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Theoretical analysis of tungsten carbide properties as electrocatalyst support for hydrogen electrode reactions

dc.contributor.advisorPašti, Igor
dc.contributor.otherPetković, Milena
dc.contributor.otherMarčeta-Kaninski, Milica
dc.creatorVasić Anićijević, Dragana
dc.date.accessioned2016-07-10T17:16:26Z
dc.date.available2016-07-10T17:16:26Z
dc.date.available2020-07-03T09:35:03Z
dc.date.issued2015-01-16
dc.identifier.urihttps://nardus.mpn.gov.rs/handle/123456789/5746
dc.identifier.urihttp://eteze.bg.ac.rs/application/showtheses?thesesId=3148
dc.identifier.urihttps://fedorabg.bg.ac.rs/fedora/get/o:11467/bdef:Content/download
dc.identifier.urihttp://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=47607567
dc.description.abstractElektrokatalizatori na bazi platine su uobičajeni za katalizu reakcija vodonične elektrode (engl. hydrogen evolution reaction - HER i hydrogen oxidation reaction - HOR) u različitim sistemima za konverziju energije, kao što su elektrolizeri i gorivne ćelije. Zbog visoke cene platine teži se povećanju specifične površine, da bi se poboljšalo iskorišćenje i smanjila ukupna cena katalizatora. Uobičajeni pristup koji se trenutno koristi u PEM sistemima (engl. PEM - polymer electrolite membrane ili proton exchange membrane – elektrolizeri ili gorivne ćelije sa polimernom membranom propusnom za protone kao elektrolitom) podrazumeva dispergovanje Pt-čestica dimenzija 5-10 nm na odgovarajućoj podlozi (ugljenik), ali u ovom slučaju jezgro Ptnanocestice ostaje nedovoljno iskorišćeno. Idealno iskorišćenje platine se postiže distribucijom platine u obliku monosloja (ML) na inertno provodno jezgro, što podrazumeva stvaranje posebne klase nano-strukturnih katalizatora nazvanih ''jezgroomotač'' (engl. core-shell). Na ovaj način postiže se smanjenje potrošnje platine za jedan red veličine. Karbidi prelaznih metala (engl. transition metal carbides – TMC)nalikuju grupi platinskih metala po elektronskim svojstvima i dimenzijama elementarne ćelije, što je podstaklo ispitivanje katalitičke aktivnosti za reakcije vodonične elektrode. Volfram-karbid (WC) pokazuje slične osobine kao i platina u smislu elektronske strukture i hemisorpcije vodonika. Ipak, dobijene gustine struje izmene su manje za 2-3 reda veličine u odnosu na platinske površine, čineći WC atraktivnim samo kao podlogu za katalizator. S druge strane, sinergijski efekat izmedju Pt i WC-podloge u smislu povećanja katalitičke aktivnosti se često spominje u literaturi, međutim, priroda ovog sinergizma nije u potpunosti razjašnjena. Pored platine, ostali metali platinske grupe su atraktivni za ispitivanje kao deo sličnih sistema, koji bi predstavljali neplatinske katalizatore. Ipak, tanki slojevi prelaznih metala do sada nisu sistematski ispitivani u smislu predviđanja i objašnjenja katalitičke aktivnosti i stabilnosti u uslovima reakcija vodonične elektrode kao neophodnog uslova za primenu. U ovom radu su, uz pomoć teorije funkcionala gustine (engl. Density functional theory - DFT) sistematski ispitani tanki slojevi metala (Cu, Ru, Rh, Pd, Ag, Ir, Pt i Au) na WC-podlozi. Posebna pažnja je posvećena monosloju i dvosloju Pt i Pd, uz analizu činilaca interakcije sa WC-podlogom na nivou elektronske strukture. Ispitivanje je prošireno i na monoslojeve drugih prelaznih metala, pri čemu je ukazano na mogućnost predviđanja stabilnosti do sada neispitanih sistema putem veze jačine vezivanja na WCpodlozi i kohezivne energije kao unutrašnjeg svojstva metala. U nastavku je diskutovana mogućnost predviđanja katalitičke aktivnosti površina na osnovu DFT izračunatih veličina, i konstruisana je vulkanska kriva koja povezuje DFT izračunate energije adsorpcije vodonika sa eksperimentalno dobijenim gustinama struje izmene, s obzirom na jednostavan pristup koji se više puta pokazao praktično primenljivim. Poseban osvrt napravljen je na aktivnost Pd i Pt tankih slojeva i na pojam i poreklo sinergije sa WC-podlogom. Od analiziranih monoslojeva najviše pažnje su privukli CuML/WC i RhML/WC, s obzirom na predviđenu aktivnost praktično jednaku Pt(111). Nijedan od ovih sistema nije do sad ispitivan kao katalizator za reakcije vodonične elektrode, a CuML/WC nije eksperimentalno ni pripremljen. Na osnovu teorijske analize, pre svega termodinamičkih, svojstava ovih sistema, ukazano je na mogućnost njihovog dobijanja u uslovima visokog vakuuma, kao i na očekivanu postojanost u uslovima rada vodonične elektrode. Opšti trendovi reaktivnosti na kraju su prodiskutovani i s tačke gledišta vodonik-supstrat interakcije na nivou elektronske strukture i dat je bliži uvid u činioce koji tu interakciju određuju. Dobijeni rezultati ukazali su na mogućnost dobijanja nove klase katalizatora za reakcije vodonične elektrode, zasnovane na pogodnom izboru kombinacije tankog sloja metala i podloge, koji uopšte ne sadrže platinu.sr
dc.description.abstractPlatinum based electrocatalysts are commonly used in catalysis of hydrogen electrode reactions (hydrogen evolution – HER and hydrogen oxidation - HOR) in different energy conversion systems, such as electrolyzers and fuel cells. For the reasons of high cost of platinum, efforts are made to enchance its utilization by broadening its specific surface. A typical state-of-the-art approach in PEM devices is based on dispersion of Pt-nanoparticles (5-10 nm) over appropriate support, such as carbon but in such arrangement Pt nanoparticle core still remains unexploited. Ideal Pt utilization is achieved when it is distributed in a form of monolayer (ML) over an inert conducting core, involving formation of a new class of nanostructured electrocatalysts called coreshell. In comparison to Pt-nanoparticles, Pt consumption is reduced by an order of magnitude. The transition metal carbides (TMC) are similar to Pt-group metals as far as electronic properties, as well as elemental cell dimensions are considered, what made them attractive for investigations of electrocatalytic activity towards hydrogen electrode reactions. Tungsten carbide (WC) shows similar properties as platinum, considering electronic properties and hydrogen chemisorption. However, obtained exchange current densities are still 2-3 orders of magnitude smaller than these on clean Pt-surfaces, limiting interests in WC to be applied as a catalyst support only. On the other side, synergy between Pt and WC-support in terms of increase of catalytic activity has been discussed in numerous studies, but its nature has not been completely clarified so far. Besides platinum itself, other platinum group metals are also attractive for investigations as part of similar systems, representing platinum-free catalysts. However, no systematic studies considering transition metal overlayers, prediction and explication of their catalytic activity, as well as stability in conditions of hydrogen electrode operation, have been published yet. In this work, thin layers of transition metals (Cu, Ru, Rh, Pd, Ag, Ir, Pt and Au) on WC support have been systematically investigated using Density Functional Theory (DFT). Special attention has been paid to Pd and Pt monolayer and bilayer, including factors determining metal-support interacton on the level of electronic structure. The research then has been extended to other transition metal monolayer systems, the correlation between metal-support binding energy and cohesive energy as intrinsic property of metals has been pointed out, and futher used to predict stability of systems which have not been examined experimentally so far. Hereinafter, the possibility to predict catalytic activity of surfaces from DFT calculations has been discussed, and the volcanic curve, correlating DFT calculated hydrogen adsorption energies with experimentally obtained exchange current densities, has been constructed, taking into account the simplicity and proved practical applicability of that approach. In particular, activity of Pd and Pt overlayers, the concept, as well as the origin of the synergy with WC-support, have been extensively discussed. On the other hand, among analyzed monolayers, CuML/WC and RhML/WC were the most interesting, because of their predicted catalytic activity practically equal to Pt(111). Neither of these systems has been examined yet as a catalyst for hydrogen electrode reactions, and CuML/WC has not even been prepared experimentally. Based on theoretical analysis of, basically thermodynamical, properties, the possibility to obtain these systems in UHV conditions, as well as expected stability in conditions of hydrogen electrode operation, have been pointed out. Finally, general reactivity trends have been considered from the point of view of hydrogen-substrate interactions, on the level of electronic structure, and the factors determining this interaction have been discussed. In general, results of this dissertation implied the possibility to obtain a new class of hydrogen electrode reaction catalysts, based on suitable combination of thin metal layer and the support, not containing platinum at all.en
dc.formatapplication/pdf
dc.languagesr
dc.publisherУниверзитет у Београду, Факултет за физичку хемијуsr
dc.relationinfo:eu-repo/grantAgreement/MESTD/Basic Research (BR or ON)/172045/RS//
dc.rightsopenAccessen
dc.rights.urihttps://creativecommons.org/licenses/by-nc/4.0/
dc.sourceУниверзитет у Београдуsr
dc.subjectvolfram-karbidsr
dc.subjecttungsten carbideen
dc.subjectelectrocatalysisen
dc.subjectelectronic structureen
dc.subjectmetal overlayersen
dc.subjectHER/HORen
dc.subjectmonolayeren
dc.subjecthydrogen evolutionen
dc.subjectvolcano curveen
dc.subjectelektrokatalizasr
dc.subjectelektronska strukturasr
dc.subjecttanki slojevi metalasr
dc.subjectHER/HORsr
dc.subjectmonoslojsr
dc.subjectizdvajanje vodonikasr
dc.subjectvulkanska krivasr
dc.titleTeorijska analiza svojstava volfram-karbida kao podloge u elektrokatalizatorima za reakcije vodonične elektrodesr
dc.titleTheoretical analysis of tungsten carbide properties as electrocatalyst support for hydrogen electrode reactionsen
dc.typedoctoralThesisen
dc.rights.licenseBY-NC
dcterms.abstractПашти, Игор; Марчета-Канински, Милица; Петковић, Милена; Васић Aнићијевић, Драгана; Теоријска анализа својстава волфрам-карбида као подлоге у електрокатализаторима за реакције водоничне електроде; Теоријска анализа својстава волфрам-карбида као подлоге у електрокатализаторима за реакције водоничне електроде;
dc.identifier.fulltexthttp://nardus.mpn.gov.rs/bitstream/id/21185/Vasic_Dragana_referat_FFH-23063.pdf
dc.identifier.fulltexthttps://nardus.mpn.gov.rs/bitstream/id/21185/Vasic_Dragana_referat_FFH-23063.pdf
dc.identifier.fulltexthttps://nardus.mpn.gov.rs/bitstream/id/21184/Disertacija3688.pdf
dc.identifier.fulltexthttp://nardus.mpn.gov.rs/bitstream/id/21184/Disertacija3688.pdf
dc.identifier.rcubhttps://hdl.handle.net/21.15107/rcub_nardus_5746


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