An optimised Cell for in situ XAS of Gas Diffusion Electrocatalyst Electrodes

The quality of in situ XAS of electrochemical systems is highly sensitive to electrode disturbances, such as gas evolution and gas consumption at an electrolyte/catalyst interface. A novel in situ spectro‐electrochemical X‐ray absorption spectroscopy (SPEC‐XAS) cell is presented as a new tool for the characterisation of gas evolving and consuming electrocatalysts at high overpotentials. By utilising a thin, porous membrane with efficient electrolyte and gas circulating loops, an improved three phase interface is established that enabled efficient gas supply and minimised the interference from bubble formation. X‐ray absorption spectroscopy (XAS) measurements were conducted in fluorescence mode with three experiments selected to demonstrate the cell's performance. The first two reactions; an in‐situ study of a highly active amorphous iridium oxide catalyst during the oxygen evolution reaction (OER) and an in‐situ study of copper oxide during the carbon dioxide reduction reaction (CO2RR) are used to exemplify the XAS data quality achieved under operational conditions. Thirdly, a detailed XAS investigation of a highly dispersed platinum catalyst during the oxygen reduction reaction (ORR) is presented, along with comparative data in nitrogen. These measurements show the retention of oxygen on the surface of the platinum metal particles down to 0.48 V (vs. RHE), well below the platinum oxide reduction peak. Here we present a spectro‐electrochemical cell design for in situ XAS measurements of gas evolving and consuming electrocatalysts. This is exemplified in the study of Iridium oxide for the oxygen evolution reaction and copper oxide for the CO2 reduction reaction. A detailed investigation of platinum during the oxygen reduction is also presented to demonstrate the full scope of the cell.