Copper and silver gas diffusion electrodes performing CO(2)reduction studied throughoperandoX-ray absorption spectroscopy

摘要

X-ray absorption spectroscopy (XAS) offers the unique possibility to study metal electrocatalysts such as silver and copper while they are performing electrochemical carbon dioxide (CO2) reduction. In this work, we present an approach to performoperandoXAS experiments on an electrochemical cell performing CO(2)reduction with a gas diffusion electrode (GDE) as cathode. The experimental set-up, advantages and drawbacks, XAS data analysis, and XAS theory are discussed. Results on copper and silver GDEs obtained through the presented procedures are then presented and discussed. Structural and compositional catalyst data acquired underoperandoconditions can help further density functional theory calculations, and catalytic, and systems studies on CO(2)reduction. Structural and compositional data including crystallite size were obtained while performing high current density (up to 200 mA cm(-2)) CO(2)reduction. On the silver catalysts at higher than 100 mA cm(-2)applied current density, a Ag-X contribution was found and is ascribed to Ag-O. For both silver and copper, the XAS experiments revealed that the crystallite size of theex situsamples is smaller than the samples during CO(2)reduction. Furthermore, metal particle size polydispersity was found in the silver catalysts by comparing the obtained coordination numbers with theoretical values. TheoperandoEXAFS data was of such high quality (k: 3-14 angstrom(-1)) that four shells could be fitted. The value of combiningex situmaterial characterisation and electrocatalyst performance data withoperandoXAS experiments is discussed and found to be of great importance to further CO(2)reduction research.