From CO<sub>2</sub> to Solid Carbon: Reaction Mechanism,\nActive Species, and Conditioning the Ce-Alloyed GaInSn Catalyst

The electrochemical reduction of CO<sub>2</sub> is a\npromising\nrealization of negative emissions to mitigate climate change, aiming\nat the efficient production and safe long-term storage of carbon-rich\nsink products. This approach, however, necessitates novel catalyst\nmaterials specifically targeting electrochemical carbon dioxide removal.\nIn this work, we investigate synthesis routes for a cerium-incorporated\nGaInSn-based liquid metal catalyst, focusing on the electrochemical\nproduction of graphitic carbon. Preparation and preconditioning of\nthe catalyst are found to be crucial for carbon production, while\ntrace amounts of H<sub>2</sub>O and OH in the organic electrolyte\nplay a decisive role in the efficiency of the electrocatalytic process.\nFinally, for a better understanding of the reaction mechanism and\nthe involved active species, experimental findings and density functional\ntheory-based calculations are combined, suggesting a two-step reduction\npathway with Ce(OH)<sub><i>x</i></sub> as the catalytically\nactive surface species.