Statistical Physics of Coadsorption Isotherms and Rate Processes on Bimetallic Alloys
Full article
| Journal |
Journal of Catalysis
ISSN: 0021-9517
, E-ISSN: 1090-2694
|
| Output data |
Year: 2025,
Volume: 453,
Article number
: 116496,
Pages count
: 13
DOI:
10.1016/j.jcat.2025.116496
|
| Tags |
Adsorption; Catalytic reactions; Bimetallic alloys; Kinetic models; Statistical aspects; Ammonia synthesis |
| Authors |
Zhdanov Vladimir P.
1
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis, Russian Academy of Sciences, Novosibirsk 630090, Russia
|
|
Funding (1)
|
1
|
Ministry of Science and Higher Education of the Russian Federation
|
FWUR-2024-0032
|
Metallic alloys are widely used as catalysts in chemical industry. The understanding of the kinetics of the corresponding elementary reaction steps is, however, still limited due to complex statistical aspects including the diversity of adsorption sites with the same structure but different composition of metal atoms. Herein, using the prescriptions of statistical physics, I derive general equations for describing isotherms of coadsorption on the three- and four-fold hollow sites of the binary-alloy surfaces and related rate processes including monomolecular adsorption and desorption, dissociative adsorption and associative desorption, and Langmuir–Hinshelwood and Eley-Rideal reactions. The rates of these steps are expressed via the probabilities of the formation of adsorption sites with participation of certain numbers of metal atoms of different types. The way how lateral adsorbate–adsorbate interactions can be taken into account is described as well. The general equations are applicable for arbitrary distributions of metal atoms and adsorbate–adsorbate interactions. In numerical calculations illustrating the specifics of coadsorption isotherms and rate processes, the correlations in this distribution are neglected and the adsorbate–adsorbate interactions are neglected as well. With the realistic values of the difference of the adsorbate interaction with metal atoms of different types, the distribution of coadsorbed species over sites is shown to be far from random. The dependence of the rates of various processes on adsorbate coverages is, however, often monotonic but can be nonmonotonic provided the distribution of adsorption sites over binding energy is wide and the interval of variation of coverage is appreciable. Overall, the formalism presented allows one to scrutinize various specific aspects of coadsorption on metal alloys. As explained in detail, it can be employed to clarify the kinetics of a series of practically important catalytic reactions with relatively simple mechanisms such as the ammonia synthesis.