Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology and environmental studies, as it is closely linked to both catalytic activity and material degradation. The atomic-scale details are mostly unknown, however, and are often ascribed to poorly defined defects in the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, we show that all the 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline r-cut (1-102) surface of hematite (α-Fe2O3) are exchanged with oxygen from surrounding water vapor within minutes at temperatures below 70 °C, while the atomic-scale surface structure is unperturbed by the process. A similar behavior is observed after liquid water exposure, but the experimental data clearly show most of the exchange happens during desorption of the final monolayer, not during immersion. Density functional theory computations show that the exchange can happen during on-surface diffusion, where the cost of the lattice oxygen extraction is compensated by the stability of an HO-HOH-OH complex. Such insights into lattice oxygen stability are highly relevant for many research fields ranging from catalysis and hydrogen production to geochemistry and paleoclimatology.
Oxygen-Pressure-Limited Recovery of the Hematite α-Fe$_2$O$_3$(0001) Surface from a Reduced Fe$_3$O$_4$(111)-Like Layer
CEITEC - Central European Institute of Technology, Brno University of Technology（中欧技术研究所，布尔诺理工大学）；Institute of Physical Engineering, Brno University of Technology（物理工程系，布尔诺理工大学）
Effect of Defects on the Small Polaron Formation and Transport Properties of Hematite from First-Principles Calculations
赤铁矿（$α$ $_2$ O $_3$）由于其对可见光吸收有利的带隙、其在水性环境中的稳定性以及与其他有前景的材料相比其相对低的成本而成为用于太阳能到燃料转换的光阳极材料的有希望的候选者。然而，$α$ $_2$ O $_3$中的小极化子输运性质导致低载流子迁移率和电导率，显著降低了其理论极限的效率.在实验上，已经发现，将氧空位和其他掺杂剂（例如Sn）并入材料中明显地提高了其光电流效率。然而，没有定量的解释已经提供了理解的作用，氧空位或锡掺杂的赤铁矿。采用密度泛函理论研究了贫氧、掺氮和掺锡的赤铁矿中小极化子的形成。我们计算了带电缺陷形成能、小极化子形成能和跳跃激活能，以了解缺陷对载流子浓度和迁移率的影响。这项工作为我们提供了关于缺陷对赤铁矿中小极化子形成和输运性质的作用的基本理解，为新掺杂剂的设计提供了关键见解，以进一步提高过渡金属氧化物的太阳能-燃料转换效率。
Effect of Low Oxygen Annealing on Photoelectrochemical Water Splitting Properties of $α$-Fe$_2$O$_3$
光电化学（PEC）水分解是将太阳能转化为以氢的形式储存的化学能的有前途的方法。纳米结构的赤铁矿（$α$ $_2$ O $_3$）由于其大的比表面积和缩短到达表面所需的少数载流子扩散长度而成为用于高效载流子产生和收集的最有吸引力的材料之一。在本工作中，研究了通过在FTO玻璃上阳极化薄铁层并随后在仅具有0.03% O $_2$的低O $_2$ -Ar环境中退火制备的$α$ -Fe $_2$ O $_3$的PEC水裂解性能。关键的发现是，与经典的空气退火相比，在低氧浓度下退火阳极纳米结构提供了强烈增强的PEC性能。在1.5V vs. RHE下，前者的光电流为1.1mA/cm 2，是后者的11倍。在低氧气氛中退火的$α$ $_2$ O的PEC性能的增强可以归因于受控的形态、Sn掺杂和氧空位的引入，这有助于增强从光生位点到反应表面的空穴通量，并且另外导致在$α$ O $_3$和电解质之间的界面处增强的空穴转移。从所获得的结果可以明显看出，低氧退火是缺陷工程化和优化$α$ O $_3$电极以获得最大化PEC水裂解性能的令人惊讶的有效方法.
Rapid Atmospheric Vapor Deposition of H:In2O3 Transparent Conducting Oxide Thin Films
University of Oxford（牛津大学）；University of Surrey（萨里大学）；National Taiwan University（台湾大学）；University of Cambridge（剑桥大学）；University of Manchester（曼彻斯特大学）；Sungkyunkwan University（成均馆大学）；Univ. Toulouse, CNRS, Toulouse INP, LGC（图卢兹大学，法国国家科学研究中心，图卢兹第三工业大学，化学实验室）
Etching of elemental layers in oxide molecular beam epitaxy by O2-assisted formation and evaporation of their volatile suboxide: The examples of Ga and Ge
Surface Optimization of Superconducting Aluminum Resonators for Robust Quantum Device Fabrication
Fraunhofer Institut für Elektronische Mikrosysteme und Festkörpertechnologien EMFT（弗劳恩霍夫电子微系统和固态技术研究所）；Center Integrated Sensor Systems (SENS), Universität der Bundeswehr München（联邦国防大学慕尼黑集成传感器系统中心）
