Ethylene epoxidation is one of the fundamental industrial reactions, garnering extensive theoretical and experimental studies. While silver has traditionally been the catalyst of choice for this reaction, copper has received comparatively little attention. In this study, we apply a coverage-dependent microkinetic modeling to quantitatively investigate ethylene epoxidation on Cu(111), serving as a model system to study the intrinsic activity and selectivity of Cu catalysts. The coverage-dependent simulation takes into account both self and cross-interactions of adsorbates, as well as the coverage effects on the transition states of each elementary step. In contrast, the coverage-independent modeling is conducted without considering coverage effects. We observe that the coverage-dependent modelling reveals the Cu(111) surface with coverage exceeding 30% oxygen atoms with a high turnover frequency (log(TOF) = 2.65) at 500 K. In contrast, the coverage-independent results indicate the Cu(111) surface being completely covered by oxygen atoms, leading to detrimental poisoning effects (log(TOF) = −2.47). We show that the EO selectivity on Cu(111) can be at a high level of 80% under all studied conditions in contrast to only ∼40% EO selectivity on Ag(111). Detailed structural analyses unveil the fundamental reasons why Cu catalysts are more selective for ethylene epoxidation. Furthermore, we suggest that reducing temperature and increasing oxygen pressure can effectively improve EO selectivity for industrial ethylene epoxidation.

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全面了解铜催化剂上的乙烯环氧化反应：具有覆盖效应的微动力学研究


乙烯环氧化是基本的工业反应之一，得到了广泛的理论和实验研究。虽然银传统上一直是该反应的首选催化剂，但铜受到的关注相对较少。在本研究中，我们应用覆盖率依赖的微动力学模型来定量研究Cu(111)上的乙烯环氧化反应，作为研究Cu催化剂的本征活性和选择性的模型系统。依赖于覆盖率的模拟考虑了吸附物的自身相互作用和交叉相互作用，以及覆盖率对每个基本步骤的过渡态的影响。相反，与覆盖无关的建模是在不考虑覆盖效应的情况下进行的。我们观察到，覆盖率相关的模型揭示了 Cu(111) 表面的覆盖率超过 30% 的氧原子，并且在 500 K 时具有高周转频率 (log(TOF) = 2.65)。相反，覆盖率无关的结果表明 Cu （111）表面完全被氧原子覆盖，导致有害的中毒效应（log（TOF）= -2.47）。我们表明，在所有研究条件下，Cu(111) 上的 EO 选择性可以达到 80% 的高水平，而 Ag(111) 上的 EO 选择性仅为 ∼40%。详细的结构分析揭示了铜催化剂对乙烯环氧化更具选择性的根本原因。此外，我们认为降低温度和增加氧气压力可以有效提高工业乙烯环氧化的EO选择性。