Exploring the limits: A low-pressure, low-temperature Haber-Bosch process

Aleksandra Vojvodic, Andrew James Medford, Felix Studt, Frank Abild-Pedersen, Tuhin Suvra Khan, Thomas Bligaard, Jens K. Nørskov
Year of publication: 
Chemical Physics Letters

The Haber–Bosch process for ammonia synthesis has been suggested to be the most important invention of the 20th century, and called the ‘Bellwether reaction in heterogeneous catalysis’. We examine the cat- alyst requirements for a new low-pressure, low-temperature synthesis process. We show that the absence of such a process for conventional transition metal catalysts can be understood as a consequence of a scaling relation between the activation energy for N2 dissociation and N adsorption energy found at the surface of these materials. A better catalyst cannot obey this scaling relation. We define the ideal scal- ing relation characterizing the most active catalyst possible, and show that it is theoretically possible to have a low pressure, low-temperature Haber–Bosch process. The challenge is to find new classes of cat- alyst materials with properties approaching the ideal, and we discuss the possibility that transition metal compounds have such properties.

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