The interfacial catalyst
INVITATION
ESRF COLLOQUIUM
"The interfacial catalyst"
Friday, October 28th, 14:00
Presented by Michele Parrinello, Istituto Italiano di Tecnologia, Genova
Venue: ESRF Auditorium and Zoom
Abstract
The transition to a green economy depends crucially on the development of efficient catalytic processes. Understanding and modelling these processes is therefore of paramount importance. However, the industrial production of commodity chemicals requires extreme conditions of temperature and pressure. This poses a severe challenge both to theoreticians and experimentalists. Several aspects of industrial catalysis suggest that the standard static approach to catalysis based on the identification of static catalytic sites is not applicable. For instance, in the industrial reactor the catalyst remains active for quite a long time, notwithstanding the harsh operating conditions. To explain the long-term stability of industrial catalysts we invoke instead a fully dynamical scenario. We illustrate this concept with a simulation of the Li2NH catalyzed decomposition of ammonia at T = 750 K, a process that has been intensively studied for its possible use in a hydrogen-based economy. These simulations are made possible by recent developments in ab-initio molecular dynamics simulations. We show that, when exposed to the reactant a dynamical fluctuating steady state is set up at the Li2NH surface. In this environment a series of reactions that eventually leads to the release of N2 and H2 molecules become possible. It is this interfacial state that is the catalyst and not this or that static atomic arrangement. This insight will be precious in the design of novel catalyst.
The transition to a green economy depends crucially on the development of efficient catalytic processes. Understanding and modelling these processes is therefore of paramount importance. However, the industrial production of commodity chemicals requires extreme conditions of temperature and pressure. This poses a severe challenge both to theoreticians and experimentalists. Several aspects of industrial catalysis suggest that the standard static approach to catalysis based on the identification of static catalytic sites is not applicable. For instance, in the industrial reactor the catalyst remains active for quite a long time, notwithstanding the harsh operating conditions. To explain the long-term stability of industrial catalysts we invoke instead a fully dynamical scenario. We illustrate this concept with a simulation of the Li2NH catalyzed decomposition of ammonia at T = 750 K, a process that has been intensively studied for its possible use in a hydrogen-based economy. These simulations are made possible by recent developments in ab-initio molecular dynamics simulations. We show that, when exposed to the reactant a dynamical fluctuating steady state is set up at the Li2NH surface. In this environment a series of reactions that eventually leads to the release of N2 and H2 molecules become possible. It is this interfacial state that is the catalyst and not this or that static atomic arrangement. This insight will be precious in the design of novel catalyst.
partners
European Synchrotron Radiation Facility - 71, avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France.