Outstanding Methane Oxidation Performance of Palladium‐Embedded Ceria Catalysts Prepared by a One‐Step Dry Ball‐Milling Method

Abstract

By carefully mixing Pd metal nanoparticles with CeO 2 polycrystalline powder under dry conditions,a nu npredicted arrangement of the Pd-O-Ce interface is obtained in which an amorphous shell containing palladium species dissolved in ceria is covering ac ore of CeO 2 particles.T he robust contact that is generated at the nanoscale,a long with mechanical forces generated during mixing, promotes the redox exchange between Pd and CeO 2 and creates highly reactive and stable sites constituted by PdO x embedded into CeO 2 surface layers.T his specific arrangement outperforms conventional Pd/CeO 2 reference catalysts in methane oxidation by lowering light-off temperature by more than 508 8Ca nd boosting the reaction rate.The origin of the outstanding activity is traced to the structural properties of the interface,modified at the nanoscale by mechanochemical interaction.

Low-Temperature Methane Partial Oxidation over Pd Supported on CeO2: Effect of the Preparation Method and Precursors

“…The Pd 3d spectra of the samples prepared by impregnation showed exactly the same pattern, independently of the Pd precursor used (Figure 3c,d). The Pd 3d 5/2 spectra contain two bands at about 336.4 and 338.0 eV, which correspond well to Pd 2+ and Pd 4+ species, respectively [21,24]. The surface atomic ratio Pd 4+ /(Pd 4+ +Pd 2+ ) in these samples prepared by impregnation is about 0.2.…”

“…Recent density functional theory (DFT) calculations have shown that Pd x Ce 1−x O δ surfaces are particularly effective in the activation of the C-H bonds in the methane molecule [33,35], and that substitution of Ce by Pd ions originates highly active and stable systems [36,37]. The mechanochemical forces that operate in the ball milling preparation method would enhance the formation of such active surfaces and substituted structures, as demonstrated recently in the total oxidation of methane [21]. In fact, the amorphous shell observed in the HRTEM images of the Pd/CeO 2 catalyst prepared by ball milling ceria and Pd acetate (Figure 1) is expected to be particularly active due to undercoordinated sites, as claimed recently by DFT calculations for the activation of methane [38].…”

“…As commonly occurs in catalysis, the intricate properties of the metal-support interaction depend on the method used for the preparation of the catalyst. In recent years, it has been demonstrated that different architectures of the Pd-CeO 2 interface are obtained by using conventional impregnation or solution combustion synthesis or mechanochemical methods, which strongly determine the performance of the resulting Pd/CeO 2 catalysts in the total oxidation of methane [20][21][22][23]. In particular, advanced operando characterization has recently shown that catalysts prepared by mechanical milling are clearly superior because they contain very stable palladium species [24].…”

Sustainable synthesis of supported metal nanocatalysts for electrochemical hydrogen evolution

“…In addition to the synthesis of carbon-supported metal NPs, the ball milling method is useful for the synthesis of metal oxide-loaded metal NPs. As a representative example, Trovarelli et al [78] developed a controlled ball milling procedure to produce a Pd/CeO2 nanocomposite using Pd NPs (less than 2 nm in size) as precursors instead of the common metal precursor (Table 1). Notably, a unique Pd-O-Ce interface was achieved under ball milling, due to the uniform coverage of Pd NPs on the CeO2 surface.…”

Mechanochemie gasförmiger Reaktanten

“…hergestellten heterogenen Katalysatoren entsprechen, eingesetzt. [25] In vielen Fällen erwies sich Kugelmahlen als essentiell füre ine Verbesserung der Oberfläche eines festen Katalysators, [26] der Optimierung des katalytischen und des Redoxverhaltens, [27] der Erhçhung der Dispersion auf der Katalysatormatrixoberfläche, [28] die Steigerung der Mesoporositätd es Festkçrpers und die Milderung der thermischen Bedingungen, die der heterogene Katalysator zur Funktion bençtigt. [29,26] Obwohl die Mehrheit der mechanisch synthetisierten Katalysatoren in Experimenten mit kontrollierten Mikroreaktoren, wie Festbettreaktoren, [24] [31] Im Jahr 2011 verçffentlichten Mulas et al eine mechanochemische Hydrierung von Kohlenmonoxid an mechanochemisch dargestellten heterogenen Katalysatoren [Gl.…”