Mu Shijia, Lu Honglei, Wu Qianbao, Li Lei, Zhao Ruijuan, Long Chang, Cui Chunhua
Molecular Electrochemistry Laboratory, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054, China.
Nat Commun. 2022 Jun 27;13(1):3694. doi: 10.1038/s41467-022-31498-8.
Cu sites on the surface of oxide-derived copper (OD-Cu) are of vital importance in electrochemical CO reduction reaction (CORR). However, the underlying reason for the dynamically existing Cu species, although thermodynamically unstable under reductive CORR conditions, remains uncovered. Here, by using electron paramagnetic resonance, we identify the highly oxidative hydroxyl radicals (OH) formed at room temperature in HCO solutions. In combination with in situ Raman spectroscopy, secondary ion mass spectrometry, and isotope-labelling, we demonstrate a dynamic reduction/reoxidation behavior at the surface of OD-Cu and reveal that the fast oxygen exchange between HCO and HO provides oxygen sources for the formation of OH radicals. In addition, their continuous generations can cause spontaneous oxidation of Cu electrodes and produce surface CuO species. Significantly, this work suggests that there is a "seesaw-effect" between the cathodic reduction and the OH-induced reoxidation, determining the chemical state and content of Cu species in CORR. This insight is supposed to thrust an understanding of the crucial role of electrolytes in CORR.
氧化物衍生铜（OD-Cu）表面的铜位点在电化学CO还原反应（CORR）中至关重要。然而，尽管在还原性CORR条件下热力学不稳定，但动态存在的铜物种的潜在原因仍未被揭示。在这里，通过电子顺磁共振，我们识别出在HCO溶液中室温下形成的高氧化性羟基自由基（OH）。结合原位拉曼光谱、二次离子质谱和同位素标记，我们证明了OD-Cu表面的动态还原/再氧化行为，并揭示了HCO和HO之间快速的氧交换为OH自由基的形成提供了氧源。此外，它们的持续产生会导致铜电极的自发氧化并产生表面CuO物种。值得注意的是，这项工作表明在阴极还原和OH诱导的再氧化之间存在“跷跷板效应”，这决定了CORR中铜物种的化学状态和含量。这一见解有望推动对电解质在CORR中关键作用的理解。
