Mono- and bimetallic nanoparticles stabilized by functionalized ionic liquids: Synthesis and catalytic application
Metal nanoparticles (NPs) are fascinating materials with a size between 1-100 nm (10-9 m), but due to their high surface-to-volume ratio they tend to agglomerate and grow larger. To counter this, a stabilizing agent can be used to modify their surface properties and prevent them from agglomerating, while maintaining most of their inherent high surface. This is important as it allows the metal NPs to be employed in applications such as catalysis, where a high surface is desirable. Here, the stabilizers can also optimize the reactivity and improve the selectivity of the metal NPs towards a particular product during a reaction. Ionic liquids are a special class of liquids composed entirely of positive and negative ions possessing intriguing physical and chemical properties, such as being non-volatile, highly thermal stable, large electrochemical window, ability to dissolve a wide range of substrates, among others. Importantly, they can further be designed to contain different functional groups (e.g., nitrile, hydroxyl, methoxy etc.). This is preferentially done through a so-called organometallic approach, where an organometallic complex with low-valent metal (e.g., [Ru(COD)(COT)] or [Ni(COD)2]) is decomposed at mild conditions with hydrogen in the presence of a stabilizer (ionic liquid) to obtain metal NPs with different sizes and properties.
This PhD thesis explores the reactivity of ruthenium, nickel and ruthenium-rhenium bimetallic NPs synthesized by the organometallic approach using carefully selected ionic liquids. Complete characterization of these metal NP/IL systems have been performed using state-of-art characterization techniques, which have provided keen insights into the interaction between the NP surface and ionic liquids. The structure-performance relationship was further studied by employing them in the catalytic hydrogenation of a variety of substrates like styrene, 2-cyclohexen-1-one, 2,3-benzofuran etc.
Principal Supervisor:
Professor Anders Riisager,
DTU Chemistry
Co-supervisor:
Dr. Karine Philippot, French National Centre for Scientific Research, Toulouse
Dr. Rosa Axet, French National Centre for Scientific Research, Toulouse
Professor Søren Kegnæs, DTU Chemistry
Examiners:
Professor Jens Øllgaard Duus, DTU Chemistry
Professor Jairton Dupont, Universidade Federal do Rio Grande do Sul, Brazil
Professor Karine De Oliveira Vigier, Université de Poitiers, France
Chairperson:
Senior Researcher Jerrik Mielby, DTU Chemistry