Abstract. CO oxidation on a clean Pt(111) single crystal and thin iron oxide films grown on Pt(111) was studied at different CO:O 2 ratios (between 1:5 and 5:1) and partial pressures up to 60 mbar at 400 -450 K. Structural characterization of the model catalysts was performed by scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy and temperature programmed desorption. It is found that monolayer FeO (111) films grown on Pt(111) are much more active than clean Pt(111) and nm-thick Fe 3 O 4 (111) films at all reaction conditions studied. Post-characterization of the catalysts revealed that at CO:O 2 >1 the FeO(111) film dewets the Pt surface with time, ultimately resulting in highly dispersed iron oxide particles on Pt(111). The film dewetting was monitored in situ by polarisation-modulated infrared reflection absorption spectroscopy. The reaction rate at 450 K exhibited first order for O 2 and non-monotonously depended on CO pressure. In O 2 -rich ambient the films were enriched with oxygen while maintaining the long range ordering.Based on the structure-reactivity relationships observed for the FeO/Pt films, we propose that the reaction proceeds through the formation of a well-ordered, oxygen-rich FeO x (1 < x < 2) film that reacts with CO through the redox mechanism. The reaction induced dewetting in fact deactivates the catalyst. The results may aid in our deeper understanding of reactivity of metal particles encapsulated by thin oxide films as a result of strong metal support interaction.

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Conductive hydrogels have become one of the most promising materials for skin-like sensors because of their excellent biocompatibility and mechanical flexibility. However, the limited stretchability, low toughness, and fatigue resistance lead to a narrow sensing region and insufficient durability of the hydrogelbased sensors. In this work, an extremely stretchable, highly tough, and anti-fatigue conductive nanocomposite hydrogel is prepared by integrating hydrophobic carbon nanotubes (CNTs) into hydrophobically associated polyacrylamide (HAPAAm) hydrogel. In this conductive hydrogel, amphiphilic sodium dodecyl sulfate was used to ensure uniform dispersion of CNTs in the hydrogel network, and hydrophobic interactions between the hydrogel matrix and the CNT surface formed, greatly improving the mechanical properties of the hydrogel. The obtained CNTs/HAPAAm hydrogel showed excellent stretchability (ca. 3000%), toughness (3.42 MJ m −3 ), and great anti-fatigue property. Moreover, it exhibits both high tensile strain sensitivity in the wide strain ranges (gauge factor = 4.32, up to 1000%) and high linear sensitivity (0.127 kPa −1 ) in a large-pressure region within 0−50 kPa. The CNTs/HAPAAm hydrogelbased sensors can sensitively and stably detect full-range human activities (e.g., elbow rotation, finger bending, swallowing motion, and pronouncing) and handwriting, demonstrating the CNTs/HAPAAm hydrogel's potential as the wearable strain and pressure sensors for flexible devices.

Thickness matters: Ultrathin oxide films on metals can greatly enhance catalytic activity, for example, in CO oxidation on an FeO(111) film grown on a Pt(111) substrate. Under the reaction conditions, the bilayer FeO film restructures to form a trilayer OFeO film (see picture). Experimental evidence for the structure/morphology of the film and theoretical modeling of the mechanism of its formation and CO oxidation on its surface are presented.

The morphology and thermal stability of Pt particles deposited on Fe 3 O 4 (111) films were studied by scanning tunneling microscopy (STM) and temperature programmed desorption of CO. Vacuum annealing at temperatures above 800 K led to significant Pt sintering that reduced CO uptake to a much higher extent than the Pt surface area. A similar effect on CO adsorption was observed after mild oxidation-reduction treatment at 500 K. The results are rationalized in terms of the strong metal-support interaction between Pt and Fe 3 O 4 , whereby the Pt particles were encapsulated by a FeO (111) monolayer film as shown by STM. The high adhesion energy between Pt and iron oxides derived from STM data is suggested to be the key factor for encapsulation.

Hydrogels based on supramolecular noncovalent interactions have attracted great research interest but are still limited by relatively low mechanical strength and performance deterioration at subzero temperatures because of the formation of ice crystallization. In this study, an antifreezing and mechanically strong gelatin supramolecular organohydrogel is prepared via a simple strategy of immersing a gelatin pre-hydrogel in the citrate (Cit) water/glycerol mixture solution. In the organohydrogel, a part of water molecules are replaced by glycerol, which inhibits the formation of ice crystallization even at extremely low temperature. In addition, the formation of noncovalent interactions such as the hydrophobic aggregation induced by the salting-out effect, ionic interactions between the −NH 3 + of gelatin and Cit 3− anions, and hydrogen bonding between gelatin chains and glycerol endows the organohydrogels with high mechanical strength and toughness. The supramolecular organohydrogel can maintain its mechanical flexibility even at −80 °C or be stored for a long time. Moreover, the nature of noncovalent interactions endows the organohydrogel with intriguing thermoplasticity, good healable ability, and excellent adhesive behavior at various substrate surfaces.

A green, fully recyclable and stretchable electronic sensor based on ionic conductive gelatin organohydrogels can operate at ultra-low temperature.

Günstige Lage: Ultradünne Oxidfilme auf Metallen können die katalytische Aktivität stark erhöhen, z. B. bei der CO‐Oxidation an einem FeO(111)‐Film auf Pt(111). Unter den Reaktionsbedingungen lagert sich der zweilagige FeO‐Film zu einem dreilagigen OFeO‐Film um (siehe Bild). Neben experimentellen Befunden zur Struktur und Morphologie des Films wird eine theoretische Modellierung des Filmbildungsmechanismus und der CO‐Oxidation auf der Oberfläche vorgestellt.