Uniformity Is Key in Defining Structure–Function Relationships for Atomically Dispersed Metal Catalysts: The Case of Pt/CeO₂

Abstract

Catalysts consisting of atomically dispersed Pt (Ptiso) species on CeO2 supports have received recent interest due to their potential for efficient metal utilization in catalytic convertors. However, discrepancies exist between the behavior (reducibility, interaction strength with adsorbates) of high surface area Ptiso/CeO2 systems and of well-defined surface science and computational model systems, suggesting differences in Pt local coordination in the two classes of materials. Here, we reconcile these differences by demonstrating that high surface area Ptiso/CeO2 synthesized at low Pt loadings (<0.1% weight) exhibit resistance to reduction and sintering up to 500 °C in 0.05 bar H2 and minimal interactions with COproperties previously seen only for model system studies. Alternatively, Pt loadings >0.1 weight % produce a distribution of sub-nanometer Pt structures, which are difficult to distinguish using common characterization techniques, and exhibit strong interactions with CO and weak resistance to sintering, even in 0.05 bar H2 at 50 °Cproperties previously seen for high surface area materials. This work demonstrates that low metal loadings can be used to selectively populate the most thermodynamically stable adsorption sites on high surface area supports with atomically dispersed metals. Further, the site uniformity afforded by this synthetic approach is critical for the development of relationships between atomic scale local coordination and functional properties. Comparisons to recent studies of Ptiso/TiO2 suggest a general compromise between the stability of atomically dispersed metal catalysts and their ability to interact with and activate molecular species.

One-Step High-Temperature-Synthesized Single-Atom Platinum Catalyst for Efficient Selective Hydrogenation

“…The stability of SACs is a critical issue for their practical applications [15][16][17]. It was reported that the presence of subnanometer clusters in SACs can affect the overall thermal stability [18][19][20][21][22][23]. Tremendous efforts are made to improve the thermal stability by enhancing the metal-support interactions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

First-principles insight into CO hindered agglomeration of Rh and Pt single atoms on m-ZrO2

“…3,12,18,19 Even similar SAs on the same oxide support may exhibit distinct reactivity. [20][21][22] A major obstacle for the use of SAs in heterogeneous processes is their instability at reaction conditions. SAs have a tendency to agglomerate to form larger particles at the expense of SA and small clusters, change sites, 23 and the catalyst may become deactivated in the process.…”

Synthetic strategies of supported atomic clusters for heterogeneous catalysis

“…By choosing a cationic precursor (always coordinated by four ammine molecules), the Coulombic attraction between the surface O − and the precursor promotes the deposition. Using this SEA method, they prepared Pt 1 /CeO 2 99 , Pt 1 /TiO 2 100 , and Rh-ReO x /Al 2 O 3 101 atomically dispersed catalysts.…”