Explore the vast range of titles available.

The molecular approach to single-site and nanoparticle-based heterogeneous catalysts relies on a stringent control over the surface chemistry, enabled by the judicious choice of dehydroxylated supports and tailored organometallic precursors. Aided by the advanced characterization methods, the field of surface organometallic chemistry (SOMC) has provided molecular-level insights into the mechanism and the nature of active sites of various industrial catalysts. The development of SOMC over the last decades yielded supported catalysts outperforming their homogeneous precursors and provided design principles for catalyst development. Applying the rational structure-activity approach of homogeneous catalysis to the surface species leads to further advances of SOMC, including functional materials for sustainable chemistry, energy storage and imaging, to mention just a few. Graphical Abstract

For the first time, the pulse method has been applied to the study of the self-oscillatory behaviour. For methane oxidation over Ni foil the response to a sequence of equal pulses has been strictly periodic. The pulse method allowed to obtain some new information about the origin of oscillations in this reaction. Graphical Abstract

Inherent in the colloidal synthesis of nanoparticle catalysts is the presence of an organic capping agent that encapsulates the nanoparticles to prevent aggregation. However, this capping agent often remains present on the nanoparticles during catalytic reaction, and the effect of this coating on catalysis is an important question that will influence the future applications of colloidal nanoparticles. In this study, the structure of poly(vinylpyrrolidone) (PVP) ligands on Pt nanoparticles is probed using sum frequency generation vibrational spectroscopy before and after cap removal by UV light. When the PVP is removed, carbonaceous fragments remain on the surface that dynamically restructure in H 2 and O 2 . These fragments form a porous coating around the Pt in H 2 but collapse to a tightly closed shell in O 2 . Using ethylene hydrogenation and methanol oxidation as a probe for the catalytic activity of the nanoparticles in H 2 and O 2 , respectively, it is shown that the structure of these carbonaceous fragments controls the catalytic activity of the nanoparticles across several orders of magnitude by opening in H 2 and collapsing to block Pt sites in O 2 . Kinetic experiments on thermally-cleaned PVP-capped and oleic acid-capped nanoparticles show that these findings apply to multiple capping agents and cleaning methods. This work highlights the dominant role of an organic cap to mediate nanoparticle catalysis and provides one example where capped nanoparticles are dramatically better catalysts than their uncapped analogues. Graphical Abstract

Charge carrier separation is considered as a key factor in enhancing the photocatalytic process and can be maximized by mitigating surface recombination. Following this idea, the surface of zinc oxide (ZnO) was modified by thermal treatment and nickel oxide (NiO) deposition. The influence of the ZnO thermal treatment and NiO deposition conditions on the ZnO surface chemistry and heterostructure interface properties were investigated by in situ X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) and correlated to the dye photodegradation efficiency. The XPS analysis confirmed a change of doping of ZnO after thermal treatment, which mainly influenced the developed band bending, and has led to an improved photocatalytic activity. For the same reason, the heterostructures based on the surface cleaned ZnO surface had higher photocatalytic efficiency than the ones based on non-cleaned ZnO. The temperature input during NiO deposition had negligible effect on the heterostructure interface properties. The photocatalytic efficiency did not follow the band bending evolution because of a dominant contribution of charge recombination across the NiO layer as indicated by PL analysis. Graphical Abstract

Ionic liquids (ILs), salts with melting points below 100 °C, represent a fascinating class of liquid materials typically characterized by an extremely low vapor pressure. Besides their application as new solvents or as electrolytes for electrochemical purposes, there are two important concepts of using ILs in catalysis: Liquid–liquid biphasic catalysis and IL thin film catalysis. Liquid–liquid biphasic catalysis enables either a very efficient manner to apply catalytic ILs, e.g. in Friedel–Crafts reactions, or to apply ionic transition metal catalyst solutions. In both cases, phase separation after reaction allows an easy separation of reaction products and catalyst re-use. One problem of liquid–liquid biphasic catalysis is mass transfer limitation. If the chemical reaction is much faster than the liquid–liquid mass transfer the latter limits the overall reaction rate. This problem is overcome in IL thin film catalysis where diffusion pathways and thus the characteristic time of diffusion are short. Here, Supported Ionic Liquid Phase (SILP) and Solid Catalyst with Ionic Liquid Layer (SCILL) are the two most important concepts. In both, a high surface area solid substrate is covered with a thin IL film, which contains either a homogeneously dissolved transition metal complex for SILP, or which modifies catalytically active surface sites at the support for SCILL. In each concept, interface phenomena play a very important role: These may concern the interface of an IL phase with an organic phase in the case of liquid–liquid biphasic catalysis. For IL thin film catalysis, the interfaces of the IL with the gas phase and with catalytic nanoparticles and/or support materials are of critical importance. It has recently been demonstrated that these interfaces and also the bulk of ILs can be investigated in great detail using surface science studies, which greatly contributed to the fundamental understanding of the catalytic properties of ILs and supported IL materials. Exemplary results concerning the IL/vacuum or IL/gas interface, the solubility and surface enrichment of dissolved metal complexes, the IL/support interface and the in situ monitoring of chemical reactions in ILs are presented. Graphical Abstract Important concepts in catalysis with ionic liquids are reviewed, including Supported Ionic Liquid Phase (SILP) and Solid Catalyst with Ionic Liquid Layer (SCILL), along with the detailed analysis of the relevant interfaces using surface science methods.

We present a study in which the suitability of potassium promoted iron-based Fischer–Tropsch (FT) catalysts for the generation of synthetic natural gas additives via the hydrogenation of carbon dioxide through a combined reverse water gas shift (WGS) and FT reaction is studied. Using novel in situ instrumentation based on XRD and magnetometry techniques the reversible conversion of metallic iron to Hägg carbide under reaction conditions and its decomposition in hydrogen could be monitored. The facilitating effect of potassium in the formation of iron carbide could be exposed as function of time on stream. While the FT reaction was reduced in the presence of high potassium loadings the reverse WGS reaction seemed to be unperturbed. A faster activation of an iron phase obtained via the decomposition of iron carbide, compared to the initial activation of a pristine iron phase obtained via the reduction of iron oxide was witnessed. Graphical Abstract

During the last years it has been an increasing focus on fundamental studies of the Fischer–Tropsch synthesis (FTS). Steady-state isotopic transient kinetic analysis and first principles investigation have proven to be important methods in studying the reaction mechanism of FTS. The present contribution deals with recent progresses in understanding of the F–T mechanism on Co catalysts based on combined DFT calculations, in situ characterization, steady-state isotopic transient kinetic analysis and microkinetics. A brief outlook into future perspectives of the FTS for converting synthesis gas from different carbon sources to fuels and chemicals is also provided. Graphical Abstract

Surface science studies allow processes important for heterogeneous catalysis to be investigated in greatest detail. Starting from the simplest model of a catalytic surface, a metal single-crystal surface under ultrahigh vacuum conditions, enormous progress has been made in the last decades towards extending the surface science of catalysis to technically more relevant dimensions. In this perspective, we highlight recent work, including our own, dealing with the influence of water on metal-support interactions in surface science studies of oxide-supported metal nanoparticle model catalysts. In particular, the effect of hydroxyl groups on nucleation and sintering of metal nanoparticles, and surface science investigations into catalyst preparation using wet-chemical procedures are addressed. Graphical Abstract

Monodisperse Pt nanoparticles (NPs) with well-controlled sizes in the range between 1.5 and 10.8 nm, and shapes of octahedron, cube, truncated octahedron and spheres (~6 nm) were synthesized employing the polyol reduction strategy with polyvinylpyrrolidone (PVP) as the capping agent. We characterized the as-synthesized Pt nanoparticles using transmission electron microscopy (TEM), high resolution TEM, sum frequency generation vibrational spectroscopy (SFGVS) using ethylene/H 2 reaction as the surface probe, and the catalytic ethylene/H 2 reaction by means of measuring surface concentration of Pt. The nanoparticles were supported in mesoporous silica (SBA-15 or MCF-17), and their catalytic reactivity was evaluated for the methylcyclopentane (MCP)/H 2 ring opening/ring enlargement reaction using 10 torr MCP and 50 torr H 2 at temperatures between 160 and 300 °C. We found a strong correlation between the particle shape and the catalytic activity and product distribution for the MCP/H 2 reaction on Pt. At temperatures below 240 °C, 6.3 nm Pt octahedra yielded hexane, 6.2 nm Pt truncated octahedra and 5.2 nm Pt spheres produced 2-methylpentane. In contrast, 6.8 nm Pt cubes led to the formation of cracking products (i.e. C 1 –C 5 ) under similar conditions. We also detected a weak size dependence of the catalytic activity and selectivity for the MCP/H 2 reaction on Pt. 1.5 nm Pt particles produced 2-methylpentane for the whole temperature range studied and the larger Pt NPs produced mainly benzene at temperatures above 240 °C. Graphical abstract

Bending vibrations in the infrared spectra of ammonia adsorbed on Lewis acidic metal oxides, i.e., Al 2 O 3 , ZrO 2 and TiO 2 , and zeolite were analyzed with an aid of density functional theory (DFT) calculations. The results by DFT methods reveal the wavenumbers of the vibration modes ( ν 4 and ν 2 ) of NH 4 bonded to Brønsted acid site and the vibration modes ( δ s and δ d ) of NH 3 species coordinated to a Lewis acidic metal center (M = Al, Zr or Ti). The wavenumbers calculated based on DFT were reasonably in agreement with the experimentally observed values. The estimation of wavenumbers suggests that the δ s vibration of NH 3 hydrogen-bonded is invisible on a zeolite, because it is hidden by an intense absorption due to skeletal vibration. On the other hand, multiple bands of asymmetric bending modes ( δ d and ν 2 ) observed on a zeolite were assigned. A quantification method of Brønsted and Lewis acid sites, and hydrogen-bonded NH 3 is provided based on the peak assignments. Graphical Abstract Bending vibration bands in infrared (IR) spectra of ammonia adsorbed on Brønsted and Lewis acid sites, and hydrogen-bonded species were assigned with an aid of density functional theory.