Controlled routes to aluminium-containing alloys from molecular precursors

Lead Research Organisation: University of Oxford
Department Name: OxICFM CDT

Abstract

A number of important chemical processes are electrolytic, meaning that they are driven by passing electricity through the reaction mixture. Often, materials which increase the rate of these processes (electrocatalysts) are used to improve the energy efficiency and capacity of the process, but these materials commonly contain so-called 'noble metals' such as palladium or iridium. Noble metals are scarce and expensive, and so it can be challenging to carry out these processes at the large scales required industrially. One such process is the electrolytic conversion of water to hydrogen and oxygen. Hydrogen gas is an important product due to its viability as a 'green' fuel, and so its efficient production is becoming ever more crucial as we seek to move away from traditional carbon-based fuels. It is therefore necessary to find effective new electrocatalysts which contain cheaper and more abundant metals so that hydrogen production may more easily be carried out at the large scales required.
One potential class of materials are alloys (metals containing a mixture of elements) of aluminium (the most abundant metal in the earth's crust) with base metals (such as iron or manganese). These alloys are challenging to synthesise due to aluminium's very low melting point, so alternative routes are required. One option is to synthesise molecular compounds containing an Al-M bond which decompose at high temperatures to form the desired alloy. Such compounds (referred to as Single Source Precursors or SSPs) allow us to generate otherwise inaccessible materials.
One challenge this approach poses is in finding a systematic means of synthesising a range of Al-M bonded compounds for a variety of metals. Such compounds exist for a few select metals, but their syntheses isn't readily generalisable (so fewer possible electrocatalyst materials can be made and tested), and the Al-M bonds are often weak, so they may not be suitable for thermal generation of an alloy. The recent discovery of a new class of compound, aluminyls, which feature an anionic (negatively charged) aluminium atom supported by an organic scaffold, offers a solution. This type of compound is suitable for reaction with a large range of other metal compounds, and so offers a general route to a wide range of SSPs containing strong (covalent) Al-M bonds.
The aim of this project is therefore to use these aluminyl compounds (and potentially related gallium and indium analogues) to synthesise a broad library of SSPs containing a variety of base metals. These compounds will be studied to provide insight into their chemical behaviour, before exploring their conversion into aluminium containing alloys by thermal decomposition. These alloys will be analysed to determine their exact composition and surface structure, and finally tested as electrocatalysts to compare their performances with those of traditional noble metal materials.
The use of aluminyl and related systems as a means of accessing this class of compound, as well as their subsequent conversion into potentially active alloys, is a novel approach within this field.
This project falls within the EPSRC manufacturing the future research area.
This project will involve collaboration with both the Moody group from the Department of Materials at the University of Oxford (for the analysis and characterisation of alloy material) and with the Driess group from the Department of Chemistry at TU Berlin for the investigation of electrocatalytic activity.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023828/1 01/04/2019 30/09/2027
2404136 Studentship EP/S023828/1 01/10/2020 30/09/2024 Liam Griffin