Chang Chia-Jui, Hung Sung-Fu, Hsu Chia-Shuo, Chen Hsiao-Chien, Lin Sheng-Chih, Liao Yen-Fa, Chen Hao Ming
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
ACS Cent Sci. 2019 Dec 26;5(12):1998-2009. doi: 10.1021/acscentsci.9b01142. Epub 2019 Dec 11.
Oxide-derived copper catalysts have been shown to enhance CO reduction reaction (CORR) activity with high selectivity toward hydrocarbon products. However, the chemical state of oxide-derived copper during the CORR has remained elusive and is lacking in situ observations. Herein, a two-step process was developed to synthesize Ag nanowires coated with various thicknesses of a CuO layer for the CORR. By employing in situ X-ray absorption spectroscopy, a strong correlation between the chemical state under reaction conditions and the CORR product profile can be revealed to validate another competing reaction (i.e., the spontaneous oxidation of Cu(0) in aqueous electrolyte) that significantly governs the chemical state of active centers of Cu. In situ Raman spectroscopy reveals the existence of reoxidation behavior under cathodic potential, and the quantification analysis of reoxidized behavior is revealed to indicate that the reoxidation rate is independent of surface morphology and strongly proportional to the electrochemically surface area. The steady oxidation state of Cu in an in situ condition is the paramount key and dominates the products' profile of the CORR rather than other factors (e.g., crystal facets, atomic arrangements, morphology, elements) that have been investigated in numerous reports.
氧化物衍生的铜催化剂已被证明可提高一氧化碳还原反应（CORR）的活性，并对烃类产物具有高选择性。然而，CORR过程中氧化物衍生铜的化学状态仍不明确，且缺乏原位观察。在此，开发了一种两步法来合成涂覆有不同厚度CuO层的Ag纳米线用于CORR。通过使用原位X射线吸收光谱，可以揭示反应条件下的化学状态与CORR产物分布之间的强相关性，以验证另一种显著影响Cu活性中心化学状态的竞争反应（即Cu(0)在水性电解质中的自发氧化）。原位拉曼光谱揭示了阴极电位下再氧化行为的存在，并且对再氧化行为的定量分析表明，再氧化速率与表面形态无关，且与电化学表面积强烈成正比。原位条件下Cu的稳定氧化态是至关重要的关键因素，它主导着CORR的产物分布，而不是众多报告中所研究的其他因素（例如晶面、原子排列、形态、元素）。
