Sulfur Moiety as a Double-Edged Sword for Realizing Ultrafine Supported Metal Nanoclusters with a Cationic Nature

Abstract

Heterogeneously and uniformly dispersed metal nanoclusters with high thermal stability and stable nonmetallic nature show outstanding catalytic performance. In this work, we report on the role of sulfur moieties in hydrochlorination catalysis over carbon-supported gold (Au/C). A combination of experimental and theoretical analyses shows that the −SO3H and derived −SO2H sulfur species in high oxidation states at the interface between Au and −SO3H at ≥180 °C give rise to high thermal stability and catalytic activity. By contrast, the grafted thiol group (−SH) and the derived low-valence sulfur species on carbon markedly destabilize the Au nanoclusters, promoting their rapid sintering into large Au nanoparticles and leading to the loss of their cationic nature. Theoretical calculations suggest that −SO3H favorably adsorbs and stabilizes cationic Au species. Compared to Au/C and Au–SH/C with the Auα+/Au0 atomic ratios of 1.02 and 0.24, respectively (α = 1 or 3), the activity and durability of acetylene hydrochlorination are remarkably enhanced by the interaction between the −SO3H moieties and cationic Au species that enables the high oxidation state of Au to be effectively retained (Auα+/Au0 = 3.82). These results clearly demonstrate the double-edged sword effect of sulfur moieties on the catalytic Au component in acetylene hydrochlorination. The double-edged sword effect of sulfur species in the stabilization/destabilization of metal nanoclusters is also applicable to other metals such as Ru, Pd, Pt, and Cu. Overall, this study enriches the general understanding of the stabilization of metal clusters and provides insight into a wet chemistry strategy for stabilizing supported ligand-free nanoclusters.

Acetylene hydrochlorination over supported ionic liquid phase (SILP) gold-based catalyst: Stabilization of cationic Au species via chemical activation of hydrogen chloride and corresponding mechanisms

“…Au-N(CN)2/AC showed two Au states characterized by Au 4f7/2 binding energies (BEs) of 86.7-86.9 and 85.1-85.5 eV [68,69], which can be attributed to the high-valent Au(III) and Au(I) species, respectively (Figure 1e). Furthermore, the peaks at 84.0-84.2 eV [70,71] were assigned as the metallic Au(0) in Au-Cl/AC ( Figure S7b), which was in accord with our previous work [18,62]. The XPS data were consistent with the HAADF-STEM micrographs of Au-N(CN)2/AC ( Figure 1d) and Au-Cl/AC ( Figure S7a).…”

Octahedral gold-silver nanoframes with rich crystalline defects for efficient methanol oxidation manifesting a CO-promoting effect

“…We also note that not only the Au defects but also the Ag atoms on Au 3 Ag NFs might conjunctively facilitate the OH − adsorption. Moreover, the positively polarized Au δ+ sites have been reportedly shown enhanced Au oxidation activities 68 . As a synergy of all the above factors, the electrokinetics of MOR is greatly enhanced through the mediation of intermediate binding and corresponding activation barriers.…”

Pyrrolidone ligand improved Cu‐based catalysts with high performance for acetylene hydrochlorination

“…From previous studies, excessive activation of C 2 H 2 would facilitate the carbon deposition, [ 25 ] which might be the main reason for the catalyst deactivation. Furthermore, a high electron density of Cu could help to activate the CC bond and increase the activity of C 2 H 2 dimerization, [ 26,27 ] which is exactly what we do not want to happen. Thus, how to weaken the activation of C 2 H 2 and decrease the electron density of Cu are worthy to ponder over.…”

“…[29][30][31] The metal-O structure was also proved to be beneficial for this reaction. [26] In view of the abovementioned facts, several cheap pyrrolidone ligands containing N and O atoms were chosen, and because of the larger electronegativity of O, it is easier to form coordination structure with Cu. A series of Cu(I) complex catalysts supported on SAC were prepared by an incipient wetness impregnation and then used in acetylene hydrochlorination reaction to evaluate the catalytic activity and stability in this paper.…”