原子レベルの制御で新たな銅ナノクラスターを開発 ― CO₂変換反応の選択的制御が可能なことを実証 ―

2026-07-06 東北大学

図1. 銅ナノクラスターの構造とCO₂電解還元特性の概要。従来のCu₅₀ナノクラスターでは主にギ酸（HCOO⁻）が生成されるのに対し、硫化物イオンを内包したS@Cu₅₀ナノクラスターではメタノール（CH₃OH）生成が促進される。水素原子は見やすさのため省略した。

＜関連情報＞

• https://www.tohoku.ac.jp/japanese/2026/07/press20260706-01-co2.html
• https://pubs.acs.org/doi/10.1021/jacsau.6c00817

原子レベルの価数状態エンジニアリングにより、銅ナノクラスター上でのCO2電気還元反応の方向転換が可能になる Atomic-Level Valence-State Engineering Redirects CO2 Electroreduction on Cu Nanoclusters

Qilin Li,Mandira Ghosh,Mohd Rashid,Rupa Sarma,Pradip Kumar Mondal,Tokuhisa Kawawaki,Sourav Biswas,Biswarup Pathak,and Yuichi Negishi
JACS Au  Published: June 30, 2026
DOI:https://doi.org/10.1021/jacsau.6c00817

Abstract

Atomically precise thiolate-protected Cu nanoclusters (NCs) typically suffer from an intrinsic bias toward the two-electron formate pathway in CO₂ electroreduction, limiting access to more deeply reduced products. Breaking this selectivity within a structurally well-defined system remains a significant challenge due to the difficulty of precisely tuning the Cu valence states. Here, we address this limitation through atomic-level valence-state engineering by introducing [S@Cu₅₀S₁₂(S^tBu)₂₀(CF₃COO)₁₂] (S@Cu₅₀) NC, featuring a controlled Cu(I)/Cu(II) ratio within a conserved structural framework. Single-crystal analysis reveals a core–shell S@Cu₁₄S₁₂@Cu₃₆ architecture, while XPS confirms an increased Cu(II) population compared to the reference [Cu₅₀S₁₂(S^tBu)₂₀(CF₃COO)₁₂] (Cu₅₀) analogue. Despite similar overall catalytic activity, S@Cu₅₀ exhibits a striking shift in product selectivity during CO₂ electroreduction, suppressing formate formation (Faradaic efficiency of <11% vs 38% in Cu₅₀) and enabling CH₃OH production with a Faradaic efficiency of ∼19% at –1.0 V vs RHE─absent in the Cu₅₀ system. Density functional theory calculations attribute this mechanistic switching to valence-induced electronic modulation, which stabilizes CO-derived intermediates and promotes sequential hydrogenation toward CH₃OH, in contrast to HCOO stabilization in the reference NC. This work establishes that subtle modulation of the Cu(I)/Cu(II) balance can fundamentally redirect reaction pathways, providing a molecular-level strategy to overcome intrinsic selectivity limitations in Cu NC catalysis.