Highly Dispersed Pd Species Supported on CeO2 Catalyst for Lean Methane Combustion: The Effect of the Occurrence State of Surface Pd Species on the Catalytic Activity

Abstract

The correlation between the occurrence state of surface Pd species of Pd/CeO2 for lean CH4 combustion is investigated. Herein, by using a reduction-deposition method, we have synthesized a highly active 0.5% PdO/CeO2-RE catalyst, in which the Pd nanoparticles are evenly dispersed on the CeO2 nanorods CeO2-R. Based on comprehensive characterization, we have revealed that the uniformly dispersed Pd nanoparticles with a particle size distribution of 2.3 ± 0.6 nm are responsible for the generation of PdO and PdxCe1−xO2−δ phase with –Pd2+–O2−–Ce4+– linkage, which can easily provide oxygen vacancies and facilitate the transfer of reactive oxygen species between the CeO2-R and Pd species. As a consequence, the remarkable catalytic activity of 0.5% Pd/CeO2-RE is related to the high concentration of PdO species on the surface of the catalyst and the synergistic interaction between the Pd species and the CeO2 nanorod.

Synergistic effects of Au and PdOx on the solar-assisted catalytic ozonation of VOCs

“…The H 2 -TPR curve of PdO 2 –CeO 2 could be divided into two reduction peaks at 82.3 °C and 121.3 °C, corresponding with the reduction of PdO 2 and Pd–O–Ce, respectively. 44 The H 2 -TPR curve of PdO x –Au–CeO 2 had three reduction peaks at 90.4 °C, 117.4 °C, and 138.7 °C, corresponding with the reduction of PdO x , Pd–O–Ce, and Au–O–Ce, respectively. The coloading of Au and PdO x made the reduction peaks of Pd–O–Ce and Au–O–Ce shift to lower temperatures, suggesting a strong interaction between Au and PdO x on CeO 2 surface.…”

Preparation and Performance of Carbon-Based Ce-Mn Catalysts for Efficient Degradation of Acetone at Low Temperatures

“…A higher proportion of Mn 4+ is more conducive to the oxidation of organic matter [ 51 ]. For the XPS maps of Ce 3d ( Figure 4 b), the Ce 3d spectrum can be broken down to eight peaks according to relevant literature [ 25 , 36 , 52 , 53 , 54 , 55 ], including four pairs of spin-splitting primes of Ce 3d that are marked as v and u. Among them, v, v 1 , v 2 , and v 3 are the spin orbits of Ce 3d 5/2, and u, u 1 , u 2 , and u 3 are the spin orbits of Ce 3d 3/2.…”

“…Therefore, higher cerium content is conducive to the formation of more oxygen vacancies on the catalyst surface, and better helps to increase the oxygen transfer rate in the later catalytic degradation of acetone [ 51 , 58 ]. For the XPS maps of O 1s ( Figure 4 c), the fitted peaks with a binding energy of 531.8 and 533.7 eV correspond to lattice oxygen (O α ) and adsorption oxygen (O β ), respectively [ 47 , 53 , 59 ]. As the Ce increased, the numbers of both adsorption oxygen and lattice oxygen on the catalyst surface, as well as the proportion of lattice oxygen, increased.…”

Water inhibition and role of palladium adatoms on Pd/Al2O3 catalysts during methane oxidation

“…Based on activity measurements of catalysts containing high-BE palladium species (attributed to palladium (IV) oxide), Gao et al [61] reported that palladium (IV) oxide is less active than PdO in the oxidation of methane. In contrast, Khader et al [46] and Liu et al [62] attributed the high catalytic activity of their Pd/CeO 2 catalysts to the presence of such high-BE palladium, stabilized by the interaction with the ceria support. These differences may indicate that the support plays a fundamental role in the reactivity of high-BE palladium species, with ceria being more efficient than alumina.…”