Evaluating Palladium 4d-to-2p X-ray Emission Spectroscopy for Characterizing Catalytically Relevant Species

X-ray absorption spectroscopy (XAS) has diverse applications in materials characterization and catalysis. While K-edge XAS can provide detailed information on electronic and geometric structure for 3d transition metals, second and third row transition metals suffer from core-hole lifetime broadening of spectral features and, for later transition metals, higher d-electron counts, limiting the electronic structural information due to weak and/or absent 1s-to-3d pre-edge features. L-shell X-ray emission spectroscopy (XES), specifically 4d-to-2p XES can overcome these limitations by accessing transitions that are dipole allowed and that have intrinsically smaller core-hole lifetime broadenings. Herein, the utility of Pd 4d-to-2p XES for in situ catalysis research in both homogeneous and heterogeneous systems is explored through the study of a series of well-defined PdOxHy complexes and Pd nanoparticles that are relevant to Pd catalysts.