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Ingantattun, rahusa da ɗorewa na rage iskar oxygen (ORR) na'urorin lantarki suna da matuƙar mahimmanci ga batirin Zn-air na biyu.An bincika ayyukan ORR na ƙarfe guda ɗaya da gauraye na oxides da carbon electrocatalysts ta amfani da ma'aunin faifai mai juyawa (RDE), gangaren Tafel, da makircin Kutetsky-Levich.An gano cewa haɗin MnOx da XC-72R yana nuna babban aikin PBP da kwanciyar hankali mai kyau, har zuwa 100 mA cm-2.An gwada aikin na'urorin lantarki da aka zaɓa na ORR da kuma ingantaccen ingantaccen yanayin juyin halittar oxygen (OER) a baya a cikin baturin zinc-iska da aka gina ta al'ada a cikin tsarin lantarki guda uku, da yawa na yanzu, molarity electrolyte, zafin jiki, tsabtar oxygen sun kasance. kuma an gwada.Halayen ORR da OERlantarki.A ƙarshe, an ƙididdige ƙarfin tsarin zinc-air na biyu, yana nuna ingantaccen makamashi na 58-61% a 20 mA cm-2 a cikin 4 M NaOH + 0.3 M ZnO a 333 K don 40 hours.
Ana ɗaukar batir ɗin ƙarfe-iska tare da na'urorin lantarki na oxygen suna ɗaukar tsarin da ke da kyau sosai saboda ana iya samun kayan lantarki na lantarki na iskar oxygen cikin sauƙi daga yanayin da ke kewaye kuma baya buƙatar ajiya1.Wannan yana sauƙaƙa ƙirar tsarin ta hanyar ƙyale wutar lantarki ta iskar oxygen ta sami ƙarfi mara iyaka, ta haka ƙara ƙarfin ƙarfin tsarin.Saboda haka, batura-iska da ke amfani da kayan anode irin su lithium, aluminum, iron, zinc, da magnesium sun fito ne saboda kyakkyawan ƙarfinsu na musamman.Daga cikin su, batura na iska na zinc suna da ikon saduwa da buƙatun kasuwa don farashi, aminci, da abokantaka na muhalli, tunda zinc yana da halaye masu kyau da yawa kamar kayan anode, kamar ingantaccen kwanciyar hankali a cikin masu amfani da ruwa mai ƙarfi, ƙarancin kuzari, da ƙarancin daidaito.m., electrochemical reversibility, mai kyau lantarki watsin, yalwa da sauƙi na handling4,5.A halin yanzu, ko da yake ana amfani da baturan iska na farko na zinc a aikace-aikacen kasuwanci kamar na'urorin sauraron ji, siginar jirgin ƙasa da fitilun kewayawa, batirin iska na zinc na biyu suna da yuwuwar ƙarfin ƙarfin ƙarfin kwatankwacin baturan tushen lithium.Wannan ya sa ya dace don ci gaba da bincike kan baturan iska na zinc don aikace-aikace a cikin na'urorin lantarki masu ɗaukuwa, motocin lantarki, ma'aunin makamashi na grid da kuma tallafawa samar da makamashi mai sabuntawa6,7.
Ɗaya daga cikin maƙasudin maƙasudin shine haɓaka haɓakar halayen iskar oxygen a iskar lantarki, wato rage yawan iskar oxygen (ORR) da kuma yanayin juyin halittar iskar oxygen (OER), don haɓaka kasuwancin batirin Zn-air na biyu.Don wannan karshen, za a iya amfani da ingantattun na'urorin lantarki don ƙara yawan amsawa kuma don haka ƙara yawan aiki.A halin yanzu, oxygen electrodes tare da bifunctional catalysts an bayyana su da kyau a cikin wallafe-wallafen8,9,10.Ko da yake bifunctional catalysts na iya sauƙaƙa tsarin na'urorin lantarki da kuma rage yawan asarar canja wuri, wanda zai iya taimakawa wajen rage farashin samarwa, a aikace, masu haɓakawa waɗanda suka fi dacewa da ORR sau da yawa ba su dace da OER ba, kuma akasin haka11.Wannan bambance-bambance a cikin yuwuwar aiki yana sa mai haɓakawa ya fallasa zuwa ga fa'ida mai fa'ida, wanda zai iya canza tsarin sa na tsawon lokaci.Bugu da ƙari, haɗin kai na matsakaicin ƙarfin ɗauri yana nufin cewa shafuka masu aiki akan mai kara kuzari na iya bambanta ga kowane amsa, wanda zai iya rikitar da haɓakawa.
Wata babbar matsala ga batirin Zn-air na biyu shine ƙirar iskar oxygenlantarki, galibi saboda masu haɓakawa guda ɗaya na ORR da OER suna aiki a cikin kafofin watsa labarai daban-daban.Dole ne Layer watsa iskar Gas na ORR ya zama hydrophobic don ba da damar iskar oxygen shiga cikin wuraren da ke haifar da kuzari, yayin da ga OER farfajiyar lantarki dole ne ta zama hydrophilic don sauƙaƙe cire kumfa oxygen.A kan fig.1 yana nuna nau'ikan nau'ikan na'urorin lantarki na oxygen guda uku waɗanda aka ɗauka daga bita ta Jorissen12, wato (i) masu haɓakawa na monolayer bifunctional, (ii) masu haɓakawa biyu ko multilayer, da (iii) daidaitawar lantarki guda uku.
Don ƙirar na'urar lantarki ta farko, wacce ta ƙunshi nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau’in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau’in nau’in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau'in nau‘in kifayen da ya zayyana abin da ya hada da mai kara kuzari guda daya) yana haifar da ORR da OER, idan an hada da membrane a cikin wannan zane, to ana samar da taron membrane-electrode (MEA) kamar yadda aka nuna.Nau'in na biyu ya haɗa da gadaje masu haɓakawa guda biyu (ko fiye) tare da porosity daban-daban da hydrophobicity don lissafin bambance-bambance a yankuna masu amsawa13,14,15.A wasu lokuta, biyu catalytic gadaje sun rabu, tare da hydrophilic gefen OER yana fuskantar electrolyte da kuma Semi-hydrophobic gefen ORR fuskantar bude iyakar da electrodes 16, 17, 18. wani cell kunshi biyu dauki- ƙayyadaddun lantarki na oxygen da lantarki na zinc19,20.Tebura S1 ya lissafa fa'idodi da rashin amfanin kowane ƙira.
Aiwatar da ƙirar na'urar lantarki wanda ke raba halayen ORR da OER ya nuna a baya ya nuna ingantaccen kwanciyar hankali na keke19.Wannan gaskiya ne musamman ga ƙayyadaddun na'urorin lantarki guda uku, inda aka rage raguwar ɓarna na masu kara kuzari da abubuwan haɗin gwiwa kuma fitar da iskar gas ta fi ƙarfin iya sarrafawa gaba ɗaya.Don waɗannan dalilai, mun yi amfani da tsarin Zn-air na lantarki uku a cikin wannan aikin.
A cikin wannan labarin, mun fara zaɓar manyan abubuwan haɓakawa na ORR ta hanyar kwatanta nau'ikan oxides na ƙarfe na tsaka-tsaki, kayan carbonaceous, da abubuwan haɓakawa tare da gwaje-gwajen faifan diski mai juyawa (RDE).Canjin karfe oxides ayan zama mai kyau electrocatalysts saboda daban-daban hadawan abu da iskar shaka jihohin;halayen sun fi sauƙi catalyzed a gaban waɗannan mahadi21.Misali, manganese oxides, cobalt oxides, da cobalt-based gauraye oxides (kamar NiCo2O4 da MnCo2O4)22,23,24 suna nuna ORR mai kyau a cikin yanayin alkaline saboda cikar d-orbitals na rabin-cika, matakan makamashin lantarki waɗanda ke ba da izinin lantarki. aiki da ingantaccen yanke ta'aziyya.Bugu da ƙari, sun fi yawa a cikin yanayi kuma suna da karfin wutar lantarki mai karɓa, babban aiki da kwanciyar hankali.Hakazalika, ana amfani da kayan carbonaceous ko'ina, suna da fa'idodin haɓakar wutar lantarki da babban yanki.A wasu lokuta, an shigar da heteroatoms kamar nitrogen, boron, phosphorus, da sulfur a cikin carbon don gyara tsarinsa, ƙara haɓaka halayen ORR na waɗannan kayan.
Dangane da sakamakon gwaji, mun haɗa da zaɓaɓɓun abubuwan haɓakawa na OVR a cikin na'urori masu rarraba iskar gas (GDE) kuma mun gwada su a yawancin abubuwan da ke yanzu.Mafi inganci ORR GDE mai haɓakawa sannan aka haɗa shi a cikin al'adarmu ta al'ada uku-electrode sakandare Zn-air baturi tare da takamaiman amsawa na OER da aka inganta a cikin aikinmu na baya26,27.Abubuwan da ake iya amfani da na'urorin lantarki guda ɗaya na oxygen an sa ido a yayin ci gaba da fitarwa da cajin gwaje-gwajen keke don nazarin tasirin yanayin aiki kamar yawa na yanzu, molarity electrolyte, zafin aikin salula, da tsabtar oxygen.A ƙarshe, an kimanta kwanciyar hankalin batir na biyu na Zn-air a ƙarƙashin ci gaba da hawan keke a ƙarƙashin ingantattun yanayin aiki.
An shirya MnOx28 ta hanyar hanyar redox na sinadarai: 50 ml na maganin 0.04 M KMnO4 (Fisher Scientific, 99%) an ƙara zuwa 100 ml na 0.03 M Mn (CH3COO) 2 (Fisher Scientific, 98%) don samar da hazo mai launin ruwan kasa.Ana daidaita cakuda zuwa pH 12 tare da dilute sodium hydroxide, sannan a sanyaya 3-5 sau a 2500 rpm don tattara hazo.Daga nan kuma sai a wanke ruwan da aka zubar da ruwa har sai launin ruwan permanganate ya bace.A ƙarshe, an bushe ajiyar kuɗin iska a 333 K na dare sannan kuma aka tarwatsa.
Spinel oxides Co3O4, NiCo2O4, da MnCo2O4 an haɗa su ta hanyar lalatawar thermal.NiCo2O4 da MnCo2O4 an shirya su ta hanyar ƙara 0.5 M (14.5 g) nickel (II) nitrate hexahydrate, Ni (NO3) 2⋅6H2O (Fisher Scientific, 99.9%) ko 0.5 M (12.6 g) tetrahydrate manganese (II) NO3 nitrate Min ).)2 4H2O (Sigma Aldrich, ≥ 97%) da 1 M (29.1 g) cobalt (II) nitrate hexahydrate, Co (NO3) 2 6H2O (Fisher Scientific, 98+%, ACS reagents) a methanol (Fisher Scientific, 99.9% ) a cikin 100 ml dilution vials.Ana ƙara methanol a cikin ƙananan sassa zuwa nitrate ƙarfe na canzawa tare da ci gaba da motsawa har sai an sami bayani mai kama.Daga nan sai a juye maganin a cikin kwandon shara kuma a yi zafi a kan farantin zafi, a bar wani duhu ja mai duhu.An ƙididdige ƙaƙƙarfan a 648 K don awa 20 a cikin iska.Sakamakon daskararrun da aka samu sai aka niƙa shi zuwa foda mai kyau.Babu Ni(NO3)2 6H2O ko Mn(NO3)2 4H2O da aka ƙara yayin haɗakarwar Co3O4.
Graphene nanosheets tare da wani surface yanki na 300 m2 / g (Sigma Aldrich), graphene doped tare da nitrogen (Sigma Aldrich), carbon baki foda (Vulcan XC-72R, Cabot Corp., 100%), MnO2 (Sigma Aldrich) da kuma 5 wt.% Pt/C (Acros Organics) anyi amfani dashi kamar yadda yake.
An yi amfani da ma'auni na RDE (Instrumentation na Pine) don kimanta ayyukan masu haɓaka ORR daban-daban a cikin 1 M NaOH.An yi amfani da tawada mai ƙara kuzari wanda ya ƙunshi 1 mg mai kara kuzari + 1 ml deionized (DI) H2O + 0.5 ml isopropanol (IPA) + 5 μl 5 wt% Nafion 117 (Sigma-Aldrich) kamar yadda yake.Lokacin da aka ƙara Vulcan XC-72R, fentin catalytic ya ƙunshi 0.5 mg mai kara kuzari + 0.5 MG Vulcan XC-72R + 1 ml DI HO + 0.5 ml IPA + 5 µl 5 wt% Nafion 117 don tabbatar da daidaiton kayan lodi.A cakuda da aka sonicated for 20 minutes da homogenized ta amfani da Cole-Parmer LabGen 7 Series homogenizer a 28,000 rpm for 4 minutes.An yi amfani da tawada a cikin nau'i uku na 8 μl zuwa saman gilashin carbon electrode (Kamfanin Pine Instrument Company) tare da diamita na 4 mm (yankin aiki ≈ 0.126 cm2) kuma ya bushe tsakanin yadudduka don samar da nauyin ≈120 μg cm. -2.Tsakanin aikace-aikace, da gilashin carbon electrode surface aka successively rigar goge da MicroCloth (Buehler) da 1.0 mm da 0.5 mm alumina foda (MicroPolish, Buehler) bi sonication a deionized H2O.
An shirya samfuran lantarki na iskar gas na ORR bisa ga ka'idar mu da aka bayyana a baya28.Na farko, an haɗa foda mai haɓakawa da Vulcan XC-72R a cikin nauyin nauyin 1: 1.Sa'an nan kuma an ƙara cakuda maganin polytetrafluoroethylene (PTFE) (60 wt.% a cikin H2O) da sauran ƙarfi tare da rabo na IPA / H2O na 1: 1 a cikin busassun foda.Sonicate da catalytic fenti na kimanin minti 20 da homogenize na kimanin minti 4 a 28,000 rpm.Daga nan sai aka shafa tawada da ɓacin rai tare da spatula akan takardan carbon da aka riga aka yanke 13 mm a diamita (AvCarb GDS 1120) kuma a bushe har sai an kai ga abun ciki mai ƙara kuzari na 2 mg cm2.
Na'urorin lantarki na OER an ƙirƙira su ta hanyar katodic electrodeposition na Ni-Fe hydroxide masu haɓakawa akan bakin karfe 15mm x 15 mmraga(DeXmet Corp, 4SS 5-050) kamar yadda aka ruwaito 26,27.An yi amfani da wutar lantarki a cikin daidaitaccen rabin tantanin halitta uku-electrode (wani tantanin halitta mai rufi na polymer na kusan 20 cm3) tare da grid Pt azaman na'urar lantarki da Hg/HgO a cikin 1 M NaOH azaman na'urar magana.Bada damar ramin bakin karfe mai kara kuzari ya bushe kafin yanke wani yanki na kusan 0.8 cm2 tare da naushin karfen carbon kauri 10 mm.
Don kwatantawa, an yi amfani da ORR na kasuwanci da na'urorin lantarki na OER kamar yadda aka karɓa kuma aka gwada su ƙarƙashin yanayi iri ɗaya.Lantarki na ORR na kasuwanci (QSI Nano Gas Diffusion Electrode, Quantum Sphere, 0.35 mm lokacin farin ciki) ya ƙunshi manganese da carbon oxide wanda aka lulluɓe tare da mai karɓar ragamar nickel na yanzu, yayin da lantarki na OER na kasuwanci (nau'in 1.7, Magneto anode na musamman, BV) yana da kauri 1.3 mm.har zuwa 1.6 mm faɗaɗa titanium raga mai rufi da Ru-Ir gauraye karfe oxide.
Siffar halittar jiki da abun da ke tattare da masu kara kuzari an siffanta su ta amfani da FEI Quanta 650 FEG scanning microscope (SEM) mai aiki a ƙarƙashin babban injin da kuma ƙara ƙarfin lantarki na 5kV.An tattara bayanan foda X-ray diffraction (XRD) akan Bruker D8 Advance X-ray diffractometer tare da tushen bututun jan karfe (λ = 1.5418 Å) kuma an bincika ta amfani da software na Bruker Diffraction Suite EVA.
An yi duk ma'auni na lantarki ta amfani da Biologic SP-150 potentiostat da software na EC-lab.An gwada samfurori na RDE da GDE akan daidaitaccen saitin lantarki guda uku wanda ya ƙunshi tantanin halitta mai jakin 200 cm3 da Laggin capillary azaman lantarki mai nuni.Pt mesh da Hg/HgO a cikin 1 M NaOH an yi amfani da su azaman na'urorin lantarki da na'urori, bi da bi.
Don ma'aunin RDE a cikin kowane gwaji, an yi amfani da sabon 1 M NaOH electrolyte, wanda zafinsa ya kasance a 298 K ta amfani da ruwan wanka mai yawo (TC120, Grant).Gaseous oxygen (BOC) yana kumfa a cikin electrolyte ta gilashin gilashi tare da porosity na 25-50 µm na akalla 30 min kafin kowane gwaji.Don samun masu lanƙwasa polarization na ORR, an bincika yuwuwar daga 0.1 zuwa -0.5 V (dangane da Hg/HgO) a ƙimar sikanin 5 mV s -1 a 400 rpm.An samo voltammogram na cyclic ta hanyar share yuwuwar tsakanin 0 da -1.0 V da Hg/HgO a ƙimar 50 mV s-1.
Don ma'aunin HDE, 1 M NaOH electrolyte an kiyaye shi a 333 K tare da ruwan wanka mai yawo.An fallasa wani yanki mai aiki na 0.8 cm2 zuwa electrolyte tare da ci gaba da samar da iskar oxygen zuwa gefen baya na lantarki a cikin ƙimar 200 cm3 / min.Tsayayyen nisa tsakanin lantarki mai aiki da na'urar magana shine 10 mm, kuma nisa tsakanin na'urar lantarki da na'urar tambarin ya kasance 13-15 mm.Wayar nickel da raga suna ba da haɗin wutar lantarki a gefen gas.An ɗauki ma'auni na Chronopotentiometric a 10, 20, 50 da 100 mA cm-2 don kimanta daidaito da inganci na lantarki.
An kimanta halayen ORR da na'urorin lantarki na OER a cikin tantanin halitta mai jakin 200 cm3 tare da saka PTFE29.Ana nuna zane-zane na tsarin a cikin Hoto S1.Ana haɗa wayoyin da ke cikin baturin a cikin tsarin lantarki uku.Wutar lantarki mai aiki ta ƙunshi keɓantaccen martani-takamaiman ORR da na'urorin lantarki na OER waɗanda aka haɗa zuwa tsarin relay (Songle, SRD-05VDC-SL-C) da microcontroller (Raspberry Pi 2014© samfurin B+V1.2) tare da anode na zinc.a matsayin nau'i-nau'i Na'urorin lantarki da na'ura mai mahimmanci Hg/HgO a cikin 4 M NaOH sun kasance a nesa na 3 mm daga zinc anode.An rubuta rubutun Python don aiki da sarrafa Rasberi Pi da Module Relay.
An canza tantanin halitta don ɗaukar anode foil na zinc (Goodfellow, kauri 1 mm, 99.95%) kuma murfin polymer ya ba da damar sanya na'urorin lantarki a ƙayyadadden nisa na kusan m 10.4 mm nesa.Nitrile roba matosai ya gyara na'urorin lantarki a cikin murfi, da kuma nickel wayoyi (Alfa Aesar, 0.5 mm diamita, annealed, 99.5% Ni) da aka yi amfani da lantarki lambobin sadarwa na electrodes.An fara tsabtace zinc foil anode tare da isopropanol sannan kuma da ruwa mai narkewa, kuma an rufe fuskar bangon da polypropylene tef (Avon, AVN9811060K, 25 µm lokacin farin ciki) don fallasa wani yanki mai aiki na kusan 0.8 cm2.
Dukkan gwaje-gwajen keke an yi su a cikin 4 M NaOH + 0.3 M ZnO electrolyte a 333 K sai dai in an lura.A cikin adadi, Ewe game da Hg/HgO yana nufin yuwuwar iskar oxygen (ORR da OER), Ece game da Hg/HgO tana wakiltar yuwuwar wutar lantarki ta zinc, Ecell dangane da Hg/HgO tana wakiltar cikakken. yuwuwar tantanin halitta ko bambanci mai yuwuwa.tsakanin karfin baturi biyu.Oxygen ko iskar da aka matse an ba da ita zuwa gefen baya na lantarki na OPP a madaidaicin adadin 200 cm3/min.An yi nazarin kwanciyar hankali na hawan keke da aikin na'urorin lantarki a halin yanzu na 20 mA cm-2, lokacin zagaye na 30 min, da lokacin hutu na OCV na 1 min tsakanin kowane rabin zagaye.An yi mafi ƙarancin zagayowar 10 don kowane gwaji, kuma an fitar da bayanai daga kewayon 1, 5, da 10 don sanin yanayin lantarki a kan lokaci.
Halin ilimin halittar jiki na mai kara kuzari na ORR yana da SEM (Fig. 2), kuma foda X-ray diffraction ma'auni ya tabbatar da tsarin crystal na samfurori (Fig. 3).Ana ba da sigogin tsarin tsarin samfurori masu haɓakawa a cikin Tebur 1. 1. Lokacin kwatanta manganese oxides, MnO2 na kasuwanci a cikin fig.2a ya ƙunshi manyan barbashi, kuma tsarin rarrabawa a cikin siffa 3a ya dace da JCPDS 24-0735 don tetragonal β-MnO2.Akasin haka, a kan MnOx surface a cikin siffa 2b yana nuna ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararrun ƙwararru a cikin siffa 66 ° daidai da kololuwa (110), (220), (310), (211), da kuma (541) na tetrahedrally 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, (da) 5 wt .% Pt/C.
Tsarin X-ray na (a) MnO2, (b) MnOx, (c) Co3O4, (d) NiCo2O4, (e) MnCo2O4, (f) Vulcan XC-72R, graphene-doped nitrogen da graphene, da (g) 5 % platinum / carbon.
A kan fig.2c-e, yanayin yanayin yanayin oxides dangane da cobalt Co3O4, NiCo2O4, da MnCo2O4 sun ƙunshi gungu na ɓangarorin da ba su dace ba.A kan fig.3c-e ya nuna cewa duk waɗannan sauye-sauyekarfeoxides suna da tsarin kashin baya da tsarin kristal irin wannan (JCPDS 01-1152, JCPDS 20-0781, da JCPDS 23-1237, bi da bi).Wannan yana nuna cewa hanyar bazuwar thermal tana da ikon samar da ƙarfe oxides na kristal sosai, kamar yadda tabbataccen ƙaƙƙarfan ƙaƙƙarfan ƙayyadaddun ƙayyadaddun ƙayyadaddun ƙayyadaddun tsari ya nuna.
Hotunan SEM na kayan carbon suna nuna manyan canje-canje.A kan fig.2f Vulcan XC-72R carbon baƙar fata ya ƙunshi nau'ikan nanoparticles masu yawa.Akasin haka, bayyanar graphene a cikin siffa 2g sune faranti masu ɓarna sosai tare da wasu agglomerations.Duk da haka, N-doped graphene (Fig. 2h) ya bayyana ya ƙunshi yadudduka na bakin ciki.Madaidaicin ƙirar X-ray na Vulcan XC-72R, nanosheets na graphene na kasuwanci, da graphene N-doped a cikin Fig.3f yana nuna ƙananan canje-canje a cikin ƙimar 2θ na (002) da (100) kololuwar carbon.Vulcan XC-72R an gano shi azaman graphite hexagonal a cikin JCPDS 41-1487 tare da kololuwa (002) da (100) suna bayyana a 24.5° da 43.2° bi da bi.Hakazalika, kololuwar (002) da (100) na N-doped graphene suna bayyana a 26.7° da 43.3°, bi da bi.Ƙarfin bangon da aka gani a cikin nau'ikan rarrabuwar X-ray na Vulcan XC-72R da graphene-doped nitrogen saboda yanayin rashin daidaituwar yanayin waɗannan kayan a cikin yanayin halittar su.Sabanin haka, tsarin rarrabuwar kawuna na graphene nanosheets yana nuna ƙayyadaddun ƙaƙƙarfan ƙaƙƙarfan kololuwa (002) a 26.5° da ƙaramin ƙarami mai faɗi (100) a 44°, yana nuna yanayin yanayin wannan samfurin.
A ƙarshe, a cikin fig.Hoton 2i SEM na 5 wt.% Pt/C yana nuna guntuwar carbon mai siffar sanda tare da ɓoyayyiyar zagaye.An ƙaddara Cubic Pt daga mafi yawan kololuwa a cikin 5 wt% Pt/C tsarin rarrabawa a cikin Fig. 3g, kuma mafi girma a 23 ° yayi daidai da (002) kololuwar carbon da ake ciki.
An yi rikodin madaidaicin share ORR mai haɓaka voltammogram a ƙimar sharer 5 mV s-1.Saboda iyakoki na canja wurin taro, taswirorin da aka tattara (Fig. 4a) yawanci suna da siffar S da ta miƙe zuwa tudu tare da mafi ƙarancin yuwuwar.Ƙayyadaddun ƙididdiga na yanzu, jL, m E1 / 2 (inda j / jL = ½) da kuma yiwuwar farawa a -0.1 mA cm-2 an cire su daga waɗannan filaye kuma an jera su a cikin Table 2. Ya kamata a lura cewa a cikin fig.4a, ana iya rarraba masu haɓakawa gwargwadon ƙarfinsu na E1/2 cikin: (I) ƙarfe oxides, (II) kayan carbonaceous, da (III) ƙarfe masu daraja.
Voltammograms masu share layin layi na (a) mai haɓakawa da (b) fim na bakin ciki na mai haɓakawa da XC-72R, wanda aka auna akan binciken carbon gilashin RDE a 400 rpm tare da ƙimar sikanin 5 mV s-1 a cikin jikewar O2 a 298 K a cikin 1 M NaOH cf.
Kowane karfe oxides na Mn da Co a cikin rukuni na nuna ikon farko na -0.17 V da -0.19 V bi da bi, da E1 / 2 dabi'u suna tsakanin -0.24 da -0.26 V. An gabatar da ragi na halayen waɗannan ƙarfe oxides a cikin lissafi. .(1) da (2), waɗanda suka bayyana kusa da yuwuwar farawa a cikin Fig.4a dace daidaitaccen yuwuwar matakin farko na 2e na hanyar kai tsaye ta ORR a cikin lissafin.(3).
Haɗaɗɗen ƙarfe oxides MnCo2O4 da NiCo2O4 a cikin rukuni ɗaya suna nuna ɗan gyara ƙarfin farko a -0.10 da -0.12 V bi da bi, amma suna riƙe ƙimar E1/2 kusan 10.-0.23 volts.
Rukunin II kayan carbon suna nuna ingantattun ƙimar E1/2 fiye da rukunin I ƙarfe oxides.Kayan graphene yana da yuwuwar farko na -0.07 V da ƙimar E1/2 na -0.11 V, yayin da yuwuwar farko da E1/2 na 72R Vulcan XC- sune -0.12V da -0.17V bi da bi.A cikin rukuni na III, 5 wt% Pt / C ya nuna mafi kyawun yuwuwar farko a 0.02 V, E1 / 2 na -0.055 V, da matsakaicin iyaka a -0.4 V, tun lokacin da raguwar iskar oxygen ta faru ta hanyar ƙimar halin yanzu na hanyar 4e. .Hakanan yana da mafi ƙanƙanta E1/2 saboda haɓakar haɓakar Pt/C da jujjuyawar motsin motsin ORR.
Hoto S2a yana gabatar da nazarin gangaren Tafel don abubuwa daban-daban.Yankin da ke sarrafa motsi na 5 wt.% Pt / C yana farawa a 0.02 V dangane da Hg / HgO, yayin da yanki na karfe oxides da kayan carbon suna cikin kewayon rashin ƙarfi daga -0.03 zuwa -0.1 V. Ƙimar gangara. don Tafel Pt / C shine -63.5 mV ss-1, wanda shine al'ada ga Pt a ƙananan ƙarancin halin yanzu dE / d log i = -2.3 RT / F31.32 wanda matakin ƙaddarar ƙimar ya ƙunshi sauyawar oxygen daga physisorption zuwa chemissorption33,34.Ƙimar gangaren Tafel don kayan carbon suna cikin yanki ɗaya da Pt / C (-60 zuwa -70 mV div-1), yana ba da shawarar cewa waɗannan kayan suna da hanyoyin ORR iri ɗaya.Kowane karfe oxides na Co da Mn rahoton Tafel gangara jere daga -110 to -120 mV dec-1, wanda shi ne dE/d log i = -2.3 2RT/F, inda matakin-kayyade matakin ne na farko electron.canja wurin mataki 35, 36. Dan kadan mafi girma gangara dabi'u rikodin ga gauraye karfe oxides NiCo2O4 da MnCo2O4, game da -170 mV dec-1, nuna gaban OH- da H2O ions a kan surface na oxide, wanda hana oxygen adsorption da kuma canja wurin electron, ta haka ya shafi oxygen.Hanyar ragewa 35.
An yi amfani da ma'aunin Kutetsky-Levich (KL) don tantance sigogin halayen motsin rai don samfurori masu haɓaka daban-daban ba tare da canja wurin taro ba.a cikin lissafin.(4) jimillar ma'auni na halin yanzu j shine jimillar yawan adadin na yanzu na canja wurin lantarki da kuma canja wurin taro.
daga lissafin.(5) Ƙayyadadden ƙima na yanzu jL yana daidai da tushen murabba'in saurin juyawa.Saboda haka, KL equation.(6) yana bayyana jadawali layi na j-1 da ω−1//2, inda wurin tsaka-tsaki shine jk kuma gangaren jadawali shine K.
inda ν shine dankon kinematic na electrolyte 1 M NaOH (1.1 × 10-2 cm2 s-1) 37, D shine adadin rarrabawar O2 a cikin 1 M NaOH (1.89 × 10-5 cm2 s-1) 38, ω rpm shine saurin juyawa, C shine iskar oxygen a cikin babban bayani (8.4 × 10-7 mol cm-3)38.
Tattara voltammograms da aka share a layi ta amfani da RDE a 100, 400, 900, 1600, da 2500 rpm.An karɓi ƙimar daga -0.4 V a cikin iyakataccen yanki na canja wurin taro don tsara zanen KL, watau -j-1 da ω-1//2 don mai haɓakawa (Fig. S3a).Yi amfani da ma'auni.A cikin ma'auni (6) da (7), alamun aiki na mai haɓakawa, kamar haɓakar motsi na yanzu ba tare da la'akari da tasirin canjin jama'a ba, an ƙaddara ta hanyar tsaka-tsaki tare da axis y, da adadin adadin Ana ƙaddamar da canja wurin lantarki ta hanyar gradient K na lanƙwasa.An jera su a cikin tebur 2.
5 wt% Pt/C da XC-72R suna da mafi ƙarancin ƙimar jk mafi ƙasƙanci, yana nuna saurin motsi ga waɗannan kayan.Duk da haka, gangaren lanƙwan XC-72R kusan sau biyu ne na 5 wt% Pt/C, wanda ake sa ran tun da K alama ce ta adadin electrons da aka canjawa wuri yayin aikin rage iskar oxygen.A ka'ida, makircin KL na 5 wt% Pt / C ya kamata ya wuce ta asalin 39 a ƙarƙashin ƙayyadaddun yanayin canja wurin taro, duk da haka ba a lura da wannan a cikin Hoto S3a ba, yana nuna iyakokin motsi ko yadawa da ke shafar sakamakon.Wannan yana iya zama saboda Garsani et al.40 sun nuna cewa ƙananan rashin daidaituwa a cikin topology da ilimin halittar jiki na fina-finai na Pt / C catalytic na iya rinjayar daidaiton ƙimar ayyukan ORR.Duk da haka, tun da an shirya duk fina-finai masu tayar da hankali a hanya guda, duk wani tasiri akan sakamakon ya kamata ya zama iri ɗaya ga duk samfurori.Ma'anar giciye na graphene KL na ≈ -0.13 mA-1 cm2 yayi daidai da na XC-72R, amma -0.20 mA-1 cm2 giciye ma'aunin giciye na N-doped graphene KL jadawali yana nuna cewa yawancin halin yanzu ya fi girma ya dogara da da ƙarfin lantarki a kan catalytic Converter.Wannan na iya zama saboda gaskiyar cewa nitrogen doping na graphene yana rage yawan ƙarfin lantarki gaba ɗaya, yana haifar da raguwar motsin motsin lantarki.Sabanin haka, madaidaicin ƙimar K na nitrogen-doped graphene ya fi na graphene saboda kasancewar nitrogen yana taimakawa ƙirƙirar ƙarin wuraren aiki don ORR41,42.
Don oxides dangane da manganese, ana lura da madaidaicin madaidaicin mafi girman darajar - 0.57 mA-1 cm2.Duk da haka, cikakkiyar ƙimar K na MnOx ya yi ƙasa da na MnO2 kuma yana kusa da 5 wt %.%Pt/C.An ƙaddara lambobin canja wurin lantarki kusan.MnOx shine 4 kuma MnO2 yana kusa da 2. Wannan ya dace da sakamakon da aka buga a cikin wallafe-wallafen, wanda ya ba da rahoton cewa yawan canja wurin lantarki a cikin hanyar α-MnO2 ORR shine 4, yayin da β-MnO243 yawanci kasa da 4. Don haka , Hanyoyin ORR sun bambanta don nau'o'in polymorphic daban-daban na masu kara kuzari dangane da manganese oxide, kodayake ƙimar matakan sinadarai sun kasance kusan iri ɗaya.Musamman, MnOx da MnCo2O4 masu haɓakawa suna da lambobin canja wurin lantarki dan kadan sama da 4 saboda raguwar manganese oxides da ke cikin waɗannan abubuwan haɓaka yana faruwa a lokaci guda tare da rage iskar oxygen.A cikin aikin da ya gabata, mun gano cewa raguwar electrochemical na manganese oxide yana faruwa ne a cikin kewayon yuwuwar rage yawan iskar oxygen a cikin wani bayani mai cike da nitrogen28.Gudunmawar halayen gefe tana kaiwa zuwa ƙididdige adadin electrons fiye da 4.
Matsakaici na Co3O4 shine ≈ -0.48 mA-1 cm2, wanda ba shi da kyau fiye da nau'i biyu na manganese oxide, kuma lambar canja wurin lantarki ta bayyana an ƙaddara ta darajar K daidai da 2. Sauya Ni a NiCo2O4 da Mn a MnCo2O4 ta Co yana haifar da raguwa a cikin cikakkun dabi'u K, wanda ke nuna haɓakawa a cikin motsin motsi na lantarki a cikin gaurayewar ƙarfe oxides.
Ana ƙara abubuwan da ke haifar da carbon a cikin tawada mai ƙara kuzari na ORR don ƙara ƙarfin wutar lantarki da sauƙaƙe ƙayyadaddun iyaka na matakai uku a cikin na'urorin watsa gas.An zaɓi Vulcan-XC-72R saboda ƙarancin farashinsa, babban yanki na 250 m2 · g-1, da ƙarancin juriya na 0.08 zuwa 1 Ω · cm44.45.An nuna makircin LSV na samfurin mai haɓakawa da aka haɗe da Vulcan XC-72R a 400 rpm a cikin Hoto 1. 4b.Mafi bayyanannen tasirin ƙara Vulcan XC-72R shine ƙara ƙimar ƙimar yanzu.Yi la'akari da cewa wannan ya fi dacewa ga karfe oxides, tare da ƙarin 0.60 mA cm-2 don guda oxides karfe, 0.40 mA cm-2 don gauraye karfe oxides, da 0.28 mA cm-2 na graphene da doped graphene.N. Ƙara 0.05 mA cm-2.-2.Bugu da ƙari na Vulcan XC-72R zuwa tawada mai haɓakawa kuma ya haifar da canji mai kyau a cikin yiwuwar farawa da kuma E1 / 2 rabin raƙuman ruwa ga duk masu haɓakawa banda graphene.Waɗannan canje-canjen na iya kasancewa sakamakon yuwuwar sakamakon ƙara yawan amfani da sararin samaniya na electrochemical46 da ingantacciyar lamba47 tsakanin barbashi mai ƙara kuzari akan mai tallafawa Vulcan XC-72R.
Madaidaicin makircin Tafel da sigogin motsi na waɗannan gaurayawan haɗakarwa ana nuna su a cikin Hoto S2b da Tebu 3, bi da bi.Ƙimar gangaren Tafel sun kasance iri ɗaya ga MnOx da kayan graphene tare da kuma ba tare da XC-72R ba, yana nuna cewa ba a shafi hanyoyin su na ORR ba.Koyaya, oxides na tushen cobalt Co3O4, NiCo2O4 da MnCo2O4 sun ba da ƙananan ƙimar gangaren Tafel tsakanin -68 da -80 mV dec-1 a hade tare da XC-72R yana nuna canji a cikin hanyar ORR.Hoto S3b yana nuna makircin KL don samfurin haɓakawa wanda aka haɗa tare da Vulcan XC-72R.Gabaɗaya, an lura da raguwar cikakkiyar ƙimar jk ga duk masu haɓakawa gauraye da XC-72R.MnOx ya nuna raguwa mafi girma a cikin cikakkiyar ƙimar jk ta 55 mA-1 cm2, yayin da NiCo2O4 ya rubuta raguwa ta 32 mA-1 cm-2, kuma graphene ya nuna raguwa mafi girma ta 5 mA-1 cm2.Ana iya ƙaddamar da cewa tasirin Vulcan XC-72R akan aikin mai haɓakawa yana iyakancewa ta hanyar aikin farko na mai kara kuzari dangane da OVR.
Vulcan XC-72R baya shafar ƙimar K na NiCo2O4, MnCo2O4, graphene, da graphene-doped nitrogen.Koyaya, ƙimar K na Co3O4 ya ragu sosai tare da ƙari na Vulcan XC-72R, yana nuna haɓakar adadin electrons ɗin da ORR ya tura.Irin wannan haɗin gwiwar Co3O4 tare da abubuwan haɗin carbon an ba da rahoton a cikin refs.48, 49. Idan babu tallafin carbon, ana tunanin Co3O4 don inganta rashin daidaituwa na HO2- zuwa O2 da OH-50.51, wanda ke da kyakkyawar yarjejeniya tare da lambar canja wurin wutar lantarki na Co3O4 na game da 2 a cikin Table 2. Saboda haka, Ana sa ran adsorption na jiki na Co3O4 akan abubuwan da ke cikin carbon zai haifar da hanyar 2 + 2-4-electron ORR hanya52 wanda ya fara yin amfani da wutar lantarki ta O2 zuwa HO2- a cikin mahaɗin Co3O4 mai haɓakawa da Vulcan XC-72R (ma'auni 1) sannan HO2 - Rashin daidaituwa cikin sauri. Ƙarfe oxide surface an canza zuwa O2 bi da electroreduction.
Sabanin haka, cikakken ƙimar K MnOx ya karu tare da ƙari na Vulcan XC-72R, wanda ke wakiltar raguwa a lambar canja wurin lantarki daga 4.6 zuwa 3.3 (Table 3).Wannan ya faru ne saboda kasancewar rukunoni biyu a kan abubuwan da ke haifar da haɓakar carbon don hanyar lantarki mai hawa biyu.Ragewar farko na O2 zuwa HO2- yana faruwa da sauƙi akan tallafin carbon, yana haifar da ɗan ƙara fifiko ga hanyar lantarki biyu na ORR53.
An ƙididdige zaman lafiyar mai haɓakawa a cikin GDE rabin cell a cikin kewayon yawa na yanzu.A kan fig.5 yana nuna yuwuwar yuwuwar lokaci don GDE MnOx, MnCo2O4, NiCo2O4, graphene, da graphene-doped nitrogen.MnOx yana nuna kyakkyawan kwanciyar hankali gabaɗaya da aikin ORR a ƙananan ƙarancin ƙima na yanzu, yana nuna cewa ya dace da ƙarin haɓakawa.
Chronopotentiometry na samfuran HDE a halin yanzu daga 10 zuwa 100 mA/cm2 a cikin 1 M NaOH, 333 K, O2 ƙimar kwarara 200 cm3/min.
MnCo2O4 kuma yana da alama yana riƙe da kwanciyar hankali na ORR mai kyau a cikin kewayon yawa na yanzu, amma a mafi girma na yanzu na 50 da 100 mA cm-2 ana lura da babban ƙarfin wuta wanda ke nuna cewa MnCo2O4 ba ya aiki kamar MnOx.Graphene GDE yana nuna mafi ƙanƙanta aikin ORR akan kewayon yawa na yanzu da aka gwada, yana nuna saurin raguwar aiki a 100 mA cm-2.Sabili da haka, a ƙarƙashin yanayin gwaji da aka zaɓa, an zaɓi MnOx GDE don ƙarin gwaje-gwaje a cikin tsarin sakandare na Zn-air.