Copper is one of the most commonly studied materials for the electrochemical conversion of carbon dioxide (CO₂) into valuable chemical products. Numerous efforts have been made to enhance the product selectivity - an important characteristic essential for efficient chemical production from CO₂ - of Cu with only marginal progress. Here, we introduce a pulsed-bias technique for the electrochemical reduction of CO₂ on Cu catalyst which led to 100% selectivity for CO formation over other carbon products and only produced syngas (CO + H₂). X-ray photoelectron spectroscopy (XPS) and controlled CO₂ electrochemical reduction experiments suggest that in-situ oxidation and reduction of the Cu causes the preference for CO formation over other carbon products on polycrystalline Cu. Moreover, the observed pulse waveform dependency of the H₂ to CO product ratio can also be beneficial by allowing tunable CO₂ reduction products as a controllable syngas feedstock for different industrial applications (e.g., Fischer-Tropsch process, and hydroformylation of alkenes to aldehydes) without an additional hydrogen source. This study opens a new route for the selective conversion of CO₂ into syngas on robust and cost-effective Cu catalysts, which could be adopted at large scale in the chemical industry. 

Keywords: Copper, Catalyst, CO₂reduction, Syngas, Selectivity, Electrochemistry