Surface Science最新文献_第2页

Characterizing the surface compositions of supported bimetallic PtSn clusters: Effects of cluster-support interactions and surface adsorbates 表征支撑双金属铂锑团簇的表面成分：簇-支撑相互作用和表面吸附剂的影响

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-10-05 DOI: 10.1016/j.susc.2024.122623

PtSn bimetallic clusters on TiO₂(110) and highly oriented pyrolytic graphite (HOPG) surfaces have been characterized by scanning tunneling microscopy, low energy ion scattering (LEIS), X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD); density functional theory (DFT) calculations have also been performed to better understand adsorption of CO and D₂ on the PtSn surfaces. On TiO₂ at coverages of 2 ML of Pt and 2 ML of Sn, exclusively bimetallic clusters are formed for both orders of deposition because clusters of the first metal completely cover the surface such that all atoms of the second metal are incorporated into the existing clusters. In contrast, on HOPG, the high mobility and weak cluster-support interactions on HOPG result in much larger 2 ML monometallic clusters (∼30 Å high) that do not completely cover the surface, and deposition of the second metal produces larger clusters as well as smaller ones. Despite the difference in cluster morphologies for the different orders of deposition and supports, the LEIS experiments demonstrate that in all cases, the PtSn clusters are rich in Sn at the surface, as expected based on the lower surface free energy for Sn compared to Pt. Furthermore, the +0.2 eV shift in the Sn(3d_5/2) binding energy observed on all surfaces in the presence of Pt is consistent with PtSn alloy formation. Deposition of 2 ML of Sn on TiO₂ produces two-dimensional clusters with oxidation of Sn and reduction of titania at the cluster-support interface, but addition of Pt to the Sn clusters causes Sn to diffuse away from this interface, leaving Sn in the metallic state. TPD experiments on 2 ML Pt/TiO₂ with increasing coverages of Sn show that the number of adsorption sites for D₂ sharply decreases to nearly zero at 0.5 ML, while CO adsorption decreases to zero only at much higher Sn coverages of 2 ML. DFT studies for Sn modified Pt surfaces and bulk structures demonstrate that for CO adsorption at low Sn coverages (≤0.25 ML), the strong Pt-CO interactions induce diffusion of Pt to the cluster surface and the formation of a bulk Pt₃Sn alloy, whereas D₂ adsorption does not lead to interactions with the Pt surface that are strong enough to induce alloy formation. A single Sn adatom prevents D₂ adsorption on four neighboring Pt atoms via site-blocking and the donation of electron density to Pt.

通过扫描隧道显微镜、低能离子散射 (LEIS)、X 射线光电子能谱和温度编程解吸 (TPD) 对 TiO2(110) 和高取向热解石墨 (HOPG) 表面上的铂锰双金属团簇进行了表征；还进行了密度泛函理论 (DFT) 计算，以更好地了解 CO 和 D2 在铂锰表面的吸附情况。在铂的覆盖率为 2 ML 和锡的覆盖率为 2 ML 的 TiO2 上，两种沉积阶次都能形成完全的双金属簇，因为第一种金属的簇完全覆盖了表面，这样第二种金属的所有原子都融入了现有的簇中。与此相反，在 HOPG 上，由于 HOPG 的高迁移率和微弱的簇支撑相互作用，形成了大得多的 2 ML 单金属簇（高 30 Å），这些簇并没有完全覆盖表面，而第二种金属的沉积既会产生较大的簇，也会产生较小的簇。尽管不同沉积顺序和支持物的簇形态各异，但 LEIS 实验表明，在所有情况下，PtSn 簇表面都富含 Sn，这是基于 Sn 的表面自由能低于 Pt 所预期的。此外，在有 Pt 存在的情况下，所有表面上观察到的 Sn(3d5/2) 结合能都发生了 +0.2 eV 的移动，这与 PtSn 合金的形成是一致的。在二氧化钛上沉积 2 ML Sn 会产生二维簇，在簇-支撑界面上 Sn 被氧化，二氧化钛被还原，但在 Sn 簇中添加铂会导致 Sn 从该界面扩散开，使 Sn 处于金属态。在 Sn 覆盖率不断增加的 2 ML Pt/TiO2 上进行的 TPD 实验表明，D2 的吸附位点数量在 0.5 ML 时急剧下降至近乎为零，而 CO 的吸附只有在 Sn 覆盖率高达 2 ML 时才降至零。对 Sn 修饰的铂表面和块体结构进行的 DFT 研究表明，在低 Sn 覆盖率（≤0.25 ML）条件下吸附 CO 时，强烈的 Pt-CO 相互作用会诱导铂向簇表面扩散并形成块体 Pt3Sn 合金，而吸附 D2 不会导致与铂表面产生足以诱导合金形成的相互作用。单个锡原子通过位阻和向铂提供电子密度阻止了 D2 在四个相邻铂原子上的吸附。

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引用次数: 0

Alloying effects on the reactivity of Pd are ensemble dominated 合金对钯反应性的影响以集合效应为主

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-10-05 DOI: 10.1016/j.susc.2024.122620

In this paper the geometric (“ensemble”) and electronic (“ligand”) effects of alloying on surface reactivity and catalysis are considered. The effect of alloying on the behaviour of Pd, both in single crystal form, and as a nanoparticulate catalyst is discussed. The first case concerns Pd alloyed with Cu, and here the reactivity with formic acid and ethanol is modified by the presence of Cu. However, both Cu and Pd maintain their elemental integrity for the reactions, and it is shown that the main alloying effect is one of dilution of Pd atoms, rather than by global electronic factors such as d-band shifting and filling. Similarly, when Pd is alloyed with Au, then the adsorption characteristics (sticking probability and uptake) for CO, O₂, ethene and acetaldehyde are dominated by changes in the surface arrangement of the two atoms. Au mainly acts as an adsorption blocker, but to different degrees depending upon the nature of the adsorbing molecule and its demand for particular ensemble sizes. Finally, nanoparticulate Pd is considered, and the effect of alloying on high pressure methanol synthesis from CO₂ and H₂ is outlined. Pd on its own is not very selective, instead it mainly produces CO and methane. However, by supporting on oxides such as ZnO, Ga₂O₃ and In₂O₃ and by reducing in hydrogen, the Pd forms alloys, which then results in high selectivity to methanol. Again, this is ascribed to the dilution of the Pd ensembles at the surface, which are the cause of methane production.

本文探讨了合金化对表面反应性和催化作用的几何（"集合"）和电子（"配体"）效应。本文讨论了合金化对单晶钯和纳米颗粒催化剂行为的影响。第一种情况涉及与铜合金化的钯，铜的存在改变了钯与甲酸和乙醇的反应性。然而，铜和钯在反应中都保持了元素的完整性，这表明主要的合金效应是钯原子的稀释，而不是由 d 带移动和填充等全局电子因素造成的。同样，当 Pd 与 Au 合金时，CO、O2、乙烯和乙醛的吸附特性（粘附概率和吸附量）主要受两个原子表面排列变化的影响。金主要起吸附阻滞剂的作用，但程度不同，取决于吸附分子的性质及其对特定集合尺寸的需求。最后，我们考虑了纳米颗粒钯，并概述了合金化对二氧化碳和 H2 高压合成甲醇的影响。钯本身的选择性不强，相反，它主要产生 CO 和甲烷。然而，通过在 ZnO、Ga2O3 和 In2O3 等氧化物上进行支撑，以及在氢气中进行还原，钯会形成合金，从而对甲醇产生高选择性。这也是由于表面的钯集合体被稀释，从而产生了甲烷。

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引用次数: 0

Comparing phase sensitive detection and Fourier analysis of modulation excitation spectroscopy data exemplified by Ambient Pressure X-ray Photoelectron Spectroscopy 以常压 X 射线光电子能谱为例，比较相敏检测和调制激发光谱数据的傅里叶分析

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-10-01 DOI: 10.1016/j.susc.2024.122612

Dynamic processes in catalysis are gaining increased attention and could very well be one of the next frontiers in surface science. One way to study such processes is to induce chemical changes on the surface for example by periodically adjusting the (electro)chemical potential in situ and identify the resulting spectral changes. Often this is referred to as Modulation Excitation Spectroscopy (MES). Using Ambient Pressure Photoelectron Spectroscopy data, we here discuss and compare the analysis of MES data using both Phase Sensitive Detection (PSD) and Fourier analysis. We discuss that PSD determines the component magnitude at a user-defined phase value while Fourier analysis provides the maximum oscillation amplitude and respective phase value of oscillating spectral features. We discuss advantages and disadvantages of the different analysis schemes and explore how the full time-evolution can be obtained.

催化的动态过程越来越受到关注，很可能成为表面科学的下一个前沿领域。研究此类过程的一种方法是诱导表面发生化学变化，例如通过在原位定期调节（电）化学势，并识别由此产生的光谱变化。这通常被称为调制激发光谱（MES）。利用常压光电子能谱数据，我们在此讨论并比较使用相敏检测（PSD）和傅立叶分析对 MES 数据进行的分析。我们讨论了 PSD 可确定用户定义相位值的分量幅度，而傅里叶分析可提供振荡光谱特征的最大振荡幅度和各自的相位值。我们讨论了不同分析方案的优缺点，并探讨了如何获得完整的时间演变。

引用次数: 0

The surface chemistry of cuprous oxide 氧化亚铜的表面化学

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-10-01 DOI: 10.1016/j.susc.2024.122622

The chemical and electronic properties of copper combined with its large natural abundance lend this material to impact a wide range of technological applications, including heterogeneous catalysis. The reactivity of copper in its Cu¹⁺oxidation state makes this specific configuration relevant in various chemical reactions, but the facile redox properties of copper make the isolation of individual states for fundamental studies difficult. Here we review three Cu₂O model systems used to study the interaction of Cu¹⁺ with small molecules making use of surface science techniques: Cu₂O/Cu(111), thin polycrystalline Cu₂O films on Cu foil, and bulk Cu₂O crystals. Advantages and disadvantages of each system are discussed and exemplified through case studies of chemical adsorption and reactivity studies.

铜的化学和电子特性加上其巨大的天然丰度，使这种材料能够影响广泛的技术应用，包括异相催化。铜在 Cu1+ 氧化态时的反应活性使得这种特定构型与各种化学反应相关，但铜的易氧化还原特性使得分离单个态进行基础研究十分困难。在此，我们回顾了利用表面科学技术研究 Cu1+ 与小分子相互作用的三种 Cu2O 模型体系：Cu2O/Cu(111)、铜箔上的多晶 Cu2O 薄膜以及块状 Cu2O 晶体。通过对化学吸附和反应性研究的案例研究，讨论并举例说明了每种系统的优缺点。

引用次数: 0

CO oxidation on IrO2(110) surfaces IrO2（110）表面的 CO 氧化作用

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-29 DOI: 10.1016/j.susc.2024.122619

We investigated the oxidation of CO on stoichiometric and O-rich IrO₂(110) surfaces using temperature programmed reaction spectroscopy (TPRS), density functional theory (DFT) calculations and microkinetic simulations. Adsorbed CO on the s-IrO₂(110) surface generates CO and CO₂ peaks near 545 K during TPRS, and only about 38 % of the CO oxidized to CO₂ when the initial CO layer was saturated. Pre-adsorbed O-atoms, so-called on-top oxygen (O_t), promote the oxidation of CO adsorbed on IrO₂(110). On the O_t-covered surface, CO oxidation by O_t atoms produces a CO₂ TPRS peak at ∼370 K, and all of the initially adsorbed CO oxidizes to CO₂ when the initial O_t coverage is greater than the CO coverage. In agreement with the TPRS results, DFT calculations predict that the barrier is about 100 kJ/mol lower for CO oxidation by an O_t atom than a lattice O-atom of IrO₂(110). A microkinetic model, parameterized with energy barriers computed using DFT, accurately reproduces the CO and CO₂ TPRS traces only after CO binding energies are lowered to values determined using a hybrid exchange-correlation functional and the barrier for CO molecules to fill bridging O-vacancies is lowered. The simulations predict that O-vacancies play an important role in mediating the CO oxidation kinetics on s-IrO₂(110), and thereby demonstrate the importance of future spectroscopic studies aimed at characterizing the nature of the surface CO and O species involved in reaction. This study provides new insights for understanding CO oxidation on IrO₂(110), and provides evidence that several elementary steps can be involved in governing this chemistry.

我们利用温度编程反应光谱（TPRS）、密度泛函理论（DFT）计算和微动力学模拟研究了CO在化学计量和富含O的IrO2（110）表面上的氧化过程。在 TPRS 过程中，s-IrO2(110) 表面吸附的 CO 在 545 K 附近产生 CO 和 CO2 峰，当初始 CO 层饱和时，只有约 38% 的 CO 氧化成 CO2。预先吸附的 O 原子，即所谓的顶部氧（Ot），促进了吸附在 IrO2（110）上的 CO 的氧化。在Ot覆盖的表面上，Ot原子对CO的氧化作用会在∼370 K时产生一个CO2 TPRS峰，当初始Ot覆盖率大于CO覆盖率时，所有初始吸附的CO都会氧化成CO2。与 TPRS 结果一致，DFT 计算预测，Ot 原子氧化 CO 的势垒比 IrO2(110) 晶格 O 原子氧化 CO 的势垒低约 100 kJ/mol。只有在一氧化碳结合能降低到使用混合交换相关函数确定的值以及一氧化碳分子填充桥接 O-空位的障碍降低之后，使用 DFT 计算的能垒参数化的微动力学模型才能准确地再现一氧化碳和二氧化碳的 TPRS 轨迹。模拟预测 O-空位在介导 s-IrO2(110)上的 CO 氧化动力学中发挥了重要作用，从而证明了未来旨在确定参与反应的表面 CO 和 O 物种性质的光谱研究的重要性。这项研究为理解二氧化钛（IrO2）(110) 上的一氧化碳氧化作用提供了新的视角，并提供了证据，证明这一化学反应可能涉及几个基本步骤。

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引用次数: 0

Stability and dissolution of single-crystalline iron oxide thin films in electrochemical environments 单晶氧化铁薄膜在电化学环境中的稳定性和溶解性

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-29 DOI: 10.1016/j.susc.2024.122621

The stability of single-crystalline monolayer FeO(111) and 10 nm thin Fe₃O₄(111) films on Pt(111) upon exposure to environments of increasing chemical complexity has been studied with X-ray photoelectron spectroscopy, temperature-programmed desorption, in-situ scanning tunneling microscopy, and cyclic voltammetry. The well-defined oxide films, which were prepared under ultrahigh-vacuum conditions, were exposed to aqueous solutions of different pH and electrochemical cycling in pure and catechol-containing electrolyte. The films are stable in neutral (pH 7) and alkaline (pH 13) solutions both at open circuit conditions and during electrochemical cycling within the limits of hydrogen and oxygen evolution potentials. Also in strongly acidic (pH 1) perchlorate solution the films remain intact under open circuit conditions, but they quickly dissolve on application of electrochemical potential. Especially for the ultrathin FeO(111) films, catechol enhances the dissolution at neutral pH during electrochemical cycling. A comparison of Pt(111), FeO(111) and Fe₃O₄(111) substrates in the electrochemical catechol oxidation reaction reveals enhanced and sustained activity of FeO in alkaline environment, while strong deactivation occurs on Pt(111) and Fe₃O₄(111). This is explained by the weaker interaction between catechol and FeO(111) compared to the other substrates, which hampers the formation of a barrier layer on the electrode surface.

通过 X 射线光电子能谱、温度编程解吸、原位扫描隧道显微镜和循环伏安法，研究了铂(111)上单晶单层 FeO(111) 和 10 nm 薄 Fe3O4(111) 膜在化学复杂性不断增加的环境中的稳定性。在超高真空条件下制备的定义明确的氧化物薄膜暴露于不同 pH 值的水溶液中，并在纯电解液和含邻苯二酚的电解液中进行电化学循环。在中性（pH 值为 7）和碱性（pH 值为 13）溶液中，薄膜在开路条件下和电化学循环过程中在氢和氧进化电位范围内都很稳定。此外，在强酸性（pH 值为 1）高氯酸盐溶液中，薄膜在开路条件下保持完好，但在施加电化学势时会迅速溶解。特别是对于超薄的 FeO(111) 薄膜，在电化学循环过程中，邻苯二酚会增强薄膜在中性 pH 值下的溶解。通过比较 Pt(111)、FeO(111)和 Fe3O4(111)基底在电化学儿茶酚氧化反应中的作用，发现 FeO 在碱性环境中的活性增强且持续，而 Pt(111) 和 Fe3O4(111) 则出现强烈的失活现象。这是因为与其他基底相比，邻苯二酚与 FeO(111) 之间的相互作用较弱，阻碍了电极表面阻挡层的形成。

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引用次数: 0

Hydroxylation of an ultrathin Co3O4(111) film on Ir(100) studied by in situ ambient pressure XPS and DFT 通过原位常压 XPS 和 DFT 研究 Ir(100) 上超薄 Co3O4(111) 薄膜的羟基化过程

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-26 DOI: 10.1016/j.susc.2024.122618

In the present work, we have studied the interaction of water with spinel cobalt oxide (Co₃O₄), an effect which has been considered a major cause of its catalytic deactivation. Employing a Co₃O₄(111) model thin film grown on Ir(100) in (ultra)high vacuum, and ambient pressure X-ray photoelectron spectroscopy (APXPS), hydroxylation in 0.5 mbar H₂O vapor at room temperature was monitored in real time. The surface hydroxyl (OH) coverage was determined via two different models based (i) on the termination of a pristine and OH-covered Co₃O₄(111) surface as derived from density functional theory (DFT) calculations, and (ii) on a homogeneous cobalt oxyhydroxide (CoO(OH)) overlayer. Langmuir pseudo-second-order kinetics were applied to characterize the OH evolution with time, suggesting two regimes of chemisorption at the mosaic-like Co₃O₄(111) film: (i) plateaus, which were quickly saturated by OH, followed by (ii) slow hydroxylation in the “cracks” of the thin film. H₂O dissociation and OH formation, blocking exposed Co²⁺ ions and additionally consuming surface lattice oxygen, respectively, may thus account for catalyst deactivation by H₂O traces in reactive feeds.

在本研究中，我们研究了水与尖晶石氧化钴（Co3O4）的相互作用，这种作用一直被认为是导致其催化失活的主要原因。利用在（超）高真空条件下在 Ir（100）上生长的 Co3O4（111）模型薄膜和环境压力 X 射线光电子能谱（APXPS），对室温下 0.5 毫巴 H2O 蒸汽中的羟基化进行了实时监测。通过两种不同的模型确定了表面羟基（OH）的覆盖率，这两种模型分别基于（i）密度泛函理论（DFT）计算得出的原始表面和羟基覆盖的 Co3O4（111）表面的终止，以及（ii）均匀的氧氢氧化钴（CoO（OH））覆盖层。兰缪尔假秒阶动力学用于描述 OH 随时间的演化过程，表明在镶嵌状 Co3O4(111) 薄膜上存在两种化学吸附状态：(i) 高原，OH 迅速饱和；(ii) 薄膜 "裂缝 "中的缓慢羟基化。因此，H2O 解离和 OH 形成分别阻挡了暴露在外的 Co2+ 离子，并额外消耗了表面晶格氧，这可能是反应性进料中 H2O 痕迹导致催化剂失活的原因。

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引用次数: 0

Interfacial effect investigation of lithium perchlorate-interacted oxygen-containing carbon paper 高氯酸锂与含氧碳纸的界面效应研究

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-21 DOI: 10.1016/j.susc.2024.122615

The lithium perchlorate-interacted oxygen-containing carbon paper (LiClO4-OCP) is designed to act as electroactive supercapacitor electrode substrates for the energy storage application. The OCP is fabricated through hydrothermal activation treatment of carbon paper in H₂O₂ reaction medium. The OCP is composed of graphite pitches with ultra-thin graphene structure of top layer, showing the improved graphitization degree. The LiClO4-OCP with the polarized electrostatic force-induced interfacial adsorption reveals much more intensive interaction than LiClO4-CP with van der Waals force-induced interfacial adsorption, contributing to promoting interfacial charge transfer of LiClO4-OCP. LiClO4-OCP reveals more effective interface charge transfer and more feasible electrolyte diffusion than LiClO4-CP, contributing to higher electrochemical double-layer capacitance. LiClO4-OCP with oxygen-containing groups conducts reversible redox process to supply additional Faradaic capacitance. Mean response current is increased from 0.10 ∼ 1.34 mA cm^-2 for LiClO4-CP to 0.19 ∼ 2.31 mA cm^-2 for LiClO4-OCP at scan rates of 5∼100 mV s^-1, indicating the improved electrochemical activity of LiClO4-OCP. The cyclic voltammetry-based capacitance increases from 19.91 ∼ 13.01 mF cm^-2 mF g-1 for LiClO4-CP to 37.76 ∼ 23.06 mF cm^-2 for LiClO4-OCP. The galvanostatic charge/discharge-based capacitance decreases from 13.84 ∼ 3.97 mF cm^-2 for LiClO4-CP to 29.71 ∼ 12.92 mF cm^-2 for LiClO4-OCP. Density-functional theory-based simulation calculation proves LiClO4-OCP with such a short molecular distance is allowed to occur strong electrostatic interaction which is caused by the perchlorate ion-induced polarization of oxygen-containing groups. The LiClO4-OCP has lower interfacial energy, lower band gap and higher density of states at Fermi energy level than LiClO4-CP, indicating the improved interfacial interaction and electrical conductivity of LiClO4-OCP. The experimental measurement and theoretical calculation achieve the consistent results of higher electrochemical activity of LiClO4-OCP electrode substrate to present its superior capacitance performance.

与高氯酸锂相互作用的含氧碳纸（LiClO4-OCP）被设计为具有电活性的超级电容器电极基板，用于储能应用。OCP 是通过在 H2O2 反应介质中对碳纸进行水热活化处理制成的。OCP 由石墨间距组成，表层为超薄石墨烯结构，石墨化程度更高。极化静电力诱导界面吸附的 LiClO4-OCP 比范德华力诱导界面吸附的 LiClO4-CP 显示出更强烈的相互作用，有助于促进 LiClO4-OCP 的界面电荷转移。与 LiClO4-CP 相比，LiClO4-OCP 显示出更有效的界面电荷转移和更可行的电解质扩散，因而具有更高的电化学双层电容。含有含氧基团的 LiClO4-OCP 可进行可逆的氧化还原过程，从而提供额外的法拉第电容。在扫描速率为 5∼100 mV s-1 时，平均响应电流从 LiClO4-CP 的 0.10 ∼ 1.34 mA cm-2 增加到 LiClO4-OCP 的 0.19 ∼ 2.31 mA cm-2，表明 LiClO4-OCP 的电化学活性有所提高。基于循环伏安法的电容从 LiClO4-CP 的 19.91 ∼ 13.01 mF cm-2 mF g-1 增加到 LiClO4-OCP 的 37.76 ∼ 23.06 mF cm-2。电静态充放电电容从 LiClO4-CP 的 13.84 ∼ 3.97 mF cm-2 下降到 LiClO4-OCP 的 29.71 ∼ 12.92 mF cm-2。基于密度泛函理论的模拟计算证明，分子距离如此之短的 LiClO4-OCP 可以发生强烈的静电作用，这种作用是由高氯酸根离子引起的含氧基团极化造成的。与 LiClO4-CP 相比，LiClO4-OCP 具有更低的界面能、更低的带隙和更高的费米能级态密度，这表明 LiClO4-OCP 的界面相互作用和导电性能得到了改善。实验测量和理论计算的结果一致，LiClO4-OCP 电极衬底具有更高的电化学活性，从而显示出其优越的电容性能。

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引用次数: 0

The evolution of model Rh/Fe3O4(001) catalysts in hydrogen environments 模型 Rh/Fe3O4(001) 催化剂在氢环境中的演变

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-20 DOI: 10.1016/j.susc.2024.122617

Single metal atoms dispersed on oxides are a new emerging class of catalysts owing to their unique electronic and chemical properties. In this study, we have prepared a series of model single-atom catalysts possessing well-characterized Rh sites that include Rh adatoms (Rh_ad), mixed surface layers with octahedrally-coordinated Rh (Rh_oct), as well as metallic Rh clusters and nanoparticles (Rh_met) on Fe₃O₄(001). Using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we investigated the activity of such model systems towards H₂ and their stability in reducing environments. Our results show that the atomically dispersed Rh_ad and Rh_oct species do not activate H_2, which would result in the formation of surface hydroxyls on Fe₃O₄(001). In contrast, the presence of Rh_met in H₂ results in the formation of hydroxyls and subsequent etching of the Fe₃O₄(001) at higher temperatures (≥ 500 K) due to water formation via the Mars−van Krevelen mechanism. Additionally, such surface etching leads to the release of the Rh_oct from the surface lattice and their sintering to Rh_met. To bridge the material gap between the surface science models and high surface area catalysts, we perform parallel studies on powder Rh/Fe₃O₄ catalysts. The XPS characterization shows remarkable similarities between these systems. Further, our surface science studies provide an atomistic picture of the behavior of high surface area catalysts in the H₂ atmosphere.

分散在氧化物上的单金属原子因其独特的电子和化学特性而成为一类新兴催化剂。在本研究中，我们在 Fe3O4(001) 上制备了一系列具有特征良好的 Rh 位点的模型单原子催化剂，这些位点包括 Rh adatoms (Rhad)、八面体配位的 Rh 混合表层 (Rhoct)，以及金属 Rh 簇和纳米颗粒 (Rhmet)。我们利用 X 射线光电子能谱 (XPS) 和扫描隧道显微镜 (STM) 研究了这些模型系统对 H2 的活性及其在还原环境中的稳定性。结果表明，原子分散的 Rhad 和 Rhoct 物种不会激活 H2，从而导致在 Fe3O4(001) 上形成表面羟基。相反，Rhmet 在 H2 中的存在会导致羟基的形成，随后在较高温度下（≥ 500 K），由于通过 Mars-van Krevelen 机制形成的水，Fe3O4(001)会被蚀刻。此外，这种表面蚀刻会导致 Rhoct 从表面晶格中释放出来，并烧结成 Rhmet。为了缩小表面科学模型与高比表面积催化剂之间的材料差距，我们对 Rh/Fe3O4 粉末催化剂进行了平行研究。XPS 表征显示了这些体系之间的显著相似性。此外，我们的表面科学研究还提供了高比表面积催化剂在 H2 大气中行为的原子图景。

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引用次数: 0

Evolution of the surface morphology of GaSb epitaxial layers deposited by molecular beam epitaxy (MBE) on GaAs (100) substrates 通过分子束外延 (MBE) 沉积在砷化镓（100）衬底上的 GaSb 外延层的表面形貌演变

IF 2.1 4区化学 Q3 CHEMISTRY, PHYSICAL

Surface Science

Pub Date : 2024-09-19 DOI: 10.1016/j.susc.2024.122607

This study presents a demonstration of the surface morphology behavior of gallium antimonide (GaSb) layers deposited on gallium arsenide (GaAs) (100) substrates using three different methods: metamorphic, interfacial misfit (IMF) matrix, and a method based on a Polish patent application number P.443805. The first two methods are commonly used, while the third differs in the sequence of successive steps and the presence of Be doping at the initial growth stage. By comparing GaSb layers made by these methods for the same growth parameters, the most favorable procedure for forming a GaSb buffer layer is selected. Using GaAs substrates with a GaSb buffer layer is a cheaper alternative to using GaSb substrates in infrared detector structures based on II-type superlattices T2SL, such as InAs/GaSb. The quality of the GaSb buffer layer determines the quality of the subsequent layers that form the entire T2SL and affects factors such as dark current in terms of application.

本研究展示了使用三种不同方法在砷化镓（GaAs）（100）基底上沉积锑化镓（GaSb）层的表面形态行为：变质法、界面错位（IMF）基质法和基于波兰专利申请号 P.443805 的方法。前两种方法是常用的，而第三种方法的不同之处在于连续步骤的顺序以及在初始生长阶段掺入 Be 的情况。通过比较在相同生长参数下用这些方法制造的镓硒化物层，可以选择最有利于形成镓硒化物缓冲层的程序。在基于 II 型超晶格 T2SL（如 InAs/GaSb）的红外探测器结构中，使用带有 GaSb 缓冲层的 GaAs 衬底比使用 GaSb 衬底更便宜。GaSb 缓冲层的质量决定了构成整个 T2SL 的后续层的质量，并影响暗电流等应用因素。

引用次数: 0