Descriptor of catalytic activity nanoparticles surface: Atomic and molecular hydrogen on gold

Hydrogen diffusion on (100), (111), (110) and (211) gold faces

“…For the p-band centers no correlation with the diffusion barrier values is observed as the p-orbitals of the gold atoms are valence orbitals. Similar trends were previously observed in the study of H adsorption on Au atoms [9].…”

“…Reducing the number of step edges or low-coordinated atoms will facilitate the H migration but at the same time will reduce the reactivity [9]. Diffusion of molecular hydrogen on gold was not considered due to the rather high activity of low-coordinated Au sites in the H 2 dissociation reaction [9]. The supplied molecular hydrogen will rapidly dissociate on active sites of the peripheral parts of the nanoparticle/substrate contact [39][40][41] or on various NP surface defects [9,42].…”

“…Diffusion of molecular hydrogen on gold was not considered due to the rather high activity of low-coordinated Au sites in the H 2 dissociation reaction [9]. The supplied molecular hydrogen will rapidly dissociate on active sites of the peripheral parts of the nanoparticle/substrate contact [39][40][41] or on various NP surface defects [9,42]. In particular, the activity of gold NPs is sufficient for the H 2 dissociation at room temperature, which is confirmed experimentally [43].…”

“…To simplify the activity estimates, some researchers have switched to working with various activity descriptors directly related to the free energy of the reaction under study [1-3], the adsorption energies of reagents and intermediates [4], and so forth. In the framework of heterogeneous catalysis, the descriptors are the parameters of the catalyst electronic structure and, as a rule, these are the centers of the d-band [5-8] or other bands [9] involved in the adsorption bond formation.…”

“…To simplify the activity estimates, some researchers have switched to working with various activity descriptors directly related to the free energy of the reaction under study [1-3], the adsorption energies of reagents and intermediates [4], and so forth. In the framework of heterogeneous catalysis, the descriptors are the parameters of the catalyst electronic structure and, as a rule, these are the centers of the d-band [5-8] or other bands [9] involved in the adsorption bond formation.Focusing on the reaction process itself, researchers often tend to neglect such an important factor as diffusion of the reagents [10]. In some cases [10,11], it is the diffusion of reagents or mass transfer to the active centers on the catalyst surface that acts as the rate-limiting step.…”