Understanding Copper's Role in Turning CO₂ into Useful Products
 

Researchers from the Interface Science Department (ISC) of the Fritz Haber Institute and the University of California Los Angeles (UCLA) have provided insight into the significant morphological changes that Cu surfaces undergo during the electrochemical reduction of CO₂, which influences the type of products formed. This combined theory (UCLA)-experimental ISC-FHI) study highlights the importance of specific surface defects, that are created and transformed in the course of the reaction, for enhancing the efficiency of CO₂ conversion into industrially valuable chemicals.

Key Aspects

• Copper's surface structure is crucial for effective CO₂ reduction.
• Defects and steps on copper surfaces enhance product selectivity.
• Copper surfaces self-restructure under reaction conditions.
• Understanding these changes can improve CO₂ conversion technologies.

Introduction

The electrochemical reduction of carbon dioxide (CO₂) is a promising method to convert this greenhouse gas into useful chemicals. Copper (Cu) stands out as a key material for this process, but its effectiveness depends heavily on its surface structure. Complexity is added to the problem by the fact that the active Cu surfaces are highly dynamic and experience drastic transformations under catalytic working conditions.

The Role of Copper Surfaces

Copper's ability to convert CO₂ into multi-carbon products, like ethylene and ethanol, is influenced by the presence of defects and steps on its surface. These imperfections provide active sites that facilitate the reaction, leading to a higher yield of the desired products. Experimental results indicate that copper surfaces undergo restructuring under CO₂ reduction conditions, although capturing detailed atomic structures remains challenging. Thus, mechanistic understanding of structure-reactivity correlations requires a close collaboration with theorists, as exemplified in this joint UCLA-FHI contribution led by Prof. Philippe Sautet and Prof. Anastassia Alexandrova (UCLA) and Dr. Markus Heyde and Prof. Beatriz Roldán Cuenya (FHI).

Surface Restructuring

During the CO₂ reduction process, copper surfaces undergo significant restructuring. This transformation is driven by the reaction conditions and the strong binding of reaction intermediates, such as carbon monoxide (CO), to the surface. The restructuring enhances the surface's activity and selectivity for producing hydrocarbons and fuels. Theoretical models using advanced calculations have shown that planar copper surfaces are less active, while steps and kinks are crucial for CO₂ reduction.

Implications for CO₂ Conversion

Understanding how copper surfaces change during CO₂ reduction can lead to more efficient and selective conversion processes. By optimizing the surface structure, researchers can improve the production of specific chemicals, contributing to more sustainable and economically viable CO₂ utilization technologies.

This research provides valuable insights into the atomic-level processes that govern CO₂ reduction on copper, paving the way for advancements in the field of sustainable chemistry.