Reduction*

Electrocatalytic reduction of carbon dioxide (CO₂) towards value-added chemicals has been identified as a revolutionary technology, which tackles long-term pending issues of “greenhouse” effect and fossil fuel shortage. From the perspective of technological development, monitoring the catalytic process for in-depth dynamic changes is regarded as a significant advance to optimize the catalysts and govern the whole reaction for potential practical utilizations. Herein, we apply synchrotron radiation-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) integrated with online gas detection via mass spectrometry to in situ study solid-liquid interface chemistry at the atomic scale coupled with product measurements during CO₂ reduction, using Cu/Ag based membrane electrode assemblies in a flow cell. We build up a well-defined relationship between the electronic structure of catalytic metal sites and the products under reaction conditions. The carbon-based reaction intermediates are characterized at different cathodic potentials, especially shown as C-O(H) and C-H species. The pivotal role of water is also investigated in the formation/desorption process of key intermediates/products. Our findings will enhance researchers’ comprehension on the catalytic mechanisms of CO₂ reduction.