The rapid rise in the concentration of atmospheric CO2 over the past century has increased demand for alternative fuel sources to address climate change. Even a climate progressive nation such as the UK is currently failing to meet CO2 emission targets set by the Paris Agreement,1 hence there is significant pressure for the development of innovative technologies to overcome this global challenge. The UK government's target to reach net-zero emissions by 2050 is to be partly facilitated by carbon sequestration. The UK's largest carbon capture plant, due to be operational by 2021, hopes to capture 40,000 tonnes of CO2 per annum - equivalent to the emissions of 22,000 cars.

Both commercial and industrial applications of carbon dioxide are relatively limited, therefore these soon to be vast stores of captured CO2 present an exciting opportunity for an alternative fuel source. This project aims to develop metal nanoparticle catalysts that will facilitate both the thermal and photocatalytic reduction of CO2 to more valuable products such as formic acid which can serve as a hydrogen storage material, methanol which can act as a combustion fuel or as a C1-feedstock for the production of various fine chemicals, methane or even higher alkanes.

The principal focus of this work will be to employ functionalized polymer immobilized ionic liquids (PIIL) as supports to stabilize gold nanoparticles, control their growth (size distribution and shape), modify surface electronic properties and explore whether catalyst-support interactions can be used to control efficacy. PIIL supports are advantageous over bespoke ligands as they are more affordable, robust, and are not prone to leaching enabling the catalyst to be recovered and recycled. The Doherty group has previously found that PIIL supports are highly beneficial in promoting the activity, stability, and selectivity of gold nanoparticle catalysts towards the reduction of small molecules.2 Reports have shown that polymeric ionic liquids also have a high CO2 absorption capacity in addition to fast rates of CO2 adsorption/desorption,3 therefore we intend to extend this technology towards the thermal and light driven reduction of CO2. Advanced analytical techniques such as TEM, XPS, EDX, powder-XRD, TGA and solid-state NMR spectroscopy will be utilized to determine the catalyst composition while DRIFT, XPS and in situ FTIR will be used to probe the catalyst surface and to study CO2 adsorption. A detailed understanding of surface-support interactions will provide insight on the factors that influence catalyst activity and product distribution, facilitating the development of an optimum catalyst with a stable activity profile suitable for scale-up.

Relevant EPSRC research areas: Catalysis, Materials for Energy Applications, Carbon Capture and Storage, Renewable Energy
1. Anderson, K.; Broderick, J. F.; Stoddard, I., A Factor of Two: How the Mitigation Plans of 'Climate Progressive' Nations Fall Far Short of Paris-Compliant Pathways. Clim. Policy 2020, 1-15.
2. Doherty, S.; Knight, J. G.; et al., Highly Selective and Solvent-Dependent Reduction of Nitrobenzene to N-Phenylhydroxylamine, Azoxybenzene, and Aniline Catalyzed by Phosphino-Modified Polymer Immobilized Ionic Liquid-Stabilized AuNPs. ACS Catal. 2019, 9 (6), 4777-4791.
3. Zulfiqar, S.; Sarwar, M. I.; Mecerreyes, D. Polymeric Ionic Liquids for CO2 Capture and Separation: Potential, Progress and Challenges. Polym. Chem. 2015, 6 (36), 6435-6451.