Abstract
Heterogeneous single-atom catalysts (SACs) hold the promise of combining high catalytic performance with maximum utilization of often precious metals. We extend the current thermodynamic view of SAC stability in terms of the binding energy (Ebind) of single-metal atoms on a support to a kinetic (transport) one by considering the activation barrier for metal atom diffusion. A rapid computational screening approach allows predicting diffusion barriers for metal–support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal (Ec). Metal–support combinations relevant to contemporary catalysis are explored by density functional theory. Assisted by machine-learning methods, we find that the diffusion activation barrier correlates with (Ebind)2/Ec in the physical descriptor space. This diffusion scaling-law provides a simple model for screening thermodynamics to kinetics of metal adatom on a support.
Highlights
Supported metals constitute an important class of heterogeneous catalysts widely used by the chemical and automotive industry, in controlling environmental pollution, and in energy conversion technology[1,2,3,4]
O’Connor et al employed machine learning to describe the stability of metal single atoms on oxide supports in terms of the binding energy[17]. We extended this thermodynamic approach by determining scaling relations for the activation barrier of diffusion of the single atom, which is the key kinetic step in the sintering process
Mavrikakis and co-workers found that the diffusion barrier of adsorbates such as atomic O and N and molecular CO species depends in a linear fashion on the corresponding adsorption energies on transition metal surfaces[42]
Summary
Supported metals constitute an important class of heterogeneous catalysts widely used by the chemical and automotive industry, in controlling environmental pollution, and in energy conversion technology[1,2,3,4]. Sintering through Ostwald ripening leads to a reduction of the number of exposed metal atoms and is a common deactivation pathway of heterogeneous catalysts[13,14,15]. Several studies attempted to describe SAC stability in terms of the binding energy (Ebind) of a single-metal atom to the support[17,18,19]. All these investigations presume that stronger binding of a metal on a support will make it less prone to sintering. Several reports dealt with diffusion pathways of metal atoms on a support[20,21], the thermodynamic and kinetic aspects of stability of SACs have not been systematically explored yet
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