Structure sensitivity in the nonscalable regime explored via catalysed ethylene hydrogenation on supported platinum nanoclusters

Abstract

The sensitivity, or insensitivity, of catalysed reactions to catalyst structure is a commonly employed fundamental concept. Here we report on the nature of nano-catalysed ethylene hydrogenation, investigated through experiments on size-selected Ptn (n=8–15) clusters soft-landed on magnesia and first-principles simulations, yielding benchmark information about the validity of structure sensitivity/insensitivity at the bottom of the catalyst size range. Both ethylene-hydrogenation-to-ethane and the parallel hydrogenation–dehydrogenation ethylidyne-producing route are considered, uncovering that at the <1 nm size-scale the reaction exhibits characteristics consistent with structure sensitivity, in contrast to structure insensitivity found for larger particles. The onset of catalysed hydrogenation occurs for Ptn (n≥10) clusters at T>150 K, with maximum room temperature reactivity observed for Pt13. Structure insensitivity, inherent for specific cluster sizes, is induced in the more active Pt13 by a temperature increase up to 400 K leading to ethylidyne formation. Control of sub-nanometre particle size may be used for tuning catalysed hydrogenation activity and selectivity.

Surface‐supported cluster catalysis: Ensembles of metastable states run the show

“…In this case, one additional Pt atom is a game‐changer and significantly decreases the activity of the Pt cluster toward dehydrogenation reaction. Furthermore, it has been shown that each of MgO‐supported Pt n clusters ( n = 8–15) has their own unique properties for ethylene hydrogenation, which cannot be extrapolated from the larger scale region . This is, in fact, in stark contrast to what has been observed for bulk platinum.…”

“…This is, in fact, in stark contrast to what has been observed for bulk platinum. Different crystal planes of platinum show the same turnover frequency for hydrogenation reactions, which makes the reaction insensitive to the structure of bulk platinum . Moreover, it has been shown that Pt clusters dispersed on SnO/Al 2 O 3 can be up to 100 times more active than the conventional Pt or V catalysts used for oxidative dehydrogenation of propane .…”

Recent Advanced Materials for Electrochemical and Photoelectrochemical Synthesis of Ammonia from Dinitrogen: One Step Closer to a Sustainable Energy Future

“…Sub‐Nanometer Materials : As the particle size further decreases to sub‐nanometer (sub‐nano) regime (diameter <1 nm), materials are now at molecular level or single‐unit cell level with unique physical and chemical properties that cannot be simply extrapolated from size‐related scaling relations of their particle counterparts with larger sizes . This phenomenon is known as the quantum effect .…”

“…This phenomenon is known as the quantum effect . Another intriguing feature of sub‐nanomaterials is that their fraction of exposed atoms to total number of atoms, known as the “fraction of exposed atoms” or “degree of dispersion,” is approaching unity . Such highly exposed atoms not only enhance their catalytic activity but also magnify the atomic utilization efficiency; thus, making sub‐nanocatalysts appealing to researchers' attention .…”

“…Another intriguing feature of sub‐nanomaterials is that their fraction of exposed atoms to total number of atoms, known as the “fraction of exposed atoms” or “degree of dispersion,” is approaching unity . Such highly exposed atoms not only enhance their catalytic activity but also magnify the atomic utilization efficiency; thus, making sub‐nanocatalysts appealing to researchers' attention . For example, Shi et al reported that Au sub‐nanoclusters (≈0.5 nm, Figure 6 a) embedded on TiO 2 demonstrated a high NH 3 yield rate of 21.4 µg mg −1 cat h −1 and an 8.11% FE at −0.2 V versus RHE.…”