Ligand-engineered copper nanoclusters may aid in fight against CO2 emissions

Though often overshadowed by gold and silver, copper (Cu) emerges as a powerhouse in transformative research thanks to its exceptional versatility. A joint initiative by researchers from Tohoku University, the Tokyo University of Science, and the University of Adelaide has introduced an innovative approach to improve the selectivity and sustainability of electrochemical CO₂ reduction processes.

By meticulously engineering the surfaces of Cu nanoclusters (NCs) at the atomic level, this dedicated team has opened the door to innovative and eco-friendly carbon conversion technologies. This advancement demonstrates the transformative capabilities of Cu in sustainable chemistry and also underscores the vital role of global collaboration in tackling urgent issues such as carbon emissions.

Electrochemical CO₂ reduction reactions (CO₂RR) have received considerable attention in recent years because of their potential to convert excess CO₂ from the atmosphere into valuable products. Among the various studied nanocatalysts, NCs have emerged as significant contenders due to their unique advantages over larger nanoparticles.

Within this category, Cu NCs have demonstrated considerable promise, providing the capability to form diverse products, high catalytic efficiency, and sustainability. Despite these advantages, achieving precise control over product selectivity at an industrial scale remains a challenge. As a result, current research is intensely focused on refining these properties to unlock the full potential of Cu NCs for sustainable CO₂ conversion.

“To achieve this breakthrough, our team had to modify NCs at the atomic scale,” explains Professor Yuichi Negishi of Tohoku University, “However, it’s very challenging since the geometry of the NCs was heavily dependent on the precise parts that we needed to alter. It was like trying to move a supporting pillar of a building.”

The researchers successfully created two Cu₁₄ nanoclusters (NCs) with the same structural designs by changing the thiolate ligands (PET: 2-phenylethanethiolate; CHT: cyclohexanethiolate) on their surfaces.

To address this challenge, a meticulously controlled reduction approach was developed, allowing for the synthesis of two structurally identical NCs featuring different ligands—a noteworthy advancement in NC design. Nonetheless, the team noted differences in the stability of these NCs, which stem from variations in intercluster interactions. Such differences are pivotal in determining the durability of these NCs during catalytic processes.

Despite the near-identical geometries resulting from two distinct thiolate ligands, they exhibited significantly different product selectivity in testing their catalytic performance for CO₂ reduction. These differences ultimately affect the overall efficiency and selectivity of the CO₂ reduction reaction (CO₂RR).

“These findings are pivotal for advancing the design of Cu NCs that combine stability with high selectivity, paving the way for more efficient and reliable electrochemical CO₂ reduction technologies,” Negishi concludes.

Journal reference:

1. Yamato Shingyouchi, Masaki Ogami, Sourav Biswas, Tomoya Tanaka, Maho Kamiyama, Kaoru Ikeda, Sakiat Hossain, Yusuke Yoshigoe, D. J. Osborn, Gregory F. Metha, Tokuhisa Kawawaki, Yuichi Negishi. Ligand-Dependent Intracluster Interactions in Electrochemical CO2 Reduction Using Cu14 Nanoclusters. Small, 2024; DOI: 10.1002/smll.202409910