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 about electronic and geometric structures for 3d transition metals, its application to second- and third-row transition metals is often limited by substantial core-hole lifetime broadenings. For the later transition metals, higher d-electron counts further reduce the electronic structural information content due to weak and absent 1s-to-nd 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 have intrinsically narrower 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 well-defined PdO_xH_y complexes and Pd nanoparticles that are relevant to Pd-based catalysts.