In the electrochemical CO₂ reduction reaction (CO₂RR), Cu has been spotlighted as the only electro-catalyst that can produce multi-carbon molecules, but the mechanism of the selective C₂₊ production reaction remains elusive. Here, we directly monitored CO₂RR intermediates by employing time-resolved attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS), with particular attention to the C₁ and C₂₊ pathways beyond the formation of *CO. Electrodeposited Cu and Cu(OH)₂-derived Cu were synthesized, and subsequently employed as a C₁ and C₂₊ activating catalyst and C₂₊ activating catalyst, respectively. For the first time, a kinetically linked dimer intermediate (*OCCO) was observed and identified as the C₂₊ path triggering intermediate. The ATR-SEIRAS results suggest that C–C coupling occurs exclusively by CO dimerization toward *OCCO, without the participation of *CHO, which is an intermediate for CH₄ production. In the real-time measurements, CO dimerization occurred concurrently with CO adsorption (∼5 s), while proton-coupled reduction toward *CHO has slower kinetics (∼30 s). We demonstrated that the sites showing a high vibrational frequency of *CO on the fragmented Cu surface are the potential active sites for the fast dimerization of CO. This work provides mechanistic insights into the CO₂RR pathways and enables the design of efficient C₂₊-producing catalysts.

中文翻译：

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时间分辨观察铜电极上CC偶联中间物的选择性电化学还原CO2的时间

在电化学的CO ₂还原反应（CO ₂ RR）中，Cu被认为是唯一可以产生多碳分子的电催化剂，但是选择性C ₂₊产生反应的机理仍然难以捉摸。在这里，我们通过采用时间分辨的衰减全反射面增强红外吸收光谱（ATR-SEIRAS）直接监视CO ₂ RR中间体，尤其要注意* CO形成后的C ₁和C ₂₊途径。合成了电沉积的Cu和衍生自Cu（OH）_2的Cu，然后将其用作C ₁和C ₂₊活化催化剂和C分别为₂₊活化催化剂。首次观察到动力学连接的二聚体中间体（* OCCO），并将其鉴定为触发C ₂₊路径的中间体。ATR-SEIRAS结果表明，CC耦合仅通过向* OCCO的CO二聚而发生，而没有* CHO参与，后者是CH ₄生产的中间体。在实时测量中，CO二聚化与CO吸附同时发生（约5 s），而质子耦合向* CHO的还原反应动力学较慢（约30 s）。我们证明了在破碎的Cu表面上* CO振动频率高的位点是CO快速二聚化的潜在活性位点。这项工作提供了对CO _2的机械洞察力。RR途径使高效C _2+生成催化剂的设计成为可能。