Ionic-Liquid Mixtures: from Surface Structure to Catalytic Performance

Ionic liquids (ILs), with their unique combination of properties and wealth of potential applications, have captured the imagination of a large community of scientists in recent years. Fundamental studies on ILs have led to breakthroughs in our understanding and have enabled the development of ILs that are promising candidates for use in areas such as catalysis, carbon-capture and storage (CCS), biomass processing, as electrolytes in batteries, supercapacitors and dye-sensitised solar cells and more.

This project aims to develop and utilise a wide range of experimental and computational methodologies to investigate the surface, and bulk, structure of IL mixtures that are currently poorly understood and consequently underutilised. We previously developed a novel technique that can probe liquid interfaces with direct chemical specificity, Reactive-Atom Scattering - Laser-Induced Fluorescence (RAS-LIF), and used it to detect H (or D)-containing functional groups at IL interfaces. We will extend its applicability to new chemical functionalities, in particular fluorinated species, by using high-energy Al-atoms as reactive probes of fluorinated functionality (on both cations and anions) at IL surfaces. This will be complemented by new capabilities for studying liquid surfaces by X-ray and neutron reflectivity under catalytically relevant conditions, and by bulk structure/property studies. The detailed understanding developed will lead to structure-property relationships in IL mixture systems that will be used in the final stages of the project in supported IL phase (SILP) catalysis and will support the deployment of new and bespoke functional ILs for catalysis in SILP systems. This ambitious project aims to cover the whole pipeline of IL development from preparation, to structural understanding, and then to industrially relevant applications.

The primary motivation of this proposal is improved fundamental understanding of the chemical structure of the gas-liquid interface of ionic liquids, particularly those involving fluorous functionalities, which have significant potential in practical catalysis e.g. Supported Ionic Liquid Phase (SILP) catalysis.

We expect this work to have the following impacts on the wider scientific community.
(i) We will develop a new reactive atom scattering (RAS) laser-induced fluorescence (LIF) methodology, based on reactive metal atoms, that is sensitive to the presence of C-F (and potentially C-H or S=O/C=O) groups at a liquid surface. We expect that the demonstration of this wider chemical applicability of the RAS-LIF technique will encourage its take-up more widely within the surface-science community, for example the ability to detect C=O functionality could have applications in atmospheric aerosol studies.
(ii) We will design and build a new high-T, high-P experiment for in operando liquid-surface reflectivity measurements capable of working with both neutrons (ISIS) and X-rays (Diamond), with the intention, in conjunction with the Catalysis Hub, to make it available to the wider scientific community.
(iii) Provide a comprehensive and fundamental understanding of the gas-liquid interface in IL mixtures containing fluorinated groups and/or functional units such as ligands or organometallic catalysts.

Exploitation of new IL mixtures in catalysis will have an impact on the UK economy. Novel IL mixtures and/or SILPs, which enhance catalytic activity, selectivity and/or stability over those currently in use, will allow new routes to more efficient (i.e. lower cost and/or more sustainable) production of chemical feedstocks that underpin areas of great industrial importance to the UK economy (e.g. pharmaceuticals, agrochemicals, materials). This also provides a societal benefit, as enhanced industrial catalysis will be more effective, sustainable and environmentally benign. We also intend through this project to raise levels of scientific awareness within the general public, focused on the development of neoteric solvents and industrial catalysis.

Finally, the two PDRAs employed on this project represent a particularly valuable form of highly trained personnel. They will develop or extend a very broad expertise in experimental and computational methods, gaining insight across a range of physical and synthetic chemistry. They will enhance their transferable problem-solving, presentation and communication skills, and will gain experience of working in an interdisciplinary and highly collaborative environment. They will be ideally placed to become successful independent investigators, who have significant potential to play leadership roles in academia or high technology industry, enhancing growth and sustainability in the UK economy.