Charge transfer at interfaces of copper clusters on TiO2(110) and SiOx

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
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Abstract

Metal nanoparticles supported on different oxidic supports are the most common materials in heterogeneous (photo-)catalysis. This work presents a systematic investigation of copper clusters deposited onto slightly and highly reduced rutile TiO2(110) single crystals and silicon wafers with native oxide films. The focus is on the electronic properties of the copper clusters and possible metal-support interactions as these can change the catalytic behavior of the catalyst. Specifically, we examine coverage-dependent core-level binding energy shifts and kinetic energy Auger signal shifts of the Cu2p3/2 and CuLMM signals in X-ray photoelectron spectroscopy as well as a Wagner plot analysis, Auger parameter analysis, and analyze the main support signals. The final-state-induced binding energy shifts dominant at lower coverages are related to the imperfect core-hole shielding of the positive charge remaining after photoemission. At higher copper coverages the more metallic character of the clusters, apparent from dominating initial-state effects, is more prominent. The shift in binding energy, kinetic energy, and Auger parameter are larger for copper on silica than for copper on reduced titania. The formation of Ti3+ or Si3+ indicates a charge transfer from the metal clusters to the support. For the first nominal monolayer of copper on titania a constant number of Ti3+ interstitials of 6% to 8% were observed regardless of the initial reduction degree of the titania. At the highest copper coverage, the local Ti3+ density at the (sub)surface increases to 11.0% and 11.7%. For the SiOx surface the same could be observed as the Si3+/Si4+ ratio increased from 4% at the lowest copper coverage to 73% at the highest. For the inert SiOx surface, we suggest an interaction of the copper with defects in the amorphous thin film.

Abstract Image

TiO2(110) 和 SiOx 上铜簇界面的电荷转移
支撑在不同氧化支撑物上的金属纳米颗粒是异相(光)催化中最常见的材料。本研究对沉积在轻度和高度还原的金红石型 TiO2(110)单晶和带有原生氧化膜的硅晶片上的铜簇进行了系统研究。研究的重点是铜簇的电子特性和可能的金属-支撑相互作用,因为这些会改变催化剂的催化行为。具体来说,我们研究了 X 射线光电子能谱中与覆盖有关的核心级结合能移动和动能奥杰信号移动,以及瓦格纳图分析和奥杰参数分析,并分析了主要支撑信号。在较低的铜覆盖率下,最终状态引起的结合能偏移占主导地位,这与光辐射后剩余正电荷的不完全芯孔屏蔽有关。在较高的铜覆盖率下,从占主导地位的初始状态效应中可以明显看出,团簇的金属特性更为突出。与还原钛上的铜相比,二氧化硅上的铜在结合能、动能和奥杰参数上的变化更大。Ti3+ 或 Si3+ 的形成表明电荷从金属簇转移到了支持物上。对于二氧化钛上的第一个单层铜,无论二氧化钛的初始还原度如何,都能观察到 6% 至 8% 的恒定数量的 Ti3+ 间隙。铜覆盖率最高时,(亚)表面的局部 Ti3+ 密度增至 11.0% 和 11.7%。对于氧化硅表面,同样可以观察到 Si3+/Si4+ 比率从最低铜覆盖率时的 4% 增加到最高覆盖率时的 73%。对于惰性氧化硅表面,我们认为铜与无定形薄膜中的缺陷相互作用。
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来源期刊
Surface Science
Surface Science 化学-物理:凝聚态物理
CiteScore
3.30
自引率
5.30%
发文量
137
审稿时长
25 days
期刊介绍: Surface Science is devoted to elucidating the fundamental aspects of chemistry and physics occurring at a wide range of surfaces and interfaces and to disseminating this knowledge fast. The journal welcomes a broad spectrum of topics, including but not limited to: • model systems (e.g. in Ultra High Vacuum) under well-controlled reactive conditions • nanoscale science and engineering, including manipulation of matter at the atomic/molecular scale and assembly phenomena • reactivity of surfaces as related to various applied areas including heterogeneous catalysis, chemistry at electrified interfaces, and semiconductors functionalization • phenomena at interfaces relevant to energy storage and conversion, and fuels production and utilization • surface reactivity for environmental protection and pollution remediation • interactions at surfaces of soft matter, including polymers and biomaterials. Both experimental and theoretical work, including modeling, is within the scope of the journal. Work published in Surface Science reaches a wide readership, from chemistry and physics to biology and materials science and engineering, providing an excellent forum for cross-fertilization of ideas and broad dissemination of scientific discoveries.
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