Solvothermal Synthesis of Medium-Entropy Oxide Spheres for Thermocatalytic Conversion of CO to Methanol.

New chemical compositions and structures for medium- and high-entropy oxides (HEOs) currently represent a promising new avenue in materials research for a wide range of applications including catalysis, energy storage, and ceramics. To speed up further development, synthesis methods for multicationic oxides are needed for controlling features like morphology, porosity, and chemical compositions. In this work, mesoporous spinel oxide spheres with five cations are synthesized using solvothermal synthesis techniques.

Quantifying the Hydration-Dependent Dynamics of Cu Migration and Activity in Zeolite Omega for the Partial Oxidation of Methane.

Copper-exchanged zeolite omega (Cu-omega) is a potent material for the selective conversion of methane-to-methanol (MtM) via the oxygen looping approach. However, its performance exhibits substantial variation depending on the operational conditions. Under an isothermal temperature regime, Cu-omega demonstrates subdued activity below 230 °C, but experiences a remarkable increase in activity at 290 °C.

Tuneable Short-Range Antiferromagnetic Correlation in Fe-Containing Entropy Stabilized Oxides.

To elucidate the impact of a high entropy elemental distribution of the lattice site on the magnetic properties in oxide compounds, a series of complex perovskites BaO ( = Y, Fe, Ti, Zr, Hf, Nb, and Ta) with different Fe content ratios (0, 0.2, 0.3, and 0.

Assessing the Productivity of the Direct Conversion of Methane-to-Methanol over Copper-Exchanged Zeolite Omega (MAZ) via Oxygen Looping.

The methane-to-methanol (MtM) conversion via the oxygen looping approach using copper-exchanged zeolites has been extensively studied over the last decade. While a lot of research has focussed on maximizing yield and selectivity, little has been directed toward productivity-a metric far more meaningful for evaluating industrial potential. Using copper-exchanged zeolite omega (Cu-omega), a material highly active and selective for the MtM conversion using the isothermal oxygen looping approach, we show that this material exhibits unprecedented potential for industrial valorization.

Synthesis and Characterization of High-Entropy Dawsonite-Type Structures.

High-entropy hydroxides are an emerging subcategory of high-entropy materials (HEMs), not only because they can serve as tailorable precursors to high-entropy oxides (HEOs) but also because they can have unique high-entropy properties themselves. Many hydroxide crystal structures that are important for various applications are yet to be studied within the context of high-entropy materials, and it is unknown if they can take a high-entropy form (typically five or more incorporated cations). One such material is the dawsonite-type structure, which is a material with applications in both catalysis and ceramics.

Hydrothermal synthesis of multi-cationic high-entropy layered double hydroxides.

High-entropy materials are compositionally complex materials which often contain five or more elements. The most commonly studied materials in this field are alloys and oxides, where their composition allows for tunable materials properties. High-entropy layered double hydroxides have been recently touted as the next focus for the field of high-entropy materials to expand into.

Copper-exchanged large-port and small-port mordenite (MOR) for methane-to-methanol conversion.

Zeolite mordenite (MOR) is one of the most studied zeolites for the stepwise direct conversion of methane to methanol, but it also can exist in two forms: large port and small port. Here we report that the synthesis and selection of the parent mordenite is critical for optimizing productivity, and that large-port mordenite outperforms small-port mordenite for the stepwise conversion of methane to methanol.

From Synthesis to Microstructure: Engineering the High-entropy Ceramic Materials of the Future.

Sintering and microstructural development in ceramics has long been studied in a two-dimensional grain size-density space, with only texture (i.e. deviation of grain orientation from random) used to gain first insights into additional parametric spaces.

Pinpointing and Quantifying the Aluminum Distribution in Zeolite Catalysts Using Anomalous Scattering at the Al Absorption Edge.

The location of aluminum in a zeolite framework structure defines the accessibility and geometry of the catalytically active sites, but determining this location crystallographically is fraught with difficulties. Typical zeolite catalysts contain only a small amount of aluminum, and the X-ray scattering factors for silicon and aluminum are very similar. To address this problem, we have exploited the properties of resonant X-ray powder diffraction across the Al K edge, where the aluminum scattering factor changes dramatically.

Undoped SnO as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis.

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO with a very high surface area (>130 m g) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPR-H, and XPS.

Unwanted effects of X-rays in surface grafted copper(ii) organometallics and copper exchanged zeolites, how they manifest, and what can be done about them.

Copper(ii) containing materials are widely studied for a very diverse array of applications from biology, through catalysis, to many other materials chemistry based applications. We show that, for grafted copper compounds at the surface of silica, and for the study of the selective conversion of methane to methanol using copper ion-exchanged zeolites, the application of focused X-ray beams for spectroscopic investigations is subject to significant challenges. We demonstrate how unwanted effects due to the X-rays manifest, which can prevent the study of certain types of reactive systems, and/or lead to the derivation of results that are not at all representative of the behavior of the materials in question.

Active sites and mechanisms in the direct conversion of methane to methanol using Cu in zeolitic hosts: a critical examination.

In this critical review we examine the current state of our knowledge in respect of the nature of the active sites in copper containing zeolites for the selective conversion of methane to methanol. We consider the varied experimental evidence arising from the application of X-ray diffraction, and vibrational, electronic, and X-ray spectroscopies that exist, along with the results of theory. We aim to establish both what is known regarding these elusive materials and how they function, and also where gaps in our knowledge still exist, and offer suggestions and strategies as to how these might be closed such that the rational design of more effective and efficient materials of this type for the selective conversion of methane might proceed further.

Comparative performance of Cu-zeolites in the isothermal conversion of methane to methanol.

The isothermal, low-temperature stepwise conversion of methane to methanol over copper-exchanged zeolites eliminates the time-consuming heating and cooling steps of the conventional high temperature activation approach. To better understand differences between the two approaches, a series of zeolites were screened, of which omega zeolite (MAZ) showed superior performance in both the isothermal and conventional approaches.

On the Mechanism Underlying the Direct Conversion of Methane to Methanol by Copper Hosted in Zeolites; Braiding Cu K-Edge XANES and Reactivity Studies.

The application and quantification of in situ copper K-edge X-ray absorption near-edge structure (XANES), when linked to independently made reactor-based studies of methanol production, result in a majority relation between the production of Cu and methanol from methane that complies with the expectations of a two-electron mechanism founded upon Cu/Cu redox couples.

Assessing the relative stability of copper oxide clusters as active sites of a CuMOR zeolite for methane to methanol conversion: size matters?

Copper-containing zeolites exhibit high activity in the direct partial oxidation of methane into methanol at relatively low temperatures. Di- and tricopper species have been proposed as active catalytic sites, with recent experimental evidence also suggesting the possibility of the formation of larger copper oxide species. Using density functional theory based global geometry optimization, we were able to identify a general trend of the copper oxide cluster stability increasing with size.