Engineering plasmonic bimetallic nanostructures for energy conversion

Herran, Matias (2023): Engineering plasmonic bimetallic nanostructures for energy conversion. Dissertation, LMU München: Fakultät für Physik

Abstract

A new class of photocatalysts gathering both optical and heterogeneous catalysis principles can be produced by combining plasmonic nanoparticles with catalytic metals. In this configuration, chemical reactions taking place in the catalytic comoonent are powered by the visible light focused by plasmonic nanoparticles. Understanding how energy is transferred from the plasmonic to the catalytic reactive center, necessary to maximize the benefits of this combination, is one of the main concerns of these hybrids. Excited carriers, electromagnetic fields, and even heat are essentially the means by which the energy can be delivered to the reactive center. These pathways strongly depend on how the materials interact; for instance, charge transfer or heat transfer pathways require the presence of an interface, while other pathways need the construction of a gap between the components. It is central to determine which of these pathways modulates the performance of plasmonic bimetallic photocatalysts in order to obtain the maximum efficiency on converting light into chemical energy. In this regard, the following aspects of plasmonic bimetallic systems were investigated in the course of this thesis: • The structure-performance correlation • Ability to convert light into heat • The transition from a colloidal suspension to a 2D planar configuration with optimized geometry, boosting the light-catalyst interaction. Our observations point out that those structures in which the catalytic metal is positioned at sub-nanometer distance with respect to the plasmonic nanoparticle (antenna-reactor), are able to produce a higher boost in reaction rates. In addition to the little detriment of the optical properties, the plasmonic nanoparticles are able to increase the otherwise small absorption of the catalytic metals in the visible range via optical hotspots formation. As a result of the interaction with light, excited carriers are generated in proximity to the adsorbate-reactor interface, where can be utilized for the adsorbed molecules to facilitate their transformation. Thermal analysis proved that the plasmonic antenna’s heat output is insufficient to account for the reaction boost at solar irradiances, which allowed us to conclude that the excited carriers are a significant factor in the rate enhancement. Finally, the preferred conformation was extended as a 2D supercrystal offering a large density of hotspots which catalytic metals can take advantage from. When testing this structure for Formic Acid dehydrogenation, it resulted in one of the largest production reported so far for this H2 carrier.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Plasmonic, Energy conversion, bimetallics, sunlight-driven catalysis, catalysis
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 29. März 2023
• 1. Bericht­erstatter:in: Cortes, Emiliano