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.