Ultra-small Metal Particles for the Storage and Conversion of CO2, CH4 and H2

The present project proposes a new approach to replace fossil fuels by man-made ones using ultra-small metal particles.

Our current energy needs are met by fossil fuels. This approach however is unsustainable owing to the different timescales of fuel production and combustion, the latter of which also generates greenhouse gases, changing the climate globally. On the other hand, uneven occurrence and distribution of sustainable energy sources, such as solar or wind power, warrants energy storage. Nature stores the Sun's energy as reduced carbon, e.g. coal, oil and gas. The present proposal will also employ this approach.

Context
Heterogeneous catalyst activity is dependent on the catalyst's surface area. With decreasing catalyst size, the surface-to-volume ratio increases, leading to improved activities. This could lead to the assumption that single atoms have the highest catalytic activity. However, size reduction may also alter the materials' physical and chemical properties related to the delocalisation of free electrons. Chemical reactivity of transition-metals is not only dependent on the atom numbers in a cluster but also on their arrangement, i.e. shape, owing to the spatial properties of d orbitals. In order to design transition-metal catalysts with selective and enhanced catalytic activity, it is thus crucial to establish the relationship between particle geometry and reactivity.

Aims and Objectives
The proposed project, will focus on ultra-small transition-metal particles, in the 1-50 atom range, supported on highly porous metal-organic frameworks. The particles' geometry-catalytic activity relationship will be explored for the conversion of feedstock harvested from air (CH4 and CO2) and water (H2) into synthetic fuels.

The proposed project will first develop methods to synthesise shape- and size-controlled ultra-small metal particles using metal-organic frameworks as templates. The greatest challenge is identified as increased surface energy, a consequence of the increased surface-to-volume ratio. High surface energy in turn compromises the thermodynamic stability of particles and renders their size control difficult. Geometry control of the ultra-small transition-metal particles will be achieved by establishing strong metal-support interactions by i) preliminary computational calculations in collaboration with Prof Thomas Heine and ii) the application of metal-organic frameworks with chemical functionalities capable of selective host-guest interactions, which is herein proposed for the first time.

Subsequently, the activity of the stable ultra-small transition-metal catalysts will be explored for the conversion of methane into longer chain hydrocarbons, the conversion of carbon dioxide through reduction with H2 (or CH4) and the activation and storage of hydrogen under mild conditions. Thanks to the PI's experience in both the functionalisation of metal-organic frameworks and their application as support for metal nanoparticles, together with her unique skillset in coordination and physical chemistry, and gas technologies, she is ideally placed to carry out this interdisciplinary and ambitious research.

Applications and Benefits
The particles will have various properties depending on their size and shape and will be exploited for ambient-temperature hydrogen storage, and the catalytic conversion of carbon dioxide, methane and hydrogen. Synthesis of fuels from pollutants such as CO2 and CH4 will reduce atmospheric pollution and convert them into more valuable chemicals while making use of already existing distribution infrastructures. The development of renewable, low-carbon energy carriers will benefit our society for energy security and the reduction of atmospheric pollutant levels.

The proposed project will also accrue technology for gas sensing, drug delivery, electronics, water purification, gas separation, and in fuel cell and battery research.

The proposed research aims at developing a new methodology to convert feedstock harvested from air and water (CO2, CH4 and H2) into synthetic fuels, using supported ultra-small transition-metal catalysts.
Apart from the immediate scientific and technological impact of the development of reliable techniques to control the geometry of particles, the proposed research will also have an impact on the societal level. Energy security and decreasing greenhouse-gas levels are both very important for our society to solve. In the long term, the proposed project will enable technologies to convert carbon dioxide and methane into synthetic fuels, thereby both decreasing their atmospheric levels while using sustainable sources (waste). Also, by tackling hydrogen production, stationary hydrogen storage and hydrogen activation, a completely green energy carrier will be promoted.

The analysis of beneficiaries and stakeholders of the proposed project is presented below:

- The commercial private sector will benefit from the proposed research directly in the long term as the synthesis of fuels under mild conditions can be economically viable and thus will create employment. In addition, as the
synthetic method relies on feedstock harvested from air and water, there are no geographic limitations and so both production and profit can be kept in the United Kingdom.
- Policy makers and government agencies will benefit from the proposed research indirectly in the long term as the transition to synthetic fuels from mined fossil fuels will create energy security, as no geographic limitations and
thus no geopolitical issues are involved, and it will also reduce atmospheric greenhouse gas levels, easing strains on extreme-weather measures and also on health care.
- The proposed project features a collaboration with a museum, which will benefit from the project directly in the short term through public engagement events.
- The wider public will benefit from the proposed research indirectly in the long term as the reduction of atmospheric pollutants and greenhouse gas levels will result in better quality of life and better health. The foundation of
new companies will create wealth and employment, which will also be of the benefit of the wider UK and global society.

Through the conversion of atmospheric pollutants into synthetic fuel using hydrogen generated from water via sustainable methods such as direct photolysis, both national health and wealth will improve. Particulars include reducing the impact of climate change and foundation of new businesses.

It should be mentioned that in order for this transition to take place, efficient and viable methods for the separation of atmospheric pollutants from air need to be developed and further scientific advances in direct water photolysis or photovoltaics are needed. If these pre-requisites are met the proposed project will have a high and important impact on both economy and society.

An important impact of the proposed project and in particular the public engagement activities included will be the shifting of public perception of atmospheric pollutants such as carbon dioxide from waste to potential feedstock. This will also enable to revise our society's general perception of waste materials. This is one of the greatest challenges of the 21st century and while some things can be regulated by policies the best solution to tackle waste management is to encourage approaches to re-using and not discarding wastes.

The time scales involved in the impact of the proposed research are typically longer than the project itself. It is expected that perceptible economic and societal impact of the project would take 10-15 years.

The MSc student will acquire technical skills, which he or she will be able to apply in the industry, while the management, leadership and communication skills acquired by the PI through the project could be applied in all employment sectors.