa 15 mm x 15 mm chitsulo chosapanga dzimbiri.mauna(DeXmet Corp, 4SS 5-050) monga zanenedwa26,27.Electrodeposition inkachitika mu cell atatu electrode theka-selo (a polymer TACHIMATA galasi galasi pafupifupi 20 cm3) ndi Pt gululi monga pountala elekitirodi ndi Hg/HgO mu 1 M NaOH monga ma elekitirodi.Lolani chothandizira zitsulo zosapanga dzimbiri kuti ziume kuti ziume musanadule malo pafupifupi 0.8 cm2 ndi nkhonya yachitsulo ya 10 mm wandiweyani.
Poyerekeza, ma electrode a ORR ndi OER amalonda adagwiritsidwa ntchito monga kulandiridwa ndikuyesedwa pansi pamikhalidwe yomweyi.Ma elekitirodi amalonda a ORR (QSI Nano Gas Diffusion Electrode, Quantum Sphere, 0.35 mm thick) amakhala ndi manganese ndi carbon oxide wokutidwa ndi faifi tambala wosonkhanitsa panopa, pamene malonda OER elekitirodi (mtundu 1.7, wapadera Magneto anode, BV) ali makulidwe 1.3 mm.mpaka 1.6 mm wokulitsa mauna a titaniyamu wokutidwa ndi Ru-Ir wosakanizidwa wachitsulo okusayidi.
Maonekedwe a pamwamba ndi mawonekedwe a zopangira zidazo zidadziwika pogwiritsa ntchito FEI Quanta 650 FEG scanning electron maikulosikopu (SEM) yomwe imagwira ntchito pansi pa vacuum yayikulu komanso voteji yothamanga ya 5 kV.Ufa X-ray diffraction (XRD) deta anasonkhanitsidwa pa Bruker D8 Advance X-ray diffractometer ndi gwero mkuwa chubu (λ = 1.5418 Å) ndi kusanthula ntchito Bruker Diffraction Suite EVA mapulogalamu.
Miyezo yonse yamagetsi yamagetsi idachitidwa pogwiritsa ntchito pulogalamu ya Biologic SP-150 potentiostat ndi EC-lab.Zitsanzo za RDE ndi GDE zinayesedwa pa njira yokhazikika ya electrode itatu yokhala ndi selo lagalasi la 200 cm3 ndi Laggin capillary monga electrode yowonetsera.Pt mesh ndi Hg/HgO mu 1 M NaOH adagwiritsidwa ntchito ngati ma electrode owerengera ndi mareferensi, motsatana.
Pamiyezo ya RDE pakuyesa kulikonse, electrolyte yatsopano ya 1 M NaOH idagwiritsidwa ntchito, kutentha komwe kumasungidwa kosasintha pa 298 K pogwiritsa ntchito kusamba kwamadzi mozungulira (TC120, Grant).Mpweya wa mpweya (BOC) unali kugwedezeka mu electrolyte kupyolera mu galasi la frit ndi porosity ya 25-50 µm kwa osachepera 30 min musanayambe kuyesa kulikonse.Kuti mupeze ma curve a polarization a ORR, kuthekera kwake kudasinthidwa kuchokera ku 0.1 mpaka -0.5 V (yokhudzana ndi Hg / HgO) pamlingo wa 5 mV s -1 pa 400 rpm.Ma cyclic voltammograms anapezedwa mwa kusesa kuthekera pakati pa 0 ndi -1.0 V ndi Hg/HgO pamlingo wa 50 mV s-1.
Pamiyezo ya HDE, electrolyte ya 1 M NaOH idasungidwa pa 333 K ndi kusamba kwamadzi mozungulira.Malo ogwira ntchito a 0,8 cm2 adawonetsedwa ndi electrolyte ndi mpweya wosalekeza wopita kumbuyo kwa electrode pamlingo wa 200 cm3 / min.Mtunda wokhazikika pakati pa electrode yogwira ntchito ndi electrode yowunikira inali 10 mm, ndipo mtunda wapakati pa electrode yogwira ntchito ndi electrode yowerengera unali 13-15 mm.Waya wa Nickel ndi mauna amapereka kukhudzana kwamagetsi kumbali ya mpweya.Miyezo ya Chronopotentiometric idatengedwa pa 10, 20, 50 ndi 100 mA cm-2 kuti awone kukhazikika ndi mphamvu ya electrode.
Makhalidwe a ma elekitirodi a ORR ndi OER adawunikidwa mu cell yagalasi yokhala ndi jekete ya 200 cm3 yokhala ndi choyika cha PTFE29.Chithunzi chojambula cha dongosololi chikuwonetsedwa mu Chithunzi S1.Ma electrode mu batire amalumikizidwa ndi ma electrode atatu.Elekitirodi yogwira ntchito inali ndi ma elekitirodi osiyana a ORR ndi OER olumikizidwa ndi gawo lopatsirana (Nyimbo, SRD-05VDC-SL-C) ndi chowongolera (Raspberry Pi 2014© model B + V1.2) yokhala ndi anode ya zinki.monga awiri Maelekitirodi ndi ma elekitirodi ofotokoza Hg/HgO mu 4 M NaOH anali pa mtunda wa 3 mm kuchokera anode zinki.Python script yalembedwa kuti igwiritse ntchito ndikuwongolera Raspberry Pi ndi Relay Module.
Selo linasinthidwa kuti likhale ndi anode ya zinki (Goodfellow, 1 mm wandiweyani, 99.95%) ndi chivundikiro cha polima chinalola kuti maelekitirodi ayikidwe pamtunda wokhazikika wa pafupifupi 10 m.4 mm pakati.Nitrile mapulagi mphira anakonza maelekitirodi mu chivindikiro, ndi mawaya faifi tambala (Alfa Aesar, 0.5 mm m'mimba mwake, annealed, 99,5% Ni) ankagwiritsidwa ntchito magetsi kukhudzana maelekitirodi.Zinki zojambulazo anode poyamba kutsukidwa ndi isopropanol ndiyeno ndi madzi deionized, ndi pamwamba zojambulazo anali yokutidwa polypropylene tepi (Avon, AVN9811060K, 25 µm wandiweyani) kuvumbula yogwira dera pafupifupi 0.8 cm2.
Zoyeserera zonse zopalasa njinga zidachitika mu 4 M NaOH + 0.3 M ZnO electrolyte pa 333 K pokhapokha ngati tawonetsa mwanjira ina.Pachithunzichi, Ewe pokhudzana ndi Hg/HgO amatanthauza kuthekera kwa elekitirodi ya okosijeni (ORR ndi OER), Ece potengera Hg/HgO amayimira kuthekera kwa elekitirodi ya zinki, Ecell molingana ndi Hg/HgO imayimira zonse. kuthekera kwa ma cell kapena kusiyana komwe kungatheke.pakati pa mphamvu ziwiri za batri.Oxygen kapena mpweya woponderezedwa unaperekedwa kumbali yakumbuyo ya electrode ya OPP pakuyenda kosalekeza kwa 200 cm3 / min.Kukhazikika kwapang'onopang'ono ndi magwiridwe antchito a maelekitirodi adaphunziridwa pakuchulukira kwamakono kwa 20 mA cm-2, nthawi yozungulira ya 30 min, ndi nthawi yopumula ya OCV ya 1 min pakati pa theka lililonse.Zozungulira 10 zosachepera zidachitidwa pachiyeso chilichonse, ndipo deta idachotsedwa pamizere 1, 5, ndi 10 kuti mudziwe momwe ma electrode alili pakapita nthawi.
The morphology wa chothandizira ORR anali yodziwika ndi SEM (mkuyu. 2), ndi ufa X-ray diffraction miyeso anatsimikizira dongosolo kristalo wa zitsanzo (mkuyu. 3).Mapangidwe a zitsanzo za chothandizira amaperekedwa mu Table 1. 1. Poyerekeza manganese oxides, malonda a MnO2 mumkuyu.2a imakhala ndi tinthu tating'onoting'ono, ndipo mawonekedwe a diffraction mu Chithunzi 3a amagwirizana ndi JCPDS 24-0735 ya tetragonal β-MnO2.100 (541) ya tetrahedally 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, (ndi) 5 wt .% Pt/C.
Mawonekedwe a X-ray a (a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, nitrogen-doped graphene ndi graphene, ndi (g) 5 % platinamu / kaboni.
Pa mkuyu.2c-e, pamwamba morphology wa oxides zochokera cobalt Co3O4, NiCo2O4, ndi MnCo2O4 tichipeza masango a irregularly kakulidwe particles.Pa mkuyu.3c-e akuwonetsa kuti kusintha konsekuzitsuloma oxides ali ndi mawonekedwe a spinel ndi dongosolo lofanana la cubic crystal (JCPDS 01-1152, JCPDS 20-0781, ndi JCPDS 23-1237, motsatira).Izi zikuwonetsa kuti njira yowola yotentha imatha kupanga ma crystalline metal oxides kwambiri, zomwe zikuwonetsedwa ndi nsonga zolimba zodziwika bwino mumayendedwe a diffraction.
Zithunzi za SEM za zida za kaboni zikuwonetsa kusintha kwakukulu.Pa mkuyu.2f Vulcan XC-72R kaboni wakuda imakhala ndi ma nanoparticles odzaza.M'malo mwake, maonekedwe a graphene mu Mkuyu. 2g ndi kwambiri kusokonezeka mbale ndi agglomerations.Komabe, N-doped graphene (mkuyu. 2h) zikuoneka zigwirizana woonda zigawo.Mitundu yofananira ya X-ray ya Vulcan XC-72R, malonda a graphene nanosheets, ndi N-doped graphene mu Mkuyu.3f ikuwonetsa kusintha kwakung'ono mumikhalidwe ya 2θ ya (002) ndi (100) nsonga za kaboni.Vulcan XC-72R imadziwika kuti ndi hexagonal graphite mu JCPDS 41-1487 yokhala ndi nsonga (002) ndi (100) yowonekera pa 24.5 ° ndi 43.2 ° motsatana.Mofananamo, nsonga za (002) ndi (100) za N-doped graphene zimawonekera pa 26.7 ° ndi 43.3 °, motero.Kuzama kwapambuyo komwe kumawonedwa mu X-ray diffraction mapatani a Vulcan XC-72R ndi nitrogen-doped graphene ndi chifukwa cha kusakhazikika kwazinthu izi pamapangidwe awo apamwamba.Mosiyana ndi izi, mawonekedwe a diffraction a graphene nanosheets akuwonetsa nsonga yakuthwa, yozama kwambiri (002) pa 26.5 ° ndi nsonga yaying'ono yotakata (100) pa 44 °, zomwe zikuwonetsa mawonekedwe a crystalline kwambiri a chitsanzo ichi.
Pomaliza, mu mkuyu.Chithunzi cha 2i SEM cha 5 wt.% Pt/C chikuwonetsa zidutswa za carbon zooneka ngati ndodo zokhala ndi zozungulira.Cubic Pt imatsimikiziridwa kuchokera ku nsonga zambiri za 5 wt% Pt / C diffraction pattern mu Fig. 3g, ndipo nsonga ya 23 ° imagwirizana ndi (002) nsonga ya carbon.
Kusesa kwa mzere wa ORR chothandizira voltammogram kunajambulidwa pamlingo wosesa wa 5 mV s-1.Chifukwa cha kuchepa kwa kusamutsa kwakukulu, mamapu osonkhanitsidwa (mkuyu 4a) nthawi zambiri amakhala ndi mawonekedwe a S omwe amafikira kumtunda wokhala ndi kuthekera koyipa kwambiri.Kuchepetsa kachulukidwe kakali pano, jL, kuthekera kwa E1/2 (pomwe j/jL = ½) ndi kuthekera koyambira pa -0.1 mA cm-2 zidachotsedwa pazigawozi ndikulembedwa mu Gulu 2. Ndikoyenera kuzindikira kuti mkuyu.4a, zothandizira zitha kugawidwa molingana ndi kuthekera kwawo kwa E1/2 kukhala: (I) oxides zitsulo, (II) zida za carbonaceous, ndi (III) zitsulo zolemekezeka.
Ma Linear sweep voltammograms a (a) chothandizira ndi (b) filimu yopyapyala ya chothandizira ndi XC-72R, yoyezedwa pa RDE glassy carbon probe pa 400 rpm ndi sikelo ya 5 mV s-1 mu kuchuluka kwa O2 pa 298 K mu 1. M NaOH cf.
Ma oxides achitsulo a Mn ndi Co mu gulu I akuwonetsa kuthekera koyambirira kwa -0.17 V ndi -0.19 V motsatana, ndi E1/2 mfundo zili pakati pa -0.24 ndi -0.26 V. Kuchepa kwa ma oxides zitsulo izi kumawonetsedwa mu equation. .(1) ndi (2), zomwe zimawoneka pafupi ndi kuthekera koyambira mu Mkuyu.4a kufanana ndi kuthekera koyenera kwa gawo loyamba la 2e la njira yosalunjika ya ORR mu equation.(3).
Ma oxides osakanikirana achitsulo MnCo2O4 ndi NiCo2O4 mu gulu lomwelo amawonetsa kuthekera kowongolera pang'ono koyambirira pa -0.10 ndi -0.12 V motsatana, koma amasunga ma E1/2 amtengo pafupifupi 10.−0.23 volts.
Gulu II zida za kaboni zikuwonetsa zabwino kwambiri za E1/2 kuposa ma oxide achitsulo a gulu I.Zinthu za graphene zili ndi kuthekera koyambirira kwa -0.07 V ndi mtengo wa E1/2 wa -0.11 V, pomwe kuthekera koyambirira ndi E1/2 ya 72R Vulcan XC- ndi -0.12V ndi -0.17V motsatana.Mu gulu III, 5 wt% Pt / C inasonyeza kuthekera koyambirira koyambirira pa 0.02 V, E1 / 2 ya -0.055 V, ndi malire apamwamba pa -0.4 V, popeza kuchepetsa mpweya kunachitika kudzera mu kachulukidwe kameneka ka njira ya 4e. .Ilinso ndi E1/2 yotsika kwambiri chifukwa cha kukhazikika kwa Pt/C ndi ma kinetics osinthika a ORR reaction.
Chithunzi cha S2a chikuwonetsa kusanthula kotsetsereka kwa Tafel pazothandizira zosiyanasiyana.Chigawo cholamulidwa ndi kinetically cha 5 wt.% Pt / C chimayamba pa 0.02 V pokhudzana ndi Hg / HgO, pamene dera la zitsulo zazitsulo ndi carbon oxides lili m'gulu lazinthu zoipa kuchokera -0.03 mpaka -0.1 V. Mtengo wotsetsereka kwa Tafel Pt/C ndi -63.5 mV ss–1, zomwe zimafanana ndi Pt pazigawo zotsika kwambiri za density dE/d log i = -2.3 RT/F31.32 momwe gawo lodziwira mlingo limaphatikizapo kusintha kwa mpweya kuchokera ku physisorption kupita ku chemisorption33,34.Makhalidwe otsetsereka a Tafel pazinthu za kaboni ali m'dera lomwelo ndi Pt/C (-60 mpaka -70 mV div-1), kutanthauza kuti zinthuzi zili ndi njira zofananira za ORR.Munthu oxides zitsulo za Co ndi Mn lipoti Tafel otsetsereka kuyambira -110 kuti -120 mV dec-1, amene ndi dE/d chipika i = -2.3 2RT/F, kumene sitepe-kudziwa mlingo ndi elekitironi woyamba.kutengerapo sitepe 35, 36. Pang'ono otsetsereka mfundo zinalembedwa osakaniza zitsulo oxides NiCo2O4 ndi MnCo2O4, pafupifupi -170 mV dec-1, zimasonyeza kukhalapo kwa ma ion OH- ndi H2O pamwamba pa okusayidi, amene kuteteza mpweya adsorption ndi kutengerapo ma elekitironi, potero kumakhudza mpweya.kuchepetsa njira 35.
The Kutetsky-Levich (KL) equation idagwiritsidwa ntchito kudziwa magawo a kinetic reaction pamitundu yosiyanasiyana yothandizira popanda kusamutsa misa.mu equation.(4) chiwerengero chonse choyezedwa pano kachulukidwe j ndi kuchuluka kwa kusamutsidwa kwa ma elekitironi ndi kusamutsa misa.
kuchokera ku equation.(5) Kuchepetsa kachulukidwe kapano jL ndikofanana ndi muzu wapakati wa liwiro lozungulira.Chifukwa chake, KL equation.(6) akufotokoza mzere wa j−1 motsutsana ndi ω−1//2, pamene mphambanoyo ndi jk ndipo malo otsetsereka a graph ndi K.
kumene ν ndi mawonekedwe a kinematic viscosity ya electrolyte 1 M NaOH (1.1 × 10-2 cm2 s-1)37, D ndi gawo la kufalikira kwa O2 mu 1 M NaOH (1.89 × 10-5 cm2 s-1)38, ω ndi rpm ndi liwiro lozungulira, C ndi kuchuluka kwa okosijeni munjira yochulukirapo (8.4 × 10-7 mol cm-3) 38.
Sungani ma voltammogram omwe akusesedwa pamzere pogwiritsa ntchito RDE pa 100, 400, 900, 1600, ndi 2500 rpm.Makhalidwe adatengedwa kuchokera ku -0.4 V m'chigawo chochepa chosinthira misala kuti akonze chithunzi cha KL, mwachitsanzo -j-1 motsutsana ndi ω-1//2 kwa chothandizira (mkuyu S3a).Gwiritsani ntchito ma equation.Mu equation (6) ndi (7), zizindikiro za ntchito za chothandizira, monga kachulukidwe kamakono ka kinetic popanda kuganizira zotsatira za kusamutsidwa kwa jk, zimatsimikiziridwa ndi malo odutsa ndi y axis, ndi chiwerengero cha Kusamutsidwa kwa ma elekitironi kumatsimikiziridwa ndi gradient K pamapindikira.Zalembedwa mu tebulo 2.
5 wt% Pt/C ndi XC-72R ali ndi jk yotsika kwambiri, zomwe zikuwonetsa kuthamanga kwa zida izi.Komabe, kutsetsereka kwa XC-72R curve ndi pafupifupi kuwirikiza kawiri kwa 5 wt% Pt / C, zomwe zimayembekezeredwa popeza K ndi chisonyezero cha chiwerengero cha ma electron omwe amasamutsidwa panthawi ya kuchepetsa mpweya.Mwachidziwitso, chiwembu cha KL cha 5 wt% Pt / C chiyenera kudutsa 39 chiyambi pansi pamikhalidwe yochepa yosamutsira, komabe izi sizikuwoneka mu Chithunzi S3a, kutanthauza kuperewera kwa kinetic kapena kufalikira komwe kumakhudza zotsatira.Izi zitha kukhala chifukwa Garsani et al.40 yasonyeza kuti kusagwirizana kwakung'ono mu topology ndi morphology ya mafilimu ochititsa chidwi a Pt / C angakhudze kulondola kwa ntchito za ORR.Komabe, popeza mafilimu onse othandizira adakonzedwa mofanana, zotsatira zilizonse pazotsatira ziyenera kukhala zofanana ndi zitsanzo zonse.The graphene KL mtanda mfundo ≈ -0.13 mA-1 cm2 n'zofanana ndi XC-72R, koma -0.20 mA-1 cm2 mtanda mfundo ya N-doped graphene KL graph zikusonyeza kuti kachulukidwe panopa kwambiri zimadalira mphamvu yamagetsi pa catalytic converter.Izi zikhoza kukhala chifukwa chakuti nayitrogeni doping wa graphene amachepetsa wonse madutsidwe magetsi, kuchititsa pang'onopang'ono ma elekitironi kusamutsa kinetics.Mosiyana ndi izi, mtengo wokwanira wa K wa graphene wopangidwa ndi nayitrogeni ndi wocheperako kuposa wa graphene chifukwa kukhalapo kwa nayitrogeni kumathandizira kupanga malo ogwirira ntchito a ORR41,42.
Kwa ma oxides otengera manganese, malo ophatikizika amtengo wapatali kwambiri amawonedwa - 0.57 mA-1 cm2.Komabe, mtengo wa K wa MnOx ndi wotsika kwambiri kuposa wa MnO2 ndipo uli pafupi ndi 5 wt %.%Pt/C.Nambala zotumizira ma elekitironi zidatsimikiziridwa kukhala pafupifupi.MnOx ndi 4 ndipo MnO2 ili pafupi ndi 2. Izi zikugwirizana ndi zotsatira zomwe zimafalitsidwa m'mabuku, zomwe zimanena kuti chiwerengero cha electron kusamutsidwa mu njira ya α-MnO2 ORR ndi 4, pamene β-MnO243 nthawi zambiri imakhala yochepa kuposa 4. Choncho Choncho , njira za ORR zimasiyana pamitundu yosiyanasiyana ya polymorphic ya catalysts yochokera ku manganese oxide, ngakhale kuti mitengo ya mankhwala imakhalabe yofanana.Makamaka, zothandizira za MnOx ndi MnCo2O4 zili ndi manambala otengera ma elekitironi apamwamba pang'ono kuposa 4 chifukwa kuchepa kwa manganese oxides omwe amapezeka muzothandizira izi kumachitika nthawi imodzi ndikuchepetsa mpweya.M'ntchito yapitayi, tidapeza kuti kuchepetsedwa kwa electrochemical kwa manganese oxide kumachitika munjira yofananira ndi kuchepetsedwa kwa oxygen mu njira yodzaza ndi nayitrogeni28.Kupereka kwa machitidwe am'mbali kumabweretsa kuchuluka kwa ma elekitironi owerengeka pang'ono kuposa 4.
Mphambano wa Co3O4 ndi ≈ −0.48 mA-1 cm2, yomwe ili yochepa kwambiri kuposa mitundu iwiri ya manganese oxide, ndipo nambala yowonetsera ma electron imatsimikiziridwa ndi mtengo wa K wofanana ndi 2. Kusintha NiCo2O4 ndi Mn mu MnCo2O4 ndi Co kumabweretsa kuchepa kwa mfundo zenizeni K, zomwe zikuwonetsa kusintha kwa ma elekitironi kutengerapo kinetics mu oxides wosanganiza zitsulo.
Magawo a kaboni amawonjezedwa ku inki chothandizira cha ORR kuti awonjezere mphamvu yamagetsi ndikuwongolera mapangidwe oyenera a magawo atatu mumagetsi otulutsa mpweya.Vulcan-XC-72R inasankhidwa chifukwa cha mtengo wake wotsika, malo akuluakulu pamtunda wa 250 m2 · g-1, ndi resistivity yochepa ya 0.08 mpaka 1 Ω · cm44.45.Chiwembu cha LSV cha chitsanzo chothandizira chosakanikirana ndi Vulcan XC-72R pa 400 rpm chikuwonetsedwa mu Chithunzi 1. 4b.Chotsatira chodziwikiratu pakuwonjezera Vulcan XC-72R ndikuwonjezera kachulukidwe komaliza.Dziwani kuti izi zimawonekera kwambiri pazitsulo zazitsulo, zowonjezera 0,60 mA cm-2 pazitsulo zachitsulo chimodzi, 0,40 mA cm-2 pazitsulo zazitsulo zosakanikirana, ndi 0,28 mA cm-2 za graphene ndi doped graphene.N. Onjezani 0.05 mA cm-2.−2.Kuwonjezera kwa Vulcan XC-72R ku inki chothandizira kunapangitsanso kusintha kwabwino mu kuthekera koyambira ndi E1/2 theka la mafunde amphamvu kwa onse othandizira kupatula graphene.Zosinthazi zitha kukhala chifukwa chowonjezeka kagwiritsidwe ntchito ka electrochemical padziko lapansi46 komanso kulumikizidwa bwino47 pakati pa tinthu tating'onoting'ono tothandizira Vulcan XC-72R chothandizira.
Magawo ofananira a Tafel ndi magawo a kinetic pazosakaniza zolimbikitsa izi zikuwonetsedwa mu Chithunzi S2b ndi Gulu 3, motsatana.Makhalidwe otsetsereka a Tafel anali ofanana ndi zida za MnOx ndi graphene zomwe zili ndi XC-72R popanda, kuwonetsa kuti njira zawo za ORR sizinakhudzidwe.Komabe, ma oxides opangidwa ndi cobalt Co3O4, NiCo2O4 ndi MnCo2O4 adapereka madontho ang'onoang'ono otsetsereka a Tafel pakati pa -68 ndi -80 mV dec-1 kuphatikiza XC-72R kuwonetsa kusintha kwa njira ya ORR.Chithunzi S3b chikuwonetsa chiwembu cha KL cha chitsanzo chothandizira chophatikizidwa ndi Vulcan XC-72R.Nthawi zambiri, kuchepa kwa mfundo zenizeni za jk kunawonedwa pazothandizira zonse zosakanikirana ndi XC-72R.MnOx inasonyeza kuchepa kwakukulu kwa mtengo wa jk ndi 55 mA-1 cm2, pamene NiCo2O4 inalemba kuchepa kwa 32 mA-1 cm-2, ndipo graphene inasonyeza kuchepa kochepa kwambiri ndi 5 mA-1 cm2.Zitha kuganiziridwa kuti zotsatira za Vulcan XC-72R pakuchita kwa chothandizira ndizochepa ndi ntchito yoyamba ya chothandizira malinga ndi OVR.
Vulcan XC-72R sichikhudza ma K a NiCo2O4, MnCo2O4, graphene, ndi nitrogen-doped graphene.Komabe, mtengo wa K wa Co3O4 unachepa kwambiri ndi kuwonjezera kwa Vulcan XC-72R, kusonyeza kuwonjezeka kwa ma electron omwe amasamutsidwa ndi ORR.Kuyanjana kotereku kwa Co3O4 ndi zigawo za kaboni kwanenedwa m'mawu.48, 49. Popanda chithandizo cha carbon, Co3O4 imaganiziridwa kuti imalimbikitsa kusagwirizana kwa HO2- kwa O2 ndi OH-50.51, zomwe zimagwirizana bwino ndi chiwerengero cha Co3O4's electron kutumiza pafupifupi 2 mu Table 2. Choncho, kutengeka kwa thupi kwa Co3O4 pamagawo a kaboni akuyembekezeka kupanga njira ya 2 + 2 ya ma elekitironi anayi ORR52 yomwe imayambira ma elekitirodi O2 kupita ku HO2- pamawonekedwe a chothandizira cha Co3O4 ndi Vulcan XC-72R (equation 1) kenako HO2 - The mwachangu disproportioned zitsulo okusayidi pamwamba amasandulika O2 kenako electroreduction.
Mosiyana ndi zimenezi, mtengo wathunthu wa K MnOx unawonjezeka ndi kuwonjezera kwa Vulcan XC-72R, zomwe zimayimira kuchepa kwa chiwerengero cha ma electron kuchokera ku 4.6 mpaka 3.3 (Table 3).Izi ndi chifukwa cha kukhalapo kwa malo awiri pa carbon catalyst composite pa njira ziwiri za electron.Kuchepetsa koyambirira kwa O2 kupita ku HO2- kumachitika mosavuta pazithandizo za kaboni, zomwe zimapangitsa kuti kuchuluke pang'ono kwa njira ya ma elekitironi awiri a ORR53.
Kukhazikika kwa chothandizira kudawunikidwa mu GDE theka-selo mumitundu yosiyanasiyana yamasiku ano.Pa mkuyu.5 ikuwonetsa ziwembu zomwe zingatheke motsutsana ndi nthawi ya GDE MnOx, MnCo2O4, NiCo2O4, graphene, ndi nitrogen-doped graphene.MnOx ikuwonetsa kukhazikika kwabwino komanso magwiridwe antchito a ORR pamakachulukidwe otsika komanso apamwamba, kutanthauza kuti ndiyoyenera kukhathamiritsanso.
Chronopotentiometry ya HDE zitsanzo pakali pano kuchokera 10 mpaka 100 mA / cm2 mu 1 M NaOH, 333 K, O2 kuthamanga kwa 200 cm3 / min.
MnCo2O4 imaonekanso kukhalabe okhazikika bwino ORR kudutsa panopa kachulukidwe osiyanasiyana, koma apamwamba kachulukidwe panopa 50 ndi 100 mA cm-2 overvoltages lalikulu anaona kusonyeza kuti MnCo2O4 si bwino ngati MnOx.Graphene GDE ikuwonetsa magwiridwe antchito otsika kwambiri a ORR kuposa kuchuluka kwa kachulukidwe komwe kamayesedwa, kuwonetsa kutsika kofulumira pa 100 mA cm-2.Chifukwa chake, pansi pamikhalidwe yoyeserera yosankhidwa, MnOx GDE idasankhidwa kuti iyesedwenso mu dongosolo lachiwiri la Zn-air.