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Vanadium phosphates are established as the benchmark system for the selective oxidation of n‐butane towards maleic anhydride. By varying the phosphorus content on the surface of three V‐based catalysts with diverse performance, this study experimentally elaborates on the catalytic function of phosphorus. Contact time variation and cofeed studies revealed, that surface phosphates, deposited in sub‐monolayers via atomic layer deposition, significantly contribute to an increased product selectivity. Furthermore, our results suggest that the phosphorus particularly suppresses the consecutive combustion of the (re‐)adsorbed product. The recently introduced solid solution catalyst V1‐xNbxOPO4 with medium maleic anhydride selectivity could be tuned by the surface enrichment with phosphorus towards product selectivities of up to SMAN=60 %, under optimized alkane‐rich feed conditions. Therefore, POx‐V0.3Nb0.7OPO4 is introduced as promising catalyst, which is not based on vanadyl(IV) pyrophosphate, to access significantly higher MAN formation rates at increased alkane partial pressures of cn‐butane>10 %vol in n‐butane oxidation. [ABSTRACT FROM AUTHOR]

Ethanol is a high‐value chemical that can be produced from syngas derived from fossil or renewable resources. Silica‐supported catalysts based on Rh are reported to show the best performance so far. We report a comprehensive investigation for influence of catalyst composition on performance in syngas conversion to ethanol. We evaluate 53 different silica‐supported catalysts with a varying degree of Rh, Mn, Ir, Li and Ti, via high‐throughput testing. Correlation analysis reveals that Li and Ir tend to increase the selectivity to C2+ oxygenates, and catalysts with a 0.95 molar ratio of Rh : Mn show a tendency for high CO conversion. The composition 2.8Rh, 0.45Mn, 1.3Ir, 0.04Li, where the numbers indicate weight percentage, is identified to yield one of the highest C2+ oxygenate values reported in the literature so far. Moreover, combining this catalyst with a hydrogenation catalyst and converting C2+ oxygenates to ethanol, provides one of the highest ethanol yields reported so far in literature. [ABSTRACT FROM AUTHOR]

The direct conversion of synthesis gas could open up economically viable routes for the efficient production of ethanol. RhMn/SiO2 represents one of the most active systems reported thus far. Potential improvements were reported by added dopants, i.e., Ir, Ti, and Li. Yet, combining these elements leads to contradicting results, owing to the complexity of the interactions in a multi-promoted system. This complexity is often encountered in heterogeneous catalysis. We report a systematic data-driven approach for the assessment of complex multi-promoter interactions based on a combination of design-of-experiment, high-throughput experimentation, statistical analysis, and mechanistic assessment. We illustrate this approach for the system RhMn/SiO2 promoted with Ir, Li, and Ti. Using this approach, we investigate the impact of promoters' interactions on a mechanistic level. Our analysis depicts the means to learn hidden correlations in the performance data and, additionally, high performance for ethanol yield for the RhMnIr/SiO2 catalyst. The method presented outlines an efficient way to also elucidate co-promoter interactions in other complex environments. [ABSTRACT FROM AUTHOR]

Iron‐based catalysts are employed in CO2‐FTS due to their ability to convert CO2 into CO in a first step and their selectivity towards higher hydrocarbons in a second CO hydrogenation step. According to the literature, iron carbides represent the active phase for hydrocarbon formation and are claimed to emerge in the presence of CO. We propose nanostructured FeOx films as model systems to assess information about the complex phase transformations during CO2‐FTS. Mesoporous hematite, ferrihydrite, maghemite, maghemite/magnetite films were exposed to CO2‐FTS atmospheres at 20 bar and 300 °C. Up to three distinct phases were observed depending on the time‐on‐stream (TOS): a sintered maghemite/magnetite phase, a carbidic core‐shell structure, and a low‐crystalline, needle‐type oxide phase. Our findings indicate that the formation of an intermediary maghemite/magnetite phase, predominant after short TOS (30 h), precedes the evolution of the carbide phase. Yet, even after prolonged TOS (185 h), no full conversion into a bulk carbide is observed. [ABSTRACT FROM AUTHOR]

Porous thin layer materials are gaining importance in different fields of technology and pose a challenge to the accurate determination of materials' properties important for their function. Herein, a hybrid measurement technique using ellipsometry together with other independent methods for validation, is demonstrated. Ellipsometry provides information about the porosity of different mesoporous films (PtRuNP/OMC = 45%; IrOx = 46%) as well as about the pore size (pore radius of ≈5 nm for PtRuNP/OMC). In addition, the electronic structure of a material, such as intraband transitions of a mesoporous IrOx film, can be identified, which can be used to better understand the mechanisms of chemical processes. In addition, it is shown that ellipsometry can be used as a scalable imaging and visualization method for quality assurance in production. These require accurate and traceable measurements, with reference materials playing an important role that include porosity and other related properties. It is shown that novel analytical methods are useful for improving analytical work in this entire field. [ABSTRACT FROM AUTHOR]

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Alkali metal promoters have been widely employed for preparation of heterogeneous catalysts used in many industrially important reactions. However, the fundamentals of their effects are usually difficult to access. Herein, we unravel mechanistic and kinetic aspects of the role of alkali metals in CO2 hydrogenation over Fe‐based catalysts through state‐of‐the‐art characterization techniques, spatially resolved steady‐state and transient kinetic analyses. The promoters affect electronic properties of iron in iron carbides. These carbide characteristics determine catalyst ability to activate H2, CO and CO2. The Allen scale electronegativity of alkali metal promoter was successfully correlated with the rates of CO2 hydrogenation to higher hydrocarbons and CH4 as well as with the rate constants of individual steps of CO or CO2 activation. The derived knowledge can be valuable for designing and preparing catalysts applied in other reactions where such promoters are also used. [ABSTRACT FROM AUTHOR]

With the increasing production of renewable energy and concomitant depletion of fossil resources, the demand for efficient water splitting electrocatalysts continues to grow. Iridium (Ir) and iridium oxides (IrOx) are currently the most promising candidates for an efficient oxygen evolution reaction (OER) in acidic medium, which remains the bottleneck in water electrolysis. Yet, the extremely high costs for Ir hamper a widespread production of hydrogen (H2) on an industrial scale. Herein, the authors report a concept for the synthesis of electrode coatings with template‐controlled mesoporosity surface‐modified with highly active Ir species. The improved utilization of noble metal species relies on the synthesis of soft‐templated metal oxide supports and a subsequent shape‐conformal deposition of Ir species via atomic layer deposition (ALD) at two different reaction temperatures. The study reveals that a minimum Ir content in the mesoporous titania‐based support is mandatory to provide a sufficient electrical bulk conductivity. After ALD, a significantly enhanced OER activity results in dependency of the ALD cycle number and temperature. The most active developed electrocatalyst film achieves an outstanding mass‐specific activity of 2622 mA mgIr–1 at 1.60 VRHE in a rotating‐disc electrode (RDE) setup at 25 °C using 0.5 m H2SO4 as a supporting electrolyte. [ABSTRACT FROM AUTHOR]

State-of-the-art acidic oxygen evolution reaction catalysts are mainly based on mixed oxides of titanium and iridium or ruthenium. Because of its high chemical corrosion resistance and stability in acid, TiO 2 is a promising support material, yet with poor electrical conductivity. We herein theoretically examined the stability and the electronic properties of substituted rutile-phase titania, in which Ti is partly replaced by elements of the fourth, fifth and sixth period. For negative values of the calculated segregation energy, we conclude that the heteroelement M forms a solid solution for 25% or 50% substitution. For these heteroelements, we calculate the electrical conductivity. Since it is known that the electronic structure of transition metal oxides strongly depends on the applied theoretical method, we performed self-consistent optimizations of the Hartree-Fock contribution to the exchange functional in a hybrid functional for every compound. Experimentally, two favorable and two unfavorable elements were synthesized with 25% foreign metal concentration. The most promising candidates to improve the electronic properties of titania are Ta and Nb. [ABSTRACT FROM AUTHOR]

Metal carbides are promising materials for electrocatalytic reactions such as water electrolysis. However, for application in catalysis for the oxygen evolution reaction (OER), protection against oxidative corrosion, a high surface area with facile electrolyte access, and control over the exposed active surface sites are highly desirable. This study concerns a new method for the synthesis of porous tungsten carbide films with template‐controlled porosity that are surface‐modified with thin layers of nickel oxide (NiO) to obtain active and stable OER catalysts. The method relies on the synthesis of soft‐templated mesoporous tungsten oxide (mp. WOx) films, a pseudomorphic transformation into mesoporous tungsten carbide (mp. WCx), and a subsequent shape‐conformal deposition of finely dispersed NiO species by atomic layer deposition (ALD). As theoretically predicted by density functional theory (DFT) calculations, the highly conductive carbide support promotes the conversion of Ni2+ into Ni3+, leading to remarkably improved utilization of OER‐active sites in alkaline medium. The obtained Ni mass‐specific activity is about 280 times that of mesoporous NiOx (mp. NiOx) films. The NiO‐coated WCx catalyst achieves an outstanding mass‐specific activity of 1989 A gNi−1 in a rotating‐disc electrode (RDE) setup at 25 °C using 0.1 m KOH as the electrolyte. [ABSTRACT FROM AUTHOR]

Modern research methods produce large amounts of scientifically valuable data. Tools to process and analyze such data have advanced rapidly. Yet, access to large amounts of high‐quality data remains limited in many fields, including catalysis research. Implementing the concept of FAIR data (Findable, Accessible, Interoperable, Reusable) in the catalysis community would improve this situation dramatically. The German NFDI initiative (National Research Data Infrastructure) aims to create a unique research data infrastructure covering all scientific disciplines. One of the consortia, NFDI4Cat, proposes a concept that serves all aspects and fields of catalysis research. We present a perspective on the challenging path ahead. Starting out from the current state, research needs are identified. A vision for a integrating all research data along the catalysis value chain, from molecule to chemical process, is developed. Respective core development topics are discussed, including ontologies, metadata, required infrastructure, IP, and the embedding into research community. This Concept paper aims to inspire not only researchers in the catalysis field, but to spark similar efforts also in other disciplines and on an international level. [ABSTRACT FROM AUTHOR]

Theoretical calculations suggest a strong dependence of electrical conductivity and doping concentration in transition-metal doped titania. Herein, we present a combined theoretical and experimental approach for the prediction of relative phase stability and electrical conductivity in niobium-doped titania as model system. Our method paves the way towards the development of materials with improved electrical properties. [ABSTRACT FROM AUTHOR]

A method is described for analyzing the formation of nanoparticles via in situ SAXS and XANES by using synchrotron radiation. A mechanism of nanoparticle formation is described and the coalescence behavior of small nuclei is identified as essential factor in obtaining a narrow size distribution of formed particles.

The direct conversion of syngas to ethanol, typically using promoted Rh catalysts, is a cornerstone reaction in CO2 utilization and hydrogen storage technologies. A rational catalyst development requires a detailed structural understanding of the activated catalyst and the role of promoters in driving chemoselectivity. Herein, we report a comprehensive atomic‐scale study of metal–promoter interactions in silica‐supported Rh, Rh–Mn, and Rh–Mn–Fe catalysts by aberration‐corrected (AC) TEM. While the catalytic reaction leads to the formation of a Rh carbide phase in the Rh–Mn/SiO2 catalyst, the addition of Fe results in the formation of bimetallic Rh–Fe alloys, which further improves the selectivity and prevents the carbide formation. In all promoted catalysts, Mn is present as an oxide decorating the metal particles. Based on the atomic insight obtained, structural and electronic modifications induced by promoters are revealed and a basis for refined theoretical models is provided. [ABSTRACT FROM AUTHOR]

The first molecular carbonyl RhMn cluster Na2[Rh3Mn3(CO)18] 2 with highly labile CO ligands and predefined Rh‐Mn bonds could be realized and successfully used for the preparation of the silica (davisil)‐supported RhMnOx catalysts for the conversion of syngas (CO, H2) to ethanol (StE); it has been synthesized through the salt metathesis reaction of RhCl3 with Na[Mn(CO)5] 1 and isolated in 49 % yields. The dianionic Rh3Mn3 cluster core of 2 acts as a molecular single‐source precursor (SSP) for the low‐temperature preparation of selective high‐performance RhMnOx catalysts. Impregnation of 2 on silica (davisil) led to three different silica‐supported RhMnOx catalysts with dispersed Rh nanoparticles tightly surrounded by a MnOx matrix. By using this molecular SSP approach, Rh and MnOx are located in close proximity on the oxide support. Therefore, the number of tilted CO adsorption sites at the RhMnOx interface increased leading to a significant enhancement in selectivity and performance. Investigations on the spent catalysts after several hours time‐on‐stream revealed the influence of rhodium carbide RhCx formation on the long‐term stability. Catalysts Birth. The first carbonyl RhMn cluster Na2[Rh3Mn3(CO)18] has been synthesized, structurally characterized and utilized as well‐defined molecular single‐source precursor (SSP) for the low‐temperature preparation of selective high‐performance RhMn catalysts for the conversion of syngas to ethanol (StE). Highly dispersed Rh nanoparticles in a tightly surrounded MnOx matrix lead to a superior selectivity towards ethanol. [ABSTRACT FROM AUTHOR]

The complex microkinetics of the selective oxidation of n‐butane to maleic anhydride (MAN) over vanadyl pyrophosphate‐based (VPP) catalysts has been widely investigated so far, however, they are still under debate. We present novel results of kinetic analyses and isotope labeling to shed light on the activation of gas‐phase oxygen and the dynamics of oxygen species on the catalyst surface and in the bulk. We suggest the existence of at least two catalytically relevant surface oxygen species responsible for selective and unselective activation of n‐butane, which are formed by adsorption and consecutive dissociation of O2 at the active site. The formation of selective [O] from unselective [O2] is likely promoted by co‐fed H2O, which increases the MAN selectivity. Regarding the VPP bulk serving as a reservoir for active [O] species it is concluded that the dynamic exchange is limited to the amorphous surface layer forming under reaction conditions, whereas the crystalline bulk is not involved into the reaction. Labelling studies are heavily influenced by vital 16O/18O scrambling of MAN isotopes with the reaction product H2O. Good O, bad O: The activation of oxygen during the selective oxidation of n‐butane to maleic anhydride (MAN) over an industrial VPO catalyst was investigated with a focus on MAN selectivity and the influence of H2O, which lowers the formation rate of carbon oxides. [ABSTRACT FROM AUTHOR]

Abstract: The stabilization of crystal phases and nanostructured morphologies is an essential topic in application‐driven design of mesoporous materials. Many applications, e.g. catalysis, require high temperature and humidity. Typical metal oxides transform under such conditions from a metastable, low crystalline material into a thermodynamically more favorable form, i.e. from ferrihydrite into hematite in the case of iron oxide. The harsh conditions induce also a growth of the crystallites constituting pore walls, which results in sintering and finally collapse of the porous network. Herein, a new method to stabilize mesoporous templated metal oxides against sintering and pore collapse is reported. The method employs atomic layer deposition (ALD) to coat the internal mesopore surface with thin layers of either alumina or silica. The authors demonstrate that silica exerts a very strong influence: It shifts hematite formation from 400 to 600 °C and sintering of hematite from 600 to 900 °C. Differences between the stabilization via alumina and silica are rationalized by a different interaction strength between the ALD material and the ferrihydrite film. The presented approach allows to stabilize mesoporous thin films that require a high crystallization temperature, with submonolayer quantity of an ALD material, and to apply mesoporous materials for high temperature applications. [ABSTRACT FROM AUTHOR]