First principles design of novel ammonia synthesis catalysts

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The development of the Haber Bosch Process for the synthesis of ammonia on an industrial scale was one of the major achievements of the 20th Century. It can be directly credited with sustaining the global population through the provision of an accessible route to synthetic fertilizers. The process is based upon the reaction of pure N2 and H2 feedstreams over a promoted iron based catalyst. It is operated at high pressure (>100 atmospheres) and moderate temperature and the process as a whole currently accounts for a significant proportion of global energy demand (>1%). In this research, we are attempting to develop alternative catalysts which will contribute to energy savings by facilitating the reaction at lower reaction temperatures (where there is a thermodynamic advantage.) The approach to be taken will involve a mixture of computational design and experimental testing and is based upon previous studies of metal nitride catalysts which exhibit interesting activity for ammonia synthesis. Metal nitrides potentially contain "activated" nitrogen within their structure and it is the reactivity of this lattice nitrogen which which could be the key to their high activity. Using computational modelling, understanding of experimental results will be obtained and will be extended to the identification of nitride materials of potential high catalytic activity. In parallel laboratory experiments, the identified materials will be synthesised and tested and the results fed back into the computational modelling to provide improved understanding. In this way, optimal catalyst formulations will be identified and these will be prepared and tested under industrially relevant ammonia synthesis conditions and the results will be compared to those from conventional industrially applied iron based catalysts.