We report synergistic interaction at the Pd- CeO2 interface leading to rapid catalytic turnover at low temperatures using a mechanically mixed sample in a mini ball mill with 4 %Pd loadings onto a CeO2 support. Its activity was evaluated for the dry reforming of methane (DRM: CH4+CO2 --&gt;2CO + 2H2) where the activation of the C-H bond is the most limiting step. Mechanical mixing of Pd salt nanoparticles with polycrystalline CeO2 powder yielded an active arrangement of the Pd-O-Ce interface highly active for methane DRM. Pd-based formulations were effective in methane activation, while the CeO2 facilitated the dispersion and Pd-Ce interfacial interaction. The catalyst’s structural integrity and chemical state evolution during reaction were probed via in-situ characterization techniques. The remarkable activity for the grinded samples exhibited a high conversion rate, greatly surpassing that of Pd/CeO2 synthesized using the conventional incipient wetness method (Pd/CeO2 IW) on activity tests carried out in a bed-flow reactor setup. These drastic changes were traced to the unique Pd-CeO2 interface that is promoted during milling. The surface chemistry and active intermediates were monitored by in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and diffuse reflectance infrared spectroscopy (DRIFTS). Methane activates on the catalyst surface at temperatures as low as 200 °C. The reaction was closely followed by XRD to examine the structural evolution of the catalyst, while the electronic distribution was probed by XAS measurements. In addition, possible reaction pathways and stable surface intermediates were identified using DRIFTS. A combined in-situ approach was key to understand how Pd-Ce interfacial interactions ultimately play a role in the overall activity and stability of the catalyst.

Interfacial interactions in Pd-embedded ceria catalyst prepared by a one-step dry ball-milling method for methane activation and dry reforming

2019 Fall National Meeting

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