Investigation of the evolution of Pd-Pt supported on ceria for dry and wet methane oxidation

Abstract

Efficiently treating methane emissions in transportation remains a challenge. Here, we investigate palladium and platinum mono- and bimetallic ceria-supported catalysts synthesized by mechanical milling and by traditional impregnation for methane total oxidation under dry and wet conditions, reproducing those present in the exhaust of natural gas vehicles. By applying a toolkit of in situ synchrotron techniques (X-ray diffraction, X-ray absorption and ambient pressure photoelectron spectroscopies), together with transmission electron microscopy, we show that the synthesis method greatly influences the interaction and structure at the nanoscale. Our results reveal that the components of milled catalysts have a higher ability to transform metallic Pd into Pd oxide species strongly interacting with the support, and achieve a modulated PdO/Pd ratio than traditionally-synthesized catalysts. We demonstrate that the unique structures attained by milling are key for the catalytic activity and correlate with higher methane conversion and longer stability in the wet feed.

Photoelectrochemical N2‐to‐NH3 Fixation with High Efficiency and Rates via Optimized Si‐Based System at Positive Potential versus Li0/+

“…The corresponding Pd 3d spectra in Figure 3b show two Pd 3d 7/2 peaks at ≈335.7 and 336.7 eV characteristic of the Pd-Pd and Pd-O bonds, respectively. [33] Similar to the Cu 2p spectra in Figure 3a, the illumination also caused a downward shift to a lower binding energy of 335.4 eV for the Pd-Pd peak and a slight increase in the ratio of Pd-Pd to Pd-O from 2.89 to 3.18 (Figure 3b). These results indicate the photoinduced charge generation and separation, followed by the electron transport from the nanostructured optical absorber of n + p-Si to the PdCu alloyed nanoparticles.…”

Impact of controlling the crystallinity on bifunctional electrocatalytic performances toward methanol oxidation and oxygen reduction in binary Pd–Cr solid solution

“…The X-ray absorption near edge structure (XANES) of Pd–Cr_ T ( T = 350, 500 and 650 °C) nanofibers were examined at Pd K-edge region (Fig. 2(c)); the absorption energy value and spectral features of Pd–Cr series were identical with those of metallic Pd, 43 implying that Pd in binary Pd–Cr solid solution prevailingly has zero valent oxidation state and same electronic configuration with metallic Pd. The k 3 -weighted Pd K-edge extended X-ray absorption fine structure (EXAFS) spectra shown in Fig.…”

Immobilized Nanomaterials for Environmental Applications

“…Selectivity is still a challenge in these processes as the conversion efficiency largely varies from 30% up to 100% depending on the operational conditions and immobilized catalysts applied ( Table 2 ). Lately, Pd-Pt NPs immobilized on ceria showed remarkable efficiency in completely oxidizing methane under wet conditions, which are relevant for automotive combustion; thus, these scientific findings could be the basis to install a technology to prevent methane emissions from vehicles [ 70 ].…”