doktorska disertacija
Luka Pavko (Author), Miran Gaberšček (Mentor), Marjan Marinšek (Thesis defence commission member), Nejc Hodnik (Thesis defence commission member), Anton Kokalj (Thesis defence commission member), Boštjan Genorio (Co-mentor)

Abstract

Vodikova ekonomija je obetavna rešitev svetovnih energetskih in okoljskih izzivov, pri čemer imajo gorivne celice ključno vlogo pri omogočanju čiste in učinkovite pretvorbe energije. Vendar pa je za široko uporabo gorivnih celic, zlasti gorivnih celic s protonsko prevodno membrano (angl. proton exchange membrane fuel cell – PEMFC), potrebna dodatna optimizacija katalitskih materialov, da se izboljšajo zmogljivost, vzdržljivost in ekonomičnost. Eden glavnih izzivov v tehnologiji gorivnih celic je katodna reakcija redukcije kisika (angl. oxygen reduction reaction – ORR), kjer se kot katalizator običajno uporabljajo nanodelci platine (Pt) podprti na ogljikovem nosilcu. Zagotavljanje zadostne stabilnosti takšnih nanokompozitov pa je še vedno velik izziv. Katalizatorji na osnovi Pt v obratovalnih pogojih gorivne celice degradirajo zaradi elektrokemijsko induciranega raztapljanja Pt in korozije ogljikovega nosilca. Za reševanje teh izzivov ta disertacija obravnava derivate grafena kot potencialne alternative trenutnim ogljikovim nosilcem na osnovi črnih ogljikov (angl. carbon blacks – CB) za izboljšanje stabilnosti in zmogljivosti katalizatorjev v PEMFC. V prvem delu disertacije se osredotočam na nov in inovativen postopek sinteze za pripravo kompozitnih elektrokatalizatorjev nanodelcev Pt na derivatih grafena. Najprej smo uporabili Hummersovo metodo za sintezo oksidiranih derivatov grafena. Nato smo uporabili pulzno zgorevalni reaktor v kombinaciji z metodo dvojne pasivacije z galvansko izmenjavo za pripravo Pt katalizatorjev na osnovi derivatov grafena. Ta metoda omogoča proizvodnjo večgramskih količin visokozmogljivih katalizatorjev, z visoko vsebnostjo kovin in visoko elektrokemijsko aktivno površino (angl. electrochemically active surface area – ECSA). S pospešenimi degradacijskimi testi smo pri sintetiziranih naprednih katalizatorjih preverjali elektrokemijsko stabilnost, ki je presegla stabilnost tradicionalnih katalizatorjev podprtih na CB. Med testiranjem stabilnosti smo izvedli tudi poglobljeno študijo rentgenske fotoelektronske spektroskopije (angl. X-ray photoelectron spectroscopy – XPS) da bi raziskali kemijske lastnosti ogljikovih nosilcev in jih povezali z opaženimi trendi stabilnosti. Poleg tega smo preizkusili zmogljivost pri visokih tokovnih gostotah v plinsko difuzijski elektrodi (angl. gas diffusion electrode – GDE), pri čemer smo dosegli zmogljivost, primerljivo komercialni referenci, in rekordno zmogljivost na področju derivatov grafena. Da bi dobili globlji vpogled v stabilnost naših katalizatorjev, smo izvedli in-situ meritve korozije ogljika z uporabo elektrokemijske celice sklopljene z masnim spektrometrom (angl. electrochemical cell coupled mass spectrometer – EC-MS). Rezultati so potrdili višjo stabilnost Pt katalizatorjev, podprtih z derivati grafena, kar dodatno potrjuje njihov potencial za uporabo v gorivnih celicah. V zadnjem delu disertacije smo izvedli študijo dopiranja z uvedbo heteroatomov bora (B) in dušika (N) v ogljikov nosilec. Namen te raziskave je bil še bolj povečati stabilnost katalizatorja. Na Pt katalizatorjih na dopiranih derivatih grafena, smo opravili stabilnostne teste. Rezultati so pokazali nepričakovan negativen učinek na stabilnost katalizatorjev, vendar pa je to odprlo nove možnosti za nadaljnje raziskave. Za boljše razumevanje vpliva dopantov na stabilnost katalizatorja bomo v prihodnjih raziskavah izvedli dodatna testiranja. Naša raziskava je pokazala potencial uporabe derivatov grafena kot naprednih nosilcev za binarni platinski katalizator v gorivnih celicah. Inovativni postopek sinteze, ki temelji na metodi pulznega zgorevanja, je omogočil proizvodnjo visoko zmogljivih in stabilnih katalizatorjev v velikih količinah. Obetavni rezultati te študije odpirajo nova obzorja za praktično uporabo derivatov grafena v tehnologiji gorivnih celic in prispevajo k napredku čistih in učinkovitih sistemov za pretvorbo energije.

Keywords

gorivne celice;protonska prevodna membrana;PEMFC;Pt-zlitine;PtM;ogljikovi nosilci;derivati grafena;reakcija redukcije kisika;ORR;doktorske disertacije;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher: [L. Pavko]
UDC: 620.1:621.352.6(043.2)
COBISS: 176928515 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Graphene and its derivatives as an advanced binar platinum catalyst supports in fuel cells
Secondary abstract: The hydrogen economy has emerged as a promising solution to address the global energy and environmental challenges, with fuel cells playing a crucial role in enabling clean and efficient energy conversion. However, the widespread adoption of fuel cells, particularly in polymer electrolyte membrane fuel cells (PEMFCs), requires the optimization of catalyst materials to enhance performance, durability, and cost-effectiveness. One of the major challenges in fuel cell technology lies in the cathode oxygen reduction reaction (ORR), where carbon-supported platinum (Pt) nanoparticles are commonly used as the catalyst. However, providing sufficient durability of such catalyst nanocomposites remains a significant challenge. Under operating conditions Pt-based catalysts suffer from degradation due to electrochemically-induced Pt dissolution and carbon support corrosion. To address these challenges, this disertation explores graphene derivatives as potential alternatives to current carbon black (CB) supports in order to improve the durability of PEMFC catalysts under operating conditions. In the first part of the thesis we focus on a novel and innovative synthesis procedure to prepare graphene derivative-supported Pt catalysts. First, we utilized the Hummers method to produce oxidized versions of graphene derivatives. Subsequently, we employed the pulse combustion method in combination with the double galvanic displacement method to prepare graphene derivative-supported Pt catalysts. This scalable method enables the production of multigram quantities of high-performance catalysts in high quantities, with high metal loading and electrochemically active surface area (ECSA). Through accelerated degradation tests, these advanced catalysts were thoroughly examined for their electrochemical durability, surpassing the performance of traditional CB-supported catalysts. During the durability testing, we also conducted a thorough X-ray photoelectron spectroscopy (XPS) study to investigate the chemical properties of the carbon supports and correlate them with the observed durability trends. Furthermore, we tested the high current density performance in gas diffusion electrode (GDE) achieving performance comparable to comercial reference and record performance in the field of graphene derivatives. To gain deeper insights into the durability of our catalysts, we conducted in-situ carbon corrosion measurements using electrochemical cell coupled with mass spectrometer (EC-MS). The results confirmed the enhanced durability of the graphene derivative-supported Pt catalysts, further validating their potential for application in fuel cells. In the last part of the disertation, we conducted a dopant study by introducing Boron (B) and Nitrogen (N) functionalities to the carbon support. This investigation aimed to enhance the catalyst's stability even further. The doped graphene derivative-supported Pt catalysts were subjected to durability testing. The results reveal unexpected negative effect on the durability of the graphene derivative-supported Pt catalysts. However, this initial observation has opened a new avenue for further investigation. To gain a deeper understanding of the impact of dopants on catalyst durability, additional comprehensive testing will be conducted in future research. Our research has demonstrated the potential of graphene derivatives as advanced binary platinum catalyst supports in fuel cells. The innovative synthesis procedure based on the pulse combustion method has enabled the production of durable and high-performance catalysts in large quantities. The promising outcomes of this study open new horizons for the practical application of graphene derivatives in fuel cell technology, contributing to the advancement of clean and efficient energy conversion systems.
Secondary keywords: proton exchange membrane fule cell;oxygen reduction reaction;Pt-alloys;carbon support;graphene derivatives;Grafen;Disertacije;
Type (COBISS): Doctoral dissertation
Study programme: 1001051
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, smer Kemijsko inženirstvo
Pages: VII, 121 f.
ID: 20880733