Crystal structure of platinum and iridium nanocomposite electrocatalysts

Kamšek, Ana Rebeka (author), Hodnik, Nejc (mentor), Dražić, Goran (comentor)

Hydrogen technologies present a promising alternative to internal combustion engines in the transportation sector and serve as a viable option for stationary power generation. Water electrolysis produces hydrogen, which can later be used in a fuel cell to generate clean electricity. The commercialization of hydrogen technologies faces challenges due to the high costs of proton exchange membrane water electrolyzers and fuel cells, which rely on expensive noble metals like platinum and iridium. Advanced functional nanomaterials with supported metal-based nanoparticles can be utilized to reduce these costs while maintaining good catalytic properties. The structural characteristics of an electrocatalyst significantly influence its catalytic activity and stability. Therefore, it is crucial to gain a deeper understanding of how its structure forms and evolves to interpret measurements and plan future syntheses. This dissertation examines the diversity of crystal structures in electrocatalysts that contain platinum or iridium-based nanoparticles on high-surface-area supports. It aims to clarify several specific aspects of the structure-property relationships of the materials studied. A key focus of this work is to develop a reliable methodology for analyzing experimental data. First, we examine the presence of anti-phase boundaries in carbon-supported PtCu3 nanoparticles. In the second part, we use 4D-STEM to determine and track the local crystal structure of carbon-supported PtCu3 nanoparticles through identical location imaging. Then, we track and quantify individual degradation mechanisms using STEM images of a Pt-Co/C electrocatalyst. Lastly, we examine how metallic nanoparticles on ceramic support are influenced by metal-support interactions.

• Language: English
• Keywords: electrocatalysis, nanoparticles, structure-property relationship, electron microscopy, data analysis
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2025
• PID: 20.500.12556/RUL-170176
• COBISS.SI-ID: 243819011
• Publication date in RUL: 02.07.2025

Secondary language

• Language: Slovenian
• Title: Kristalna struktura platinskih in iridijevih nanokompozitnih elektrokatalizatorjev

Abstract

Vodikove tehnologije so obetavna alternativa motorjem z notranjim zgorevanjem v prometu in hkrati primerna možnost za stacionarno proizvodnjo električne energije. Z elektrolizo vode se pridobiva vodik, ki se lahko kasneje uporabi v gorivni celici za proizvodnjo čiste električne energije. Visoka cena elektrolizerjev vode in gorivnih celic s protonsko izmenjalno membrano ostaja izziv za komercializacijo teh tehnologij. Naprave namreč uporabljajo elektrokatalizatorje, ki temeljijo na dragih žlahtnih kovinah, kot sta platina in iridij. Za zmanjšanje teh stroškov ob ohranjanju dobrih katalitskih lastnosti lahko uporabimo napredne funkcijske nanomateriale s kovinskimi nanodelci na nosilcu. Strukturne značilnosti elektrokatalizatorja pomembno vplivajo na njegovo katalitsko aktivnost in stabilnost, zato je za lažjo interpretacijo meritev in načrtovanje prihodnjih sintez ključnega pomena bolje razumeti, kako se oblikuje in spreminja njegova struktura. Ta disertacija preučuje raznolikost kristalnih struktur elektrokatalizatorjev, ki vsebujejo nanodelce na osnovi platine ali iridija na nosilcih z veliko površino. Cilj je razložiti nekaj vidikov odnosov med strukturo in lastnostmi preučevanih materialov. Ključen poudarek tega dela je razvoj zanesljive metodologije za analizo eksperimentalnih podatkov. Najprej preučimo prisotnost antifaznih mej v nanodelcih PtCu3 na ogljikovem nosilcu. V drugem delu z uporabo 4D-STEM na identični lokaciji opišemo in spremljamo lokalno kristalno strukturo nanodelcev PtCu3, podprtih na ogljiku. Nato s STEM slikami elektrokatalizatorja Pt-Co/C sledimo posameznim degradacijskim mehanizmom in njihov doprinos ovrednotimo. Nazadnje preučujemo, kako na kovinske nanodelce na keramičnem nosilcu vplivajo interakcije med kovino in nosilcem.

• Keywords: elektrokataliza, nanodelci, odnosi med strukturo in lastnostmi, elektronska mikroskopija, obdelava podatkov