Functional Metal-Nitrogen-Hydrogen Systems

Chemistry is at the heart of many of the great technological transformations of the modern era. The urgent transition away from energy-dense but environmentally-damaging fossil fuels presents a new grand challenge for chemistry, centred on the design of materials associated with the conversion, distribution and utilisation of energy. In particular, the rapid expansion of solar and wind power will necessitate the use of large-scale energy storage, spanning wide ranges of energy, power and storage duration in diverse applications including domestic power, transportation and grid management.

In order to meet this challenge, we must leverage existing technology while simultaneously developing new materials with enhanced properties. The research programme contained within this Fellowship application details a plan to develop a new family of inorganic metal-nitrogen-hydrogen (M-N-H) materials, with an emphasis on their application to sustainable energy storage. At the core of this project is a synthetic programme which aims to significantly expand the range of M-N-H materials, moving beyond these first examples to systems which display a wider range chemical bonding types and metals.

Consideration of the application of M-N-H materials has been largely restricted to the Group I and II metal amides and imides (NH2- and NH2- bearing inorganic salts) in the context of lightweight hydrogen storage materials. More recently, these same materials have been identified as effective ammonia decomposition catalysts, and have been implicated in the enhanced ammonia synthesis activity of hydride-based composite catalysts. Ammonia is increasingly considered as a viable high energy density fuel and hydrogen carrier, and the catalytic activity of M-N-H materials may help promote its use. One theme of this fellowship will therefore be the expansion of the relatively small number of materials have been tested for their catalytic activity. Screening of the new M-N-H materials would not only result in the development of more active catalysts, but also a more complete understanding of the properties which govern their catalytic action.

Many functional materials are based on oxides, and property variation comes from varying the array of cations in the oxide material. Imide anions are similar to oxide, and so offer a path to creating analogous materials. For example, lithium oxide and lithium imide are isostructural, yet lithium imide shows ionic conductivity which is dramatically enhanced compared to the oxide. This part of the programme will seek to elucidate the relationship between imides and oxides, and to use this principle as a guide for the design of new imide-based functional materials. In particular, synthesis of imides with high ionic conductivity and electrochemically-active components (e.g. cathode materials) will be pursued with the goal of developing a concept imide battery material. The aim is to provide new insights into the fundamental chemistry of the M-N-H family and illustrate new approaches for the design of energy storage materials.

The research programme detailed in this Fellowship aims to contribute to the challenge of transitioning to a renewables-based energy system by developing a range of new energy storage materials based on metal-nitrogen-hydrogen systems. It aims to i) promote the hydrogen economy through facilitating the use of ammonia as a fuel and hydrogen carrier and ii) to generate a new family of electrochemical energy storage materials. Cheap and effective energy storage is one of the key technologies which can enable a complete transition to renewable energy and sustainable transportation, and so the potential for high-level impacts of projects in this area are clear.

The results of this programme are relevant across a broad range of interest groups:

1) Academic researchers will use the results of the work as the basis for further exploration of the potential functions of M-N-H materials; impact in these groups will be achieved by communicating the results of the project through academic journals, conferences and collaborative networks. The establishment of research networks through the collaborative research included in the proposal will facilitate creative approaches in future collaborative projects.

2) It is anticipated that intellectual property and commercial-scale demonstrations will be of significant interest to industrial groups which are active in hydrogen-based fuel and electrochemical energy storage. Commercial projects which result from intellectual property developed from the research will provide benefit to the UK through the technological advances enabled by the new materials.

3) The programme seeks to raise the profile of ammonia-based energy and highlight its readiness to provide a significant contribution to decarbonisation. This context is critically important to policy-makers as they consider the best ways to foster innovation and accelerate the transition to a sustainable energy system. Impact with the general public will also be achieved through the use of social media, lay-summaries of research articles promoted through a website and the University, and direct outreach activities.