文章基本信息

标题：Electron transfer between anatase TiO2 and an O2 molecule directly observed by atomic force microscopy
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作者：Martin Setvin ; Jan Hulva ; Gareth S. Parkinson 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：13
页码：E2556-E2562
DOI：10.1073/pnas.1618723114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Activation of molecular oxygen is a key step in converting fuels into energy, but there is precious little experimental insight into how the process proceeds at the atomic scale. Here, we show that a combined atomic force microscopy/scanning tunneling microscopy (AFM/STM) experiment can both distinguish neutral O₂ molecules in the triplet state from negatively charged (O₂)⁻ radicals and charge and discharge the molecules at will. By measuring the chemical forces above the different species adsorbed on an anatase TiO₂ surface, we show that the tip-generated (O₂)⁻ radicals are identical to those created when ( i ) an O₂ molecule accepts an electron from a near-surface dopant or ( ii ) when a photo-generated electron is transferred following irradiation of the anatase sample with UV light. Kelvin probe spectroscopy measurements indicate that electron transfer between the TiO₂ and the adsorbed molecules is governed by competition between electron affinity of the physisorbed (triplet) O₂ and band bending induced by the (O₂)⁻ radicals. Temperature–programmed desorption and X-ray photoelectron spectroscopy data provide information about thermal stability of the species, and confirm the chemical identification inferred from AFM/STM.
关键词：TiO₂ ; anatase ; AFM ; O₂ ; adsorption