Interstitial and substitutional light elements in transition metals for heterogeneous catalysis

Abstract

TOC summarises some recent developments in synthesis, characterisation and catalytic applications of light elements doped to transition metals presented in this article.

Intercalating lithium into the lattice of silver nanoparticles boosts catalytic hydrogenation of carbon–oxygen bonds

“…Our previous work has detailed a method for the synthesis of a stable interstitial species such as smaller Li, B and C elements into the Pd lattice after reduction at elevated temperature, which causes detectable Pd lattice expansion due to electron enrichment in Pd. 53–56 In contrast, we did not see significant change in the Ag lattice upon Li + doping, even after reduction at the same temperature, presumably due to the poor catalytic properties of Ag (see Fig. S7 and S8 and Table S2; ESI † ).…”

“… 65 Our future work will explore further the structure and activity relationships of a wide range of interstitial ions or atoms in transition metal lattices combined with atomic scale spectroscopic techniques to see their catalytic impacts on chemical conversions. 53 …”

“…We have recently summarized the “d-band theory” on metal NPs modified by interstitial or substitutional elements. 53 In this article, work of Nørskov et al who conducted pioneering research to rationalize the resulting catalytic effect of mono metallic NPs during selective hydrogenation by conducting DFT calculations is particularly highlighted. They identified that the absorption energies of organic molecules can be varied depending on the degree of substitution and lattice parameters of the doped element(s).…”

Direct Visualization of Substitutional Li Doping in Supported Pt Nanoparticles and Their Ultra‐selective Catalytic Hydrogenation Performance

“…Instead of blocking the interstitial sites from hydrogen accommodation and the resulting excessive hydrogenation, as is the case for the palladium system Pd− int Li, the catalytic activity and selectivity of Pt metal NPs may also be altered by the position of the d‐band centroid of the metallic structure, , and the degree of electron filling with respect to the Fermi level. The downshift of the d‐band centroid will decrease the adsorbate‐substrate binding strength, whereas the degree of electron filling will also reduce the binding energy [25] . Substitutional Li doping results in only a small change in the lattice parameter, hence the effect of d‐band down‐shifting is weak [26] .…”

“…The downshift of the dband centroid will decrease the adsorbate-substrate binding strength, whereas the degree of electron filling will also reduce the binding energy. [25] Substitutional Li doping results in only a small change in the lattice parameter, hence the effect of dband down-shifting is weak. [26] In addition, lithium is a highly electropositive element that does not have available p or d orbitals for hybridizations with the host framework atoms which alter the Pt d-band position (in contrast to other light element dopants such as boron and carbon).…”