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NOTICE This document contains information of a preliminary nature. It is subject to revision or correction and therefore does not represent a final report.

Decomposition of a fuel-soluble precursor was used for in situ generation of Pd/PdO nanoparticles, which then catalyzed ignition of the methane/O2/N2 flow. To help understand the relationship between particle properties and activity, the composition, structure, and surface chemical state of the particles were determined by a combination of high-resolution transmission electron microscopy (HRTEM), electron diffraction, scanning transmission electron microscopy/energy dispersive X-ray spectroscopy (STEM/EDX), and X-ray photoelectron spectroscopy (XPS). The particles, collected under methane-free conditions, were found to be primarily crystalline, metallic Pd, with TEM results showing a narrow size distribution around 8 nm and scanning mobility particle sizing measurements (SMPS) indicating a median particle size of ∼10 nm. The ignition temperature was lowered ∼150 K by the catalyst, and we present evidence that ignition is correlated with formation of a subnanometer oxidized Pd surface layer.