Oxidation State and Surface Reconstruction of Cu under CO2 Reduction Conditions from In Situ X-ray Characterization,Journal of the American Chemical Society

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Oxidation State and Surface Reconstruction of Cu under CO2 Reduction Conditions from In Situ X-ray Characterization
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-12-31 , DOI: 10.1021/jacs.0c10017
Soo Hong Lee , John C. Lin _{1,

2} , Maryam Farmand , Alan T. Landers _{2,

3} , Jeremy T. Feaster _{1,

2} , Jaime E. Avilés Acosta _{2,

4} , Jeffrey W. Beeman , Yifan Ye ₅ , Junko Yano ₆ , Apurva Mehta ₇ , Ryan C. Davis ₇ , Thomas F. Jaramillo _{1,

2} , Christopher Hahn ₂ , Walter S. Drisdell

Affiliation

The electrochemical CO2 reduction reaction (CO2RR) using Cu-based catalysts holds great potential for producing valuable multi-carbon products from renewable energy. However, the chemical and structural state of Cu catalyst surfaces during the CO2RR remains a matter of debate. Here, we show the structural evolution of the near-surface region of polycrystalline Cu electrodes under in situ conditions through a combination of grazing incidence X-ray absorption spectroscopy (GIXAS) and X-ray diffraction (GIXRD). The in situ GIXAS reveals that the surface oxide layer is fully reduced to metallic Cu before the onset potential for CO2RR, and the catalyst maintains the metallic state across the potentials relevant to the CO2RR. We also find a preferential surface reconstruction of the polycrystalline Cu surface toward (100) facets in the presence of CO2. Quantitative analysis of the reconstruction profiles reveals that the degree of reconstruction increases with increasingly negative applied potentials, and it persists when the applied potential returns to more positive values. These findings show that the surface of Cu electrocatalysts is dynamic during the CO2RR, and emphasize the importance of in situ characterization to understand the surface structure and its role in electrocatalysis.

中文翻译：

原位 X 射线表征在 CO2 还原条件下铜的氧化状态和表面重建

使用铜基催化剂的电化学 CO2 还原反应 (CO2RR) 具有从可再生能源生产有价值的多碳产品的巨大潜力。然而，在 CO2RR 过程中 Cu 催化剂表面的化学和结构状态仍然是一个有争议的问题。在这里，我们通过掠入射 X 射线吸收光谱 (GIXAS) 和 X 射线衍射 (GIXRD) 的组合，展示了原位条件下多晶铜电极近表面区域的结构演变。原位 GIXAS 表明，在 CO2RR 的起始电位之前，表面氧化物层完全还原为金属 Cu，并且催化剂在与 CO2RR 相关的电位上保持金属状态。我们还发现在 CO2 存在下，多晶 Cu 表面朝向（100）面的优先表面重建。重建剖面的定量分析表明，重建程度随着施加的负电位的增加而增加，并且当施加的电位恢复到更正的值时它会持续存在。这些发现表明，在 CO2RR 过程中，Cu 电催化剂的表面是动态的，并强调了原位表征对了解表面结构及其在电催化中的作用的重要性。

更新日期：2020-12-31

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