GaPt nanocomposites are colloidally synthesized and purified using three washing procedures that directly affect the catalytic stability in propane dehydrogenation of supported catalytically active liquid metal solutions (SCALMS) fabricated thereof.

The redox interactions between transition metal oxides and sulfur‐containing compounds play a key role in catalytic processes and gas sensing technologies. In this study, we investigated the redox dynamics of Co 3 O 4 (111)/Ir(100) model catalysts in response to the adsorption and decomposition of hydrogen sulfide (H 2 S) using synchrotron radiation photoelectron spectroscopy. Upon adsorption at 300 K, H 2 S partially dissociates to form a mixture of SO 3 2− , S 2− , OH − , SH − , and chemisorbed H 2 S. Subsequent annealing in ultrahigh vacuum induces H 2 desorption below 400 K followed by desorption of H 2 S and H 2 O above 400 K. At temperatures exceeding 500 K, S 2− is progressively oxidized to SO 3 2− and subsequently to SO 4 2− . These transformations are accompanied by temperature‐dependent redox processes involving the Co 3 O 4 (111) surface: initial reduction upon formation of SO 3 2− species at 300 K, partial re‐oxidation upon H 2 desorption, and further reduction with H 2 O release. Above 550 K, annealing induces charge redistribution and lattice oxygen migration, leading to a more homogeneous stoichiometry of the Co 3 O 4 (111) film. This phenomenon reduces the redox response to chemical transformations at the surface. The obtained insights into H 2 S–Co 3 O 4 redox interactions provide a foundation for the rational design of cobalt oxide‐based catalytic gas sensors.

The inherent susceptibility of n-type organic semiconductors to molecular dioxygen (O2) results in electron trapping or in unintended p-doping, which in turn diminishes their electron mobility. This concept is challenged in the present study by exploring O2 interactions with organic charge-transfer complexes (CTCs), where electron donor-acceptor interactions generate partially delocalized electronic states. Using a CTC comprising a phenazine electron donor and a 7,7,8,8-tetracyanoquinodimethane (TCNQ) electron acceptor, we demonstrate that its exposure to O2 does not lead to electron extraction but instead enhances the charge-transfer activity. The increased electron density at the TCNQ acceptor upon CTC exposure to O2 is attributed to electron trap-states passivation by O2, without evidence of chemisorption. This passivation mitigates recombination losses, resulting in a threefold photoluminescence quantum yield increase, enhanced electrical conductivity, and improved charge-transfer state efficiency. Similar O2-mediated conductivity enhancements are observed across additional donor-acceptor pairs, proving the broader applicability of this effect, and paving the way for designing O2-enhanced advanced organic electronic materials.

The relationship between surface composition, oxidation state, and electrocatalytic activity is central to the knowledge-based design of efficient electrocatalysts. In this work, we employ a model electrochemistry approach combining the preparation and characterization of well-defined Ru(10-10) and Pt0.2Ru0.8/Ru(10-10) surfaces by synchrotron radiation photoelectron spectroscopy (SRPES), cyclic voltammetry (CV), and differential electrochemical mass spectrometry (DEMS). The combined study allowed us to establish the presence of adsorbed oxygen species on both surfaces after cycling to upper potential limits (UPLs) of 0.5 and 0.9 VRHE, the onset of surface oxidation at 1.1 VRHE, and formation of a RuO2 layer at 1.3 VRHE. We found that Pt-Ru surface alloying significantly enhances hydrogen evolution reaction (HER) activity compared to bare Ru(10-10); however, the effect of oxidation is strongly surface-dependent. Increasing the UPL promotes HER activity on Ru(10-10), consistent with a beneficial role of oxygen species. In contrast, HER activity on Pt0.2Ru0.8/Ru(10-10) decreases with increasing UPL up to 1.1 VRHE, indicating a detrimental effect of adsorbed oxygen, likely due to steric blocking or electronic modification of Pt-Ru active sites. At higher UPLs (1.3 VRHE), partial dealloying and the formation of ultrasmall Pt aggregates restore high HER activity. These findings identify a critical balance between oxidation and alloy structure in determining HER performance and highlight the importance of dynamic surface transformations in bimetallic catalysts.

The electronic metal support interaction (EMSI) plays a decisive role in determining the activity, selectivity, and stability of noble metal catalysts supported on reducible oxides. While EMSI can enhance catalytic performance, excessively strong charge transfer at the metal/oxide interface often leads to oxidation and disintegration of metal nanoparticles, particularly in systems such as Rh/Co3O4(111). In this work, we explore how bimetallic Rh-Pt interactions modulate and counteract EMSI at the Rh/Co3O4(111) interface. Two types of core-shell Rh-Pt nanoparticles with precisely controlled compositions and architectures were prepared on well-ordered Co3O4(111) thin films on an Ir(100) substrate and investigated using synchrotron radiation photoelectron spectroscopy. We found that incorporating Pt, either as the core in Pt@Rh or as the shell in Rh@Pt nanoparticles, significantly attenuates charge transfer, thereby stabilizing Rh in its metallic state and suppressing disintegration of the core@shell nanoparticles. This stabilization is attributed to strong Rh-Pt interaction and the ability of the two metals to form stoichiometric binary phases. These findings demonstrate that bimetallic interactions offer an effective strategy to tune EMSI, providing a fundamental basis for the design of electronically balanced and thermally stable catalysts supported on reducible oxides.

Monometallic Rh NPs supported on Co 3 O 4 (111) are susceptible to oxidation. Incorporating Pt to form Rh–Pt core–shell NPs reduces charge transfer at the metal/oxide interface, effectively preventing excessive oxidation and phase separation.

In this study, we conduct a comprehensive analysis of the energy storage and release of water-soluble 2,5-norbornadiene-2,3-dicarboxylic acid (DC-NBD) integrating spectroscopic characterization, pH-dependent speciation, and photochemical response analysis. We evaluate protonation and dimerization equilibria using potentiometric and 1H-NMR techniques, revealing three well-defined pH intervals that affect the reactivity and stability of the system. The photoinduced conversion of DC-NBD to DC-QC was investigated at different pH conditions, while the catalytic back-conversion of the most stable quadricyclane species (DC-QC2-) was evaluated on Au(111) and Pt(111) single-crystal surfaces by time-resolved photochemical infrared reflection absorption spectroscopy (PC-IRRAS) and density functional theory. Our findings demonstrate that photoisomerization and catalytic back-conversion can be efficiently conducted in an aqueous environment, eliminating the need for organic solvents. This study advances the development of water-soluble MOST systems, offering key insights into the molecular design and optimization of sustainable photoactive materials. Future research should focus on enhancing photochemical efficiency, improving long-term stability, searching for more active catalysts and scaling these systems for practical solar energy storage applications.

Commercially available Ru/Al2O3 catalysts were modified by thin film coating with ionic liquids (SCILL). While the uncoated Ru resulted in highly active, but non-selective catalysis, the SCILL systems were less active, but significantly more selective toward the intermediate methylcyclohexene. Reaction parameter studies included the variation of the metal loading, the type of ionic liquid, inorganic and organic additives in the ionic liquid film and the addition of methanol to the feed. The latter resulted in significant increase in methylcyclohexene selectivity, improving the yield by a factor of >70 from 0.1% (uncoated) to 7.5% (ionic liquid coated, methanol addition). The cooperative effect between ionic liquid coating and methanol addition is shown.

Electrocatalyst degradation, often caused by oxidative processes, forms a large barrier for the wide-spread application of electrolysers and fuel cells, which are crucial for a sustainable energy society. A detailed understanding of the catalyst surface structure under oxygen evolution reaction (OER) conditions is, therefore, required to design more stable catalysts. Here, we study the oxidation of a Pt(111) model electrode under operando conditions combining High-Energy Surface X-ray Diffraction (HE-SXRD) with a Rotating Disk Electrode (RDE) in a unique experimental setup. This approach allows us to follow the atomic structure of the electrode-electrolyte interface under oxygen evolution reaction conditions under hitherto unexplored potential regimes. We find that the Pt(111) surface gets electro-oxidized in a layer-by-layer fashion. From ex situ X-ray Reflectivity (XRR) and X-ray Photoelectron Spectroscopy (XPS) measurements we find that a sub-nm thick, PtO2 oxide film is forming, which deactivates the surface and leads to surface roughening. Our results provide important insights into the electrochemical oxidation of platinum electrocatalysts and resolves crucial differences to thermal oxidation processes.

Electrochemically active liquid organic hydrogen carriers (EC-LOHCs) present a promising strategy for sustainable energy storage and conversion. Among them, the isopropanol/acetone redox pair is particularly attractive, but selective electrochemical hydrogenation of acetone remains a key challenge. Here, we identify the active state of bimetallic Pt-Ru catalysts that enables unprecedented selectivity for isopropanol formation. This state consists of ultrasmall metallic Pt aggregates supported on a roughened Ru surface formed exclusively through electrochemical dealloying of Pt-Ru alloys. Structures with similar activity cannot be attained by vacuum-based deposition methods. Using cyclic voltammetry, synchrotron radiation photoelectron spectroscopy, electrochemical infrared reflection absorption spectroscopy, and differential electrochemical mass spectrometry, we establish a direct link between surface structure and product selectivity. The same active state also promotes isopropanol oxidation at low overpotential, enabling bidirectional catalysis. These findings uncover a previously unrecognized pathway to tune catalyst selectivity and lay the groundwork for reversible EC-LOHC systems that support efficient, closed-loop, and carbon-neutral energy technologies.

ZUSAMMENFASSUNG Die intrinsische Empfindlichkeit von organischen n‐Halbleitern gegenüber molekularem Sauerstoff (O 2 ) führt zu Elektroneneinfang oder zu unbeabsichtigter p‐Dotierung, welches wiederum die Elektronenmobilität verringert. Dieser Grundsatz wird mit der vorliegenden Studie herausgefordert, in der die Wechselwirkung von O 2 mit organischen Ladungstransferkomplexen (CTCs) untersucht wird, bei denen Elektronendonor‐Akzeptor‐Wechselwirkungen teilweise delokalisierte elektronische Zustände erzeugen. Am Beispiel eines CTCs aus Phenazin als Elektronendonor und TCNQ als Elektronenakzeptor wird aufgezeigt, dass die Zugabe von O 2 nicht zum Elektroneneinfang führt , sondern stattdessen die Ladungstransferaktivität verstärkt. Die erhöhte Elektronendichte am TCNQ‐Akzeptor bei Exposition des CTC mit O 2 wird auf die Passivierung der für den Elektroneneinfang verantwortlichen Defekte durch O 2 zurückgeführt, ohne dass Anzeichen für eine chemisorptive Wechselwirkung vorliegen. Diese Passivierung mindert Rekombinationsverluste, was zur Verdreifachung der Photolumineszenz‐Quantenausbeute, einer erhöhten elektrischen Leitfähigkeit und einer verbesserten Effizienz des Ladungstransferzustandes führt. Ähnliche O 2 ‐vermittelte Leitfähigkeitssteigerungen werden auch bei weiteren Donor‐Akzeptor‐Paaren beobachtet, was die breitere Anwendbarkeit dieses Effekts belegt und den Weg ebnet zur Entwicklung von verbesserten Materialien im Bereich organische Elektronik, deren Leistungsparameter durch O 2 erhöht werden.

The orthogonal self-assembly of anchored molecular monolayers on chemically heterogeneous substrates offers a route for bottom-up chemical nanopatterning and area-selective deposition. Herein, we investigated the selective growth of self-assembled monolayers (SAMs) of n-decanethiol (DT) and 4,4'-biphenyldicarboxylic acid (BPDCA) on a pristine Au(111) surface and on CoO nanoislands on Au(111) by physical vapor deposition (PVD) under ultrahigh vacuum (UHV) conditions. We combined in situ infrared reflection-absorption spectroscopy (IRAS) applied during PVD and scanning tunneling microscopy (STM). At 300 K, DT formed a lying-down phase on Au(111), which evolved into a denser and slightly more upright adlayer upon heating to 400 K. On the Au(111) surface partially covered by CoO nanoislands, BPDCA preferentially binds to CoO. BPDCA adopts a tilted or upright orientation on CoO with one carboxylate group bound to the surface and a free carboxylic acid group pointing towards the vacuum. When DT is dosed onto BPDCA-precovered CoO/Au(111), the BPDCA SAM is preserved while a DT SAM grows on the Au regions between the CoO islands. This observation demonstrates that the oxide-bound carboxylate layer is sufficiently robust to confine DT to the Au regions. Our results provide a vacuum-based procedure for orthogonal functionalization of a metal/oxide nanostructure to synthesize a nanopatterned SAM with different terminating functional groups.

Molecular solar thermal (MOST) systems, such as the norbornadiene/quadricyclane (NBD/QC) pair, combine solar energy conversion, storage, and release in a simple one-molecule process. The energy-releasing reaction QC to NBD can be controlled electrochemically. In this study, we used in-situ photoelectrochemical infrared spectroscopy (PEC-IRRAS) together with density functional theory (DFT) calculations to investigate how electron donating (EDG) and electron withdrawing (EWG) groups in the push-pull system of the MOST pair affect the electrocatalytic properties of the electrochemically triggered back-conversion. Specifically, we investigated cyano, tosyl, and methyl ester groups as EWGs, and methoxy, dimethylamine, thioether, and diphenylamine groups located in the para-position of a phenyl group as EDGs. We characterized the onset potential, electrochemical stability window, and selectivity. We found that these properties strongly depend on the strength of electron donation of the EDG, as it exclusively locates the highest occupied molecular orbital (HOMO) and raises its energy level. We obtained the highest selectivity for compounds with p-methoxyphenyl functionality.

Atomare Kontrolle über lösungsprozessierte hybride Halogenid‐Perowskite wird experimentell durch Atomlagenabscheidung aus der Lösung (Engl. solution atomic layer deposition , sALD) erreicht. Diese Methode überträgt die oberflächenchemischen Prinzipien der Gasphasen‐ALD (gALD) auf in der Flüssigphase gelöste Präkursoren. Durch das Umgehen der Einschränkungen, die mit der für die gALD nötige Flüchtigkeit der Präkursoren verbunden sind, erweitert die sALD das Spektrum nutzbarer Reaktions‐Chemien und zugänglicher Materialklassen. Wir demonstrieren ihre Anwendbarkeit für die Abscheidung ultradünner Filme ionischer Halbleiter, indem wir ein sALD‐Verfahren für den prominentesten Halogenid‐Perowskit, Methylammonium‐Triiodidoplumbat (CH 3 NH 3 PbI 3 , „MAPI“) entwickeln. Der Prozess zeigt bei Variation der Präkursordosierung ein sättigendes, selbstlimitierendes Wachstum, wie es für ALD typisch ist, was sowohl ex‐situ als auch in‐situ nachgewiesen wird. Die durch sALD abgeschiedenen MAPI‐Filme sind hochrein, stöchiometrisch und polykristallin. Werden MAPI‐Filme paarweise und in jeweils identischer Dicke durch sALD und durch ein modernes Spin‐Coating‐Verfahren hergestellt, so übertreffen die sALD‐Filme ihre Spin‐Coating Gegenstücke deutlich hinsichtlich der Ladungsträgerlebensdauer und der Stabilität. Sie weisen zudem eine hohe Ladungsträgermobilität auf und bilden funktionale lichtabsorbierende Schichten in Solarzellen.

Molecular solar thermal (MOST) systems combine the conversion, storage and release of solar energy using switchable photoisomers. Isomerization of azaborinines (BN-benzenes) to their Dewar isomers (BN-Dewar) yields BNB/BND couples, representing a relatively new class of MOST systems with promising properties for energy storage. However, so far only homogeneous catalysts are available for triggering energy release, which does not allow for a straightforward catalyst-photoisomer separation. In this work, we investigate the heterogeneously catalyzed energy release of two different BNB/BND-based MOST systems, namely 1-(tert-butyldimethylsilyl)-2-mesityl-1,2-dihydro-1,2-azaborinine/2-(tert-butyldimethylsilyl)-3-mesityl-2-aza-3-borabicyclo[2.2.0]hex-5-ene (BNB1/BND1) and 1-(tert-butyl)-2-mesityl-1,2-dihydro-1,2-azaborinine/2-(tert-butyl)-3-mesityl-2-aza-3-borabicyclo[2.2.0]hex-5-ene (BNB2/BND2), using Au(111) as a potential catalytic material. We used highly oriented pyrolytic graphite (HOPG) as inert reference surface. In our study, we combined photochemical infrared reflection absorption spectroscopy (PC-IRRAS) with density functional theory (DFT). We show that Au(111) is active in releasing the energy stored in a BNB/BND MOST system. However, the catalytic activity is strongly dependent on the substituents. Although the activity of the Au catalyst is too low to be implemented in applications, our study provides proof of principle that a heterogeneously catalyzed approach is applicable.

Atomic-level control of solution-processed hybrid halide perovskites is achieved experimentally by solution atomic layer deposition (sALD). This method transfers the surface chemical principles of gas-phase ALD (gALD) to precursors dissolved in the liquid phase. Circumventing limitations associated with precursor volatility, sALD broadens the portfolio of reaction chemistries usable and material classes accessible. We establish its applicability to depositing ultrathin films of ionic semiconductors by developing an sALD procedure for the most prominent halide perovskite, methylammonium triiodoplumbate (CH3NH3PbI3, 'MAPI'). The process saturates upon precursor dosage variation to self-limiting growth typical for ALD, as analyzed by ex-situ and in-situ techniques. sALD-deposited MAPI is highly pure, stoichiometric, and polycrystalline. When MAPI films are prepared in congruent pairs by sALD and by a state-of-the-art spin-coating method, sALD-grown films clearly outperform their spin-coated counterparts in terms of charge carrier lifetimes and stability. They exhibit high carrier mobility and yield functional light absorbing layers in solar cells.

Coating heterogeneous catalysts with ionic liquids (ILs), a strategy known as 'solid catalysts with ionic liquid layers', can fine-tune catalytic selectivity. Introducing functional groups into ILs enhances their interaction with reactants, but precise control over their positioning is crucial. The structural formation in the IL wetting layer of the carbonyl-functionalized IL [5-oxo-C6C1Im][NTf2] on Au(111) is investigated using infrared reflection absorption spectroscopy and scanning tunneling microscopy under ultrahigh vacuum conditions, supported by density functional theory and molecular dynamics simulations. At low temperatures (<130 K), the IL forms disordered islands, which coalesce into ordered films near ambient temperature. At low coverage, the IL adopts flat, space-demanding adsorption geometries. Upon forming a closed film, adsorption shifts to more compact configurations, with the carbonyl group tilting toward the vacuum while the ring remains surface-bound. Deposition at 300 K forms crystalline structures in the sub-monolayer regime, where the cation side chain can either stand upright or lie flat depending on the coverage. The IL remains thermally stable and desorbs completely at 500 K without decomposition. These findings highlight how IL coverage and deposition conditions tune functional group orientation at the catalyst interface, optimizing SCILL performance.

Recently, cobalt-based oxides have received considerable attention as an alternative to expensive and scarce iridium for catalyzing the oxygen evolution reaction (OER) under acidic conditions. Although the reported materials demonstrate promising durability, they are not entirely intact, calling for fundamental research efforts to understand the processes governing the degradation of such catalysts. To this end, this work studies the dissolution mechanism of a model Co3O4 porous catalyst under different electrochemical conditions using online inductively coupled plasma mass spectrometry (online ICP-MS), identical location scanning transmission electron microscopy (IL-STEM), and differential electrochemical mass spectrometry (DEMS). Despite the high thermodynamics tendency reflected in the Pourbaix diagram, it is shown that the cobalt dissolution kinetics is sluggish and can be lowered further by modifying the electrochemical protocol. For the latter, identified in this study, several (electro)chemical reaction pathways that lead to the dissolution of Co3O4 must be considered. Hence, this work uncovers the transient character of cobalt dissolution and provides valuable insights that can help to understand the promising stability of cobalt-based materials in already published works and facilitate the knowledge-driven design of novel, stable, abundant catalysts toward the OER in an acidic environment.

Atomic‐level control of solution‐processed hybrid halide perovskites is achieved experimentally by solution atomic layer deposition (sALD). This method transfers the surface chemical principles of gas‐phase ALD (gALD) to precursors dissolved in the liquid phase. Circumventing limitations associated with precursor volatility, sALD broadens the portfolio of reaction chemistries usable and material classes accessible. We establish its applicability to depositing ultrathin films of ionic semiconductors by developing an sALD procedure for the most prominent halide perovskite, methylammonium triiodoplumbate (CH 3 NH 3 PbI 3 , ‘MAPI‘). The process saturates upon precursor dosage variation to self‐limiting growth typical for ALD, as analyzed by ex‐situ and in‐situ techniques. sALD‐deposited MAPI is highly pure, stoichiometric, and polycrystalline. When MAPI films are prepared in congruent pairs by sALD and by a state‐of‐the‐art spin‐coating method, sALD‐grown films clearly outperform their spin‐coated counterparts in terms of charge carrier lifetimes and stability. They exhibit high carrier mobility and yield functional light absorbing layers in solar cells.