A novel electrochemical cell for operando X-ray absorption measurements at low energies: Probing electrochemically induced electronic changes in palladium

Operando assessment of electronic properties near the Fermi level is essential to gain new insights into the mechanisms of electrochemical reactions as well as for the development of more efficient electrocatalysts. However, the high vacuum ambient needed for X-ray absorption measurements at low energies has made studies under electrochemical conditions quite challenging. Here, we describe an out-of-chamber setup with a new electrochemical cell that allowed us to performed operando X-ray absorption studies at the low energy of the Pd L3 edge. Using the new electrochemical cell, we were able to probe, for the first time, the changes in electronic properties of carbon-supported Pd nanoparticles induced by the electrochemical oxidation of the Pd surface. Our results demonstrate that the oxidation process produces an increase in the Pd 4d band vacancy, which indicates that charge is transferred from the metal to the adsorbed oxygenated species.