Operando X-ray photoelectron spectroscopy cell for water electrolysis: A complete picture of iridium electronic structure during oxygen evolution reaction

Operando investigations are crucial for understanding various catalytical processes. We present a newly designed cell for operando X-ray Photoelectron Spectroscopy water electrolysis. All measurements are done on a laboratory X-ray source, which makes the cell easily accessible to a wide audience. We demonstrate the cell operation on a magnetron -sputtered iridium catalyst for the anode of a Proton Exchange Membrane Water Electrolyzer. The main challenges consist of the anode water intake through the membrane from the cathode and the electrical contact. We can oxidize metallic Ir0 into a stable IrIV and reduce it back to metal, which agrees well with the exsitu measurements. Furthermore, the operando tracking of the Ir 4f and O 1s spectra during the oxidation uncovers the presence of intermediates of the Oxygen Evolution Reaction on Ir, and thus allows the improvement of the understanding of its mechanism. The cell can be used to further study other catalysts for low -temperature water electrolyzers, both noble and non -noble metal -based.