Catalyst deactivation via decomposition into single atoms and the role of metal loading

Abstract

In the high-temperature environments needed to perform catalytic processes, supported precious metal catalysts severely lose their activity over time. Even brief exposure to high temperatures can lead to significant losses in activity, which forces manufacturers to use large amounts of noble metals to ensure effective catalyst function for a required lifetime. Generally, loss of catalytic activity is attributed to nanoparticle sintering, or processes by which larger particles grow at the expense of smaller ones. Here, by independently controlling particle size and particle loading using colloidal nanocrystals, we reveal the opposite process as a novel deactivation mechanism: nanoparticles rapidly lose activity by high-temperature nanoparticle decomposition into inactive single atoms. This deactivation route is remarkably fast, leading to severe loss of activity in as little as ten minutes. Importantly, this deactivation pathway is strongly dependent on particle density and concentration of support defect sites. A quantitative statistical model explains how for certain reactions, higher particle densities can lead to more stable catalysts.Increased catalyst stability, especially in automotive emissions control applications, is of paramount importance in order to decrease the loading of rare and precious noble metals 1,2 .

Hydrogen migration at restructuring palladium–silver oxide boundaries dramatically enhances reduction rate of silver oxide

“…Prior studies have demonstrated that the interface between metal nanoparticles and the metal oxide support can affect chemical behavior by the creation of specific active sites [12][13][14][15][16][17][18] and direct migration or "spillover" 19 of reactive species created on one phase to a neighboring phase of differing reactivity [19][20][21][22][23][24][25] . The metal/oxide support interface can significantly restructure in reactive gas environments on a short timescale of minutes and long length scales of microns 26 . Catalyst activity can be significantly modified by interface restructuring including changes in coordination environment 27 , catalyst encapsulation 28 , and metal component transport and alloying [29][30][31][32][33] .…”

Study of spatial and temporal aging characteristic of catalyzed diesel particulate filter catalytic performance used for diesel vehicle

“…It can be seen that the crystallinity of the inlet region was highest, followed by the outlet region and the middle region was the smallest. The increase of crystallinity is mainly caused by the sintering of noble metals and metal oxides and the formation of agglomerates with poor crystalline phase 40 .

Figure 11 Crystallinity of the inlet, middle and outlet regions of CDPF after aging.

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Single-atom site catalysts for environmental catalysis

“…Similar to independent catalysis of CO oxidation and NO reduction, both CO and NO could easily be eliminated from gasoline-fueled engine exhaust systems by SACs [58,65,66]. However, the usefulness of SACs and small clusters with ensemble sites catalysts have been the debate for HC (CH4, C3H6 and C3H8) oxidation [56,58,66,128].…”