In-situ STXM characterization of Cu/Cu₂O electrocatalysts for CO₂ reduction

Scanning Transmission X-ray microscopy (STXM) is a synchrotron-based soft X-ray spectra-microscopic technique which provides chemically selective imaging via spatially resolved X-ray absorption spectroscopy. In-situ STXM of electrocatalysts provides imaging and spectroscopic information at different time / voltage points in the electrochemical process, which helps to understand the changes of morphology and chemistry that occur under reaction conditions. We have developed in-situ flow electrochemical devices with an electrolyte thickness<2 µm which allow STXM measurements while controlling the electrochemical reaction environment, thus providing a platform for in-situ studies of electrochemical oxidation and reduction processes. Here we report results of in-situ STXM studies on electrochemically generated Cu based catalysts for the CO₂ reduction reaction (CO₂R). Cu 2p STXM spectromicroscopy was successfully used to monitor the morphology and oxidation state changes in the initially formed Cu/Cu₂O nano­ particles as the potential was changed from open circuit to values where CO₂ reduction occurs. Ex-situ ptychography was also conducted on the same catalyst nanoparticles to provide spectra-microscopy images with similar chemical analysis but improved spatial resolution.