Our contribution demonstrates that rhodium, an element that has barely been reported as an active metal for selective dehydrogenation of alkanes becomes a very active, selective, and robust dehydrogenation catalyst when exposed to propane in the form of single atoms at the interface of a solid-supported, highly dynamic liquid Ga–Rh mixture. We demonstrate that the transition to a fully liquid supported alloy droplet at Ga/Rh ratios above 80, results in a drastic increase in catalyst activity with high propylene selectivity. The combining results from catalytic studies, X-ray photoelectron spectroscopy, IR-spectroscopy under reaction conditions, microscopy, and density-functional theory calculations, we obtained a comprehensive microscopy picture of the working principle of the Ga–Rh supported catalytically active liquid metal solution.

The chemical bulk reductive covalent functionalization of thin-layerb lack phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkylh alides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations;t he products showed higher functionalization degrees than those obtained by neutral routes.Since 2014, two-dimensional (2D) black phosphorus (BP) has attracted tremendous attention throughout the scientific community due to its high p-type charge carrier mobility and its tunable direct band gap. [1][2][3][4][5][6][7][8][9] In contrast to graphene,B P exhibits amarked puckering of the sp 3 structure,constituting atwo-dimensional s-only system, involving one lone electron pair at each Pa tom. Whereas its outstanding physical and materials properties have been intensively investigated, its chemistry remains almost unexplored. [10][11][12] Indeed, af irst series of noncovalent functionalization protocols has been reported, mainly focused on improving the intrinsic instability of BP against water and oxygen. [13][14][15][16][17] Beyond these approaches,t he covalent functionalization of the interface is one of the most promising routes for fine-tuning the chemical and physical properties of 2D nanomaterials. [18,19] In this sense,only afew recent reports on single-flake chemistry with diazonium salts, [20] and wet-chemistry on previously exfoliated flakes with nucleophiles [21][22][23] or carbon-free radicals [24] have been reported so far.This is probably due to the intrinsic low degree of reactivity of neutral BP towards these reactions and the difficulties associated with overcoming the huge van der Waals energy stored within aBPcrystal, thus blocking the direct functionalization of BP.A long this front, ab ulk wetchemical derivatization sequence remains to be found. Moreover, an unambiguous determination of the covalent binding and its influence in the chemical structure of the P-layers is required to systematically explore the characteristics of BP reactivity.To address these challenges we took advantage of the well-known reductive graphene chemistry using graphite intercalation compounds (GICs). [18,[25][26][27] As af irst success in this direction, we have recently reported the preparation of BP intercalation compounds (BPICs) with alkali metals (K and Na). [28] This paves the way for the exploration of the reductive route using activated negatively charged BP-ite nanosheets and electrophiles (E) as covalent reaction partners.Herein, we provide the first real proof for covalent binding in BP with alkyl halides using abattery of characterization techniques.F urthermore,d ensity functional theory (DFT) calculations were carried out to rationalize our results, providing adeep understanding of the covalent derivatization of BP.This thorough study reveals for the first time the lattice opening in BP,absent in graphene,which is a...

Supported catalytically active liquid metal solutions (SCALMS) have been receiving increasing attention recently. We investigated the oxidation behavior of macroscopic Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles supported on SiO 2 /Si(100) with low Rh content (<2.5 at %) by x-ray photoelectron spectroscopy in ultra-high vacuum and under near-ambient pressure conditions using different photon energies and also using transmission electron microscopy. The experiments are accompanied by computational studies on the Ga oxide/Rh-Ga interface and Rh-Ga intermetallic compounds. For both Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles, exposure to molecular oxygen leads to the formation of an oxide shell in which Rh is enriched. High-resolution transmission electron microscopy on the Rh-Ga nanoparticles confirms the formation of an approximately 4 nm thick gallium oxide film containing Rh. Based on ab-initio molecular dynamics and computational studies on the Ga 2 O 3 /Ga interface, it is concluded that Rh incorporation into the Ga 2 O 3 film occurs by substituting octahedrally coordinated Ga.

We have prepared model systems for Pt–Ga supported catalytically active liquid metal solutions (SCALMS) by physical vapor deposition of Pt and Ga onto highly oriented pyrolytic graphite (HOPG). Prior to metal deposition, the HOPG support was modified by Ar+ bombardment. In this work, we focus on the stability of the Pt–Ga deposits toward agglomeration, which is a critical challenge in application. Specifically, we study the behavior of the model catalysts in ultrahigh vacuum (UHV) and under near ambient pressure (NAP) conditions at different temperatures. We use CO as a probe molecule to examine changes in the surface composition of the Pt–Ga deposits by in situ infrared reflection absorption spectroscopy (IRAS). In specific, we combine IRAS and ex situ atomic force microscopy (AFM) to study changes induced by annealing. We find that sintering effects are strongly dependent on the thickness of the deposited Pt–Ga layers. Our data suggest that particle ripening leads to a separation of the system into disperse Pt-rich and large Ga-rich particles. In the NAP regime, we performed simultaneous measurements with polarization modulation IRAS (PM-IRAS) and near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The alloying of Pt and Ga is accompanied by a shift of Pt 4f and Ga 3d photoelectron lines to higher binding energies. Although partial oxidation of Ga is observed upon CO exposure at pressures in the millibar regime, PM-IRAS shows adsorbed CO at a frequency typical for Pt ensembles in a Ga matrix.

Eine chemisch-reduktive Volumen-Funktionalisierung von dünnlagigem schwarzem Phosphor (BP) wurde unter Verwendung von BP-Interkalationsverbindungen entwickelt. Durche ffektive reduktive Aktivierung wurde die kovalente Funktionalisierung des geladenen BP mit Alkylhalogeniden erreicht. Die kovalente Funktionalisierung wurde umfassend mit mehreren spektroskopischen Methoden sowie DFT-Rechnungen nachgewiesen;e sl iegt ein hçherer Funktionalisierungsgrad als bei neutralen Funktionalisierungsreaktionen vor. Seit2014hatderzweidimensionale(2D)schwarzePhosphor(BP) wegen seiner hohen p-Typ-Ladungsträgermobilitätu nd seiner modifizierbaren, direkten Bandlücke große Aufmerksamkeit auf sich gezogen. [1][2][3][4][5][6][7][8][9] Im Unterschied zu Graphen besteht BP aus gewellten Schichten, die ausschließlich aus einem 2D-s-System gebildet werden und in denen jedes P-Atom ein freies Elektronenpaar aufweist. Während seine bemerkenswerten physikalischen und Materialeigenschaften bereits intensiv untersucht wurden, bleibt seine Chemie nahezu unerforscht. [10][11][12] Mittlerweile wurde eine erste Reihe von Vorschriften zur nicht-kovalenten Funktionalisierung verçffentlicht, die hauptsächlich darauf abzielen, die Instabilitätv on BP gegen Wasser und Sauerstoff zu verbessern. [13][14][15][16][17] Abgesehen von diesen Ansätzen gilt die kovalente Funktionalisierung der Oberfläche als eines der vielversprechendsten Konzepte zur Modifizierung der chemischen und physikalischen Eigenschaften von 2D-Nanomaterialien. [18,19] In diesem Sinne wurden bisher nur wenige Arbeiten, wie die Funktionalisierung einzelner Flocken mit Diazoniumsalzen [20] oder die nasschemische Funktionalisierung von zuvor hergestellten Flocken mit Nukleophilen [21][22][23] sowie mit freien Kohlenstoffradikalen, [24] publiziert. Der Grund hierfürl iegt wahrscheinlich in der niedrigen Reaktivitätv on neutralem BP bei diesen Reaktionen. In diesem Zusammenhang wird die direkte kovalente Funktionalisierung oftmals verhindert, da die BP-Schichten durch eine hohe Va n-der-Waals-Energie zusammengehalten werden. Ausd iesem Grund muss eine effektive nasschemische Funktionalisierungssequenz erst noch gefunden werden. Eine eindeutige Bestimmung der kovalenten Bindung und ihres Einflusses auf die chemische Struktur der BP-Schichten ist zudem zur systematischen Untersuchung der Reaktivitätvon BP erforderlich.Wirh aben uns die bekannte reduktive Graphenchemie, die auf der Verwendung von Graphit-Interkalationsverbindungen (GICs) beruht, zunutze gemacht. [18,[25][26][27] Als ersten Erfolg in dieser Richtung haben wir 2017 die Herstellung von BP-Interkalationsverbindungen (BPICs) mit Alkalimetallen (K und Na) beschrieben. [28] Dies ebnet den Wegz ur Erforschung der reduktiven Route basierend auf der Nutzung von