Dynamic surface reconstruction explains how copper sulfide catalysts tune CO₂ reduction

A study published in Materials Advances has revealed how copper sulfide catalysts continuously remodel their surface during electrochemical CO₂ reduction. The research, led by associate professor Akira Yamaguchi from the Institute of Science Tokyo, Japan, used a technique called potential-step electrolysis to monitor the catalyst's transformation.

This method involves repeatedly applying negative and positive electrical potentials to the catalyst, which prompts the formation and reduction of copper and oxygen-containing species. As a result, sulfur atoms leave the surface when a negative potential is applied, generating metallic copper active sites that facilitate CO₂ conversion.

Conversely, a positive potential leads to the formation of copper(I) oxide, which is subsequently reduced back to copper when the potential is switched back to negative. This dynamic surface reconstruction, which contrasts with the conventional assumption of static catalyst surfaces, plays a crucial role in determining product selectivity.

The study found that sulfur on the catalyst surface promotes hydrogen adsorption, while sulfur within the catalyst stabilizes key carbon monoxide intermediates, both of which contribute to formic acid formation. Meanwhile, oxygen incorporated into the catalyst during the positive-potential phase generates copper sites that promote C–C bond formation, shifting selectivity toward multi-carbon products.

The findings provide mechanistic insights into the design of more efficient CO₂ conversion technologies, highlighting the importance of surface transformations in tailoring catalytic activity and selectivity.