A fundamental understanding of interactions between catalysts and gas molecules is essential for the development of efficient heterogeneous catalysts. In this study, ambient pressure X-ray photoelectron spectroscopy (APXPS) and density functional theory (DFT) simulation were employed to investigate the activation of CO₂ on Cu surfaces, which acts as a key step in the catalytic reduction of CO₂. APXPS results show that CO₂ is adsorbed as CO₂^δ− on the Cu(111) surface under a pressure of 0.01 mbar at 300 K. Adsorbed CO₂^δ− gets partially transformed into carbonate with an increase of pressure to 1 mbar due to the disproportionation reaction between CO₂ molecules. Subsequent annealing of the Cu(111) surface in a CO₂ atmosphere leads to the dissociation of CO₂^δ− and carbonate, and a transformation to a chemisorbed oxygen covered surface occurred at 400 K and elevated temperatures. However, on the Cu(110) surface, the CO₂^δ− gradually dissociates to CO and chemisorbed oxygen in the presence of 1 mbar of CO₂ at room temperature. The self-deactivation of CO₂ adsorption due to the atomic oxygen generated by CO₂ dissociation is observed on both Cu(111) and Cu(110) surfaces. Moreover, these experimental results indicate that the Cu(110) surface is more active than the Cu(111) surface in breaking C–O bonds, which is consistent with the results of DFT simulations. Our findings indicate that the activation of CO₂ on Cu surfaces is strongly surface orientation- and pressure-dependent, which is an important step to clarify CO₂ activation mechanisms on Cu-based catalysts.

中文翻译：

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铜表面上CO ₂活化的表面取向和压力依赖性

对催化剂与气体分子之间相互作用的基本了解对于开发高效多相催化剂至关重要。在这项研究中，环境压力X射线光电子能谱法（APXPS）和密度泛函理论（DFT）模拟被雇用来调查CO的活化₂在Cu表面，其作为在催化还原CO的一个关键步骤₂。APXPS结果表明，CO ₂被吸附的CO ₂ ^δ- 0.01毫巴的在300K吸附CO的压力下在Cu（111）表面上的₂ ^δ-被部分地与增加的压力转化为碳酸盐至1mbar由于CO ₂之间的歧化反应分子。在CO在Cu（111）表面的后续退火₂气氛导致CO的解离₂ ^δ-和碳酸盐，和变换到化学吸附的氧气覆盖的表面发生在400度K和升高的温度。然而，在Cu（110）表面时，CO ₂ ^δ-逐渐离解成CO和在1毫巴的CO的化学吸附存在氧气₂在室温下。由于CO ₂产生的原子氧，CO ₂吸附的自失活在Cu（111）和Cu（110）表面均观察到解离。此外，这些实验结果表明，Cu（110）表面在打破C–O键方面比Cu（111）表面更具活性，这与DFT模拟的结果一致。我们的发现表明，Cu表面上的CO ₂活化与表面取向和压力密切相关，这是阐明Cu基催化剂上CO ₂活化机理的重要步骤。