Breakthrough study unveils key steps for turning CO2 into valuable chemicals

CO₂ Reduction: A Pathway to Valuable Chemicals

The electrochemical reduction of CO₂ (CO₂RR) is a promising technology that uses renewable electricity to convert CO₂ into high-value chemicals, effectively closing the carbon cycle. Ethylene and ethanol, the focus of this study, are crucial for producing environmentally-friendly plastics and fuels, respectively. However, the exact mechanisms and intermediate steps involved in this conversion have remained elusive until now. The former mechanistic understanding is crucial in order to rationally design the active sites, which we show here are not only present in the synthesized pre-catalyst, but can also be formed and evolve in the course of the reaction through the interaction with reactants and reaction intermediates.

Key Findings: Spectroscopic Insights and Theoretical Support

The research team led by group leader Dr. Arno Bergmann, Prof. Dr. Beatriz Roldán Cuenya and Prof. Dr. Núria López employed in-situ surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) to investigate the molecular species on copper (Cu) electrocatalysts and thereby, gain insights into the reaction mechanism. Their findings reveal that the formation of ethylene occurs when specific intermediates, known as *OC-CO(H) dimers, form on undercoordinated Cu sites. Conversely, the production of ethanol requires highly compressed and distorted coordination environment of the Cu sites, with the key intermediate *OCHCH₂.

Understanding the Role of Surface Morphology

One of the critical discoveries is the role of surface morphology in the reaction process. The team found that the undercoordinated Cu sites strengthen the binding of CO, a crucial step in the reduction process. These Cu sites, characterized by atomic-level irregularities, likely form under reaction conditions and make the catalytic surface more effective, leading to better performance in producing ethylene and ethanol.

These findings have significant implications for the chemical industry, particularly in the production of plastics and fuels. By understanding the specific conditions and intermediates required for the selective production of ethylene and ethanol, researchers can design more efficient and sustainable catalysts. This could lead to more effective ways to utilize CO₂, reducing the carbon footprint of chemical manufacturing processes.

The study was a collaborative effort, with theoretical support from a research group in Spain. This partnership allowed for a comprehensive investigation, combining experimental and theoretical approaches to provide a detailed understanding of the CO₂ reduction process.

The research conducted by the Interface Science Department at the Fritz Haber Institute and Institute of Chemical Research of Catalonia represents a significant step forward in the field of CO₂ reduction. By unveiling the key intermediates and active sites involved in the production of ethylene and ethanol, this study provides a foundation for developing more efficient and sustainable catalytic processes. The findings not only advance scientific knowledge but also offer practical solutions for reducing CO₂ emissions and promoting sustainable chemical production.