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Bonding dissimilar elements to provide synergistic effects is an effective way to improve the performance of metal catalysts. However, as the properties become more dissimilar, achieving synergistic effects effectively becomes more difficult due to phase separation. Here we describe a comprehensive study on how subnanoscale alloying is always effective for inter-elemental synergy. Thirty-six combinations of both bimetallic subnanoparticles (SNPs) and nanoparticles (NPs) were studied systematically using atomic-resolution imaging and catalyst benchmarking based on the hydrogen evolution reaction (HER). Results revealed that SNPs always produce greater synergistic effects than NPs, the greatest synergistic effect was found for the combination of Pt and Zr. The atomic-scale miscibility and the associated modulation of electronic states at the subnanoscale were much different from those at the nanoscale, which was observed by annular-dark-field scanning transmission electron microscopy (ADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively.

For exploitation of a new class of aromatic micelles, we synthesized a bent pentacene-based amphiphilic molecule through Diels-Alder reaction. The amphiphiles bearing two trimethylammonium tethers assemble into a spherical aromatic micelle, with an average core diameter of 1.5 nm, in water at room temperature. The new aromatic micelle efficiently encapsulates perylene bisimide (PBI) dyes and graphene nanosheets (GNS) in water. The encapsulated PBI dyes form a parallel stacked dimer, exhibiting characteristic absorption and emission bands. In addition, the encapsulated GNS are composed of few-layer graphene sheets with an average lateral size of ∼7 nm, as confirmed by Raman spectroscopy. The resultant, aqueous host-guest complexes are stable even after three weeks in water under ambient conditions.

In this paper we combine two operando methods, Raman spectroscopy and X-ray absorption spectroscopy (XAS), in order to probe reduced graphene-oxide supported tinIV oxide nanoparticles ( SnO 2 NPs @ rGO ) as they are being used to catalyse CO2 electroreduction. To achieve high reaction rates it is necessary to apply sufficiently cathodic electrode potentials. Under such conditions, however, not only CO2 is reduced electrochemically, but also the catalyst particles may be transformed from the initial SnIV state to SnII or, in an extreme case, to metallic Sn. While SnII species still favour CO2 electroreduction, yielding formate as a primary product, on metallic Sn CO2 reduction is disfavoured with respect to the competing hydrogen evolution reaction (HER). We show that operando XAS, a robust technique yielding information averaged over a large surface area and a relatively large thickness of the catalyst layer, is a very expedient method able to detect the reduction of SnO 2 NPs @ rGO to metallic Sn. XAS can thus be used to establish an optimum potential for the electroreduction in practical electrolysing cells. It takes, however, a complementary method offered by operando Raman spectroscopy, having greater sensitivity at the catalyst/electrolyte solution interface, to probe reduction intermediates such as the SnII state, which remain undetectable for ex situ methods. As it is shown in the paper, Raman spectroscopy may also find further use when investigating the recovery of catalyst particles following exposure to extreme reducing conditions.

Subnanoclusters were characterized by elaborated spectroscopic methods revealing distinctive natures of subnanomaterials., Subnanometric metal clusters exhibit anomalous catalytic activity, suggesting innovative applications as next-generation materials, although identifying and characterizing these subnanomaterials in atomic detail remains a substantial challenge because of the severely weak signal intensity for the conventional analytical methods. Here, we report a subnanosensitive vibrational technique established based on the surface-enhanced Raman spectroscopy, demonstrating the first-ever detailed vibrational characterization of subnanomaterials. Furthermore, combining with density functional theory calculations, we reveal that inherent surface structures of the tin oxide subnanoclusters determine the size-specific spectral and catalytic characteristics of these clusters. The high-sensitivity characterization methodology elaborated here can provide a comprehensive understanding of the chemical and structural natures of subnanomaterials, which facilitate the rational design of subnanomaterials on the atomic scale for practical applications, such as in catalysts, biosensors, and electronics.

Spherical atoms have the highest geometrical symmetry. Due to this symmetry, atomic orbitals are highly degenerate, leading to closed-shell stability and magnetism. No substances with greater degrees of degeneracy are known, due to geometrical limitations. We now propose that realistic magnesium, zinc, and cadmium clusters having a specific tetrahedral framework possess anomalous higher-fold degeneracies than spherical symmetry. Combining density functional theory calculations with simple tight-binding models, we demonstrate that these degeneracies can be attributed to dynamical symmetry. The degeneracy condition is fully identified as an elegant mathematical sequence involving interatomic parameters. The introduction of dynamical symmetry will lead to the discovery of a novel category of substances with super-degenerate orbitals.

Rh modified Au(111-25 nm) electrodes, prepared by electron beam evaporation and galvanostatic deposition, were employed to study adsorption and electro-oxidation of CO on Rh in 0.1 M sulfuric acid solution by in situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The results of ATR-SEIRAS experiments were compared with those obtained by infrared reflection absorption spectroscopy on three low-index Rh single crystal surfaces. The Rh film deposited on Au(111-25 nm) electrode consists of 3D clusters forming a highly stepped [n(111) × (111)]-like surface with narrow (111) terraces. When CO was dosed at the hydrogen adsorption potential region, CO adsorbed in both atop (COL) and bridge (COB) configurations, as well as coadsorbed water species, were detected on the Rh film electrode. A partial interconversion of spectroscopic bands due to the CO displacement from bridge to atop sites was found during the anodic potential scan, revealing that there is a potential-dependent preference of CO adsorption sites on Rh surfaces. Our data indicate that CO oxidation on Rh electrode surface in acidic media involves coadsorbed water and follows the nucleation and growth model of a Langmuir-Hinshelwood type reaction. The work was supported by the Research Center Jülich, the University of Bern, Swiss National Science Foundation (200020_144471, 200021-124643), the Spanish Ministerio de Economía y Competitividad (project CTQ2013-44083-P) and University of Alicante. QX acknowledges fellowships of the Research Center Jülich; IP acknowledges support by COST Action TD 1002; and AK acknowledges the financial support by CTI Swiss Competence Centers for Energy Research (SCCER Heat and Electricity Storage).

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g(-1) at a current density of 10 μA cm(-2) and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

A novel, low cost polymer electrolyte membrane for direct methanol fuel cell (DMFC) has been fabricated using the pore-filling technique with copolymer composed of poly-2-acrylamide-2-methylpropanesulphonic acid (PAMPS) and poly-styrene sulphonic acid (PSS) impregnated in a porous polyimide (PI) substrate. The pore-filling membranes, as well as a Nafion membrane as a reference, were subjected to proton conductivity, methanol permeability and DMFC performance tests at various methanol concentrations to understand the effect of ion-conductive copolymer component towards the DMFC applications. PAMPS–PSS pore-filling membranes showed a decrease in methanol permeability whilst they retained their proton conductivity, consequently improving the DMFC performance compared to commercial Nafion membrane. The steric and hydrophobic properties of PSS allow to improve methanol crossover, achieving high DMFC performance in methanol concentration up to 5 mol L−1, demonstrating that PAMPS–PSS pore-filling membranes are attractive for the DMFC applications.

The electrochemical reduction of CO(2) has been extensively studied over the past decades. Nevertheless, this topic has been tackled so far only by using a very fundamental approach and mostly by trying to improve kinetics and selectivities toward specific products in half-cell configurations and liquid-based electrolytes. The main drawback of this approach is that, due to the low solubility of CO(2) in water, the maximum CO(2) reduction current which could be drawn falls in the range of 0.01-0.02 A cm(-2). This is at least an order of magnitude lower current density than the requirement to make CO(2)-electrolysis a technically and economically feasible option for transformation of CO(2) into chemical feedstock or fuel thereby closing the CO(2) cycle. This work attempts to give a short overview on the status of electrochemical CO(2) reduction with respect to challenges at the electrolysis cell as well as at the catalyst level. We will critically discuss possible pathways to increase both operating current density and conversion efficiency in order to close the gap with established energy conversion technologies.

On Au(111) electrodes, the investigation of ClO4− adsorption is hampered by a simultaneous surface reconstruction. We demonstrate that these two processes can be decoupled in cyclic voltammograms by a proper choice of the scan rate and of the initial potential. Our approach allowed the establishment of a relation between potentials of zero charge for the reconstructed and unreconstructed Au(111) surfaces. Keywords: Au(111), Perchlorate adsorption, Surface reconstruction, pzc, SEIRAS

The bioelectrocatalytic (oxygen reduction reaction, ORR) properties of the multicopper oxidase CueO immobilized on gold electrodes were investigated. Macroscopic electrochemical techniques were combined with in situ scanning tunneling microscopy (STM) and surface-enhanced Raman spectroscopy at the ensemble and at the single-molecule level. Self-assembled monolayer of mercaptopropionic acid, cysteamine, and p-aminothiophenol were chosen as redox mediators. The highest ORR activity was observed for the protein attached to amino-terminated adlayers. In situ STM experiments revealed that the presence of oxygen causes distinct structure and electronic changes in the metallic centers of the enzyme, which determine the rate of intramolecular electron transfer and, consequently, affect the rate of electron tunneling through the protein. Complementary Raman spectroscopy experiments provided access for monitoring structural changes in the redox state of the type 1 copper center of the immobilized enzyme during the CueO-catalyzed oxygen reduction cycle. These results unequivocally demonstrate the existence of a direct electronic communication between the electrode substrate and the type 1 copper center. Financial support from the Spanish Ministerio de Ciencia e Innovacion (CTQ2010−18570) and Generalitat Valenciana (ACOMP/2013/073) is gratefully acknowledged. The work in Bern was supported by the European Union through the FP7 BacWire Project (Contract MNP4-SL-2009-229337), the CTIProject 13696.1 PFFLR-IV, and the University of Bern through a summer fellowship to V.C.

Interface engineering to attain a uniform and compact self-assembled monolayer at atomically flat surfaces plays a crucial role in the bottom-up fabrication of organic molecular devices. Here we report a promising and operationally simple approach for modification/functionalization not only at ultraflat single-crystal metal surfaces, M(111) (M=Au, Pt, Pd, Rh and Ir) but also at the highly oriented pyrolytic graphite surface, upon efficient in situ cleavage of trimethylsilyl end groups of the molecules. The obtained self-assembled monolayers are ultrastable within a wide potential window. The carbon–surface bonding on various substrates is confirmed by shell-isolated nanoparticle-enhanced Raman spectroscopy. Application of this strategy in tuning surface wettability is also demonstrated. The most valuable finding is that a combination of the desilylation with the click chemistry represents an efficient method for covalent and tailor-made functionalization of diverse surfaces., Formation of stable and uniform self-assembled monolayers on surfaces is a prerequisite for bottom-up fabrication of many organic molecular devices. Here, the authors present a fabrication approach based on desilylation chemistry for modification and functionalization on various metal and carbon surfaces.

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Room temperature molecular electronics get one step closer to reality by exploiting chemical contacts between a single molecule and graphite., An open challenge for single-molecule electronics is to find stable contacts at room temperature with a well-defined conductance. Common coinage metal electrodes pose fabrication and operational problems due to the high mobility of the surface atoms. We demonstrate how molecules covalently grafted onto mechanically robust graphite/graphene substrates overcome these limitations. To this aim, we explore the effect of the anchoring group chemistry on the charge transport properties of graphite-molecule contacts by means of the scanning tunneling microscopy break-junction technique and ab initio simulations. Molecules adsorbed on graphite only via van der Waals interactions have a conductance that decreases exponentially upon stretching the junctions, whereas the molecules bonded covalently to graphite have a single well-defined conductance and yield contacts of unprecedented stability at room temperature. Our results demonstrate a strong bias dependence of the single-molecule conductance, which varies over more than one order of magnitude even at low bias voltages, and show an opposite rectification behavior for covalent and noncovalent contacts. We demonstrate that this bias-dependent conductance and opposite rectification behavior is due to a novel effect caused by the nonconstant, highly dispersive density of states of graphite around the Fermi energy and that the direction of rectification is governed by the detailed nature of the molecule/graphite contact. Combined with the prospect of new functionalities due to a strongly bias-dependent conductance, these covalent contacts are ideal candidates for next-generation molecular electronic devices.