Carbon Monoxide Promotes the Catalytic Hydrogenation on Metal Cluster Catalysts

Abstract

Size effect plays a crucial role in catalytic hydrogenation. The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom metal catalysts and metal nanoparticles. However, for the unfavorable electronic property and their interaction with the substrates, they usually exhibit sluggish activity. Taking advantage of the small size, their catalytic property would be mediated by surface binding species. The combination of metal cluster coordination chemistry brings new opportunity. CO poisoning is notorious for Pt group metal catalysts as the strong adsorption of CO would block the active centers. In this work, we will demonstrate that CO could serve as a promoter for the catalytic hydrogenation when ultrasmall Pd clusters are employed. By means of DFT calculations, we show that Pdn n=2‐147 clusters display sluggish activity for hydrogenation due to the too strong binding of hydrogen atom and reaction intermediates thereon, whereas introducing CO would reduce the binding energies of vicinal sites, thus enhancing the hydrogenation reaction. Experimentally, supported Pd2CO catalysts are fabricated by depositing preestablished [Pd2(μ-CO)2Cl4]2- clusters on oxides and demonstrated as an outstanding catalyst for the hydrogenation of styrene. The promoting effect of CO is further verified experimentally by removing and reintroducing a proper amount of CO on the Pd cluster catalysts.

Theoretical modeling for interfacial catalysis

“…Experimentally, the presence of CO usually leads to a dramatic drop in the activity for hydrogenation, that is, CO poisoning, while occasionally results in a promotion in selectivity as the unselective sites would be preferentially blocked. Interestingly, our recent work revealed that ultra‐small Pd cluster catalysts with CO coating exhibited excellent hydrogenation activity toward C=C bond, while removal of CO would significantly reduce the activity 89 . Computationally, a set of Pd n clusters with size varying from Pd 2 to Pd 147 were constructed.…”

“…(Reprinted with permission from Ref. 89. Copyright 2020 Ruixuan Qin et al) (g) Surface phase transition introduced by thiolate.…”

“…Interestingly, our recent work revealed that ultrasmall Pd cluster catalysts with CO coating exhibited excellent hydrogenation activity toward C=C bond, while removal of CO would significantly reduce the activity. 89 Computationally, a set of Pd n clusters with size varying from Pd 2 to Pd 147 were constructed. Figure 7(f) plots the calculated binding energies of dissociated H atoms(ΔE 2H ) versus the reciprocal of the size of Pd n clusters, that is, n −1/3 .…”

From double‐atom catalysts to single‐cluster catalysts: A new frontier in heterogeneous catalysis

“…Zheng et al. [ 106 ] studied the adsorption of H on the Pd n (n = 2‐147) clusters and its hydrogenation performance through the DFT theoretical calculation. The strong adsorption of reactants on ultra‐small Pd metal clusters (such as Pd 2 /TiO 2 and Pd 3 /TiO 2 ) inhibited catalytic hydrogenation, while the introduction of CO weakened the binding strength of hydrogen and hydrogenation intermediates, significantly improving hydrogenation activity.…”

The Factors Dictating Properties of Atomically Precise Metal Nanocluster Electrocatalysts

“…Metal nanoparticles (NPs) occupy a crucial position and play significant roles in heterogeneous catalysis. [1][2][3][4][5][6][7][8][9][10] However, it is quite challenging to establish a precise correlation between the catalytic properties and structures of metal nanoparticles because of the complicated composition/structures of metal nanoparticles obtained by conventional synthesis. [5,6,[11][12][13][14] In order to deepen mechanistic understanding of heterogeneous catalysis, much efforts have always been directed at the synthesis of catalysts with atomically precise structures.…”