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Abstract: X-ray diffraction/scattering computed tomography (XRS-CT) was used to create two-dimensional images, with 20 μm resolution, of passivated Co/TiO2/Mn Fischer–Tropsch catalyst extrudates postreaction after 300 h on stream under industrially relevant conditions. This combination of scattering techniques provided insights into both the spatial variation of the different cobalt phases and the influence that increasing Mn loading has on this. It also demonstrated the presence of a wax coating throughout the extrudate and its capacity to preserve the Co/Mn species in their state in the reactor. Correlating these findings with catalytic performance highlights the crucial phases and active sites within Fischer–Tropsch catalysts required for understanding the tunability of the product distribution between saturated hydrocarbons or oxygenate and olefin products. In particular, a Mn loading of 3 wt % led to an optimum equilibrium between the amount of hexagonal close-packed Co and Co2C phases resulting in maximum oxygenate selectivity. XRS-CT revealed Co2C to be located on the extrudates’ periphery, while metallic Co phases were more prevalent toward the center, possibly due to a lower [CO] ratio there. Reduction at 450 °C of a 10 wt % Mn sample resulted in MnTiO3 formation, which inhibited carbide formation and alcohol selectivity. It is suggested that small MnO particles promote Co carburization by decreasing the CO dissociation barrier, and the Co2C phase promotes CO nondissociative adsorption leading to increased oxygenate selectivity. This study highlights the influence of Mn on the catalyst structure and function and the importance of studying catalysts under industrially relevant reaction times.

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Abstract: In layered lithium transition metal oxide cathodes, high-voltage operation is accompanied by the formation of oxygen dimers, which are widely used as an indicator of oxygen-redox activity. However, understanding the role that oxygen dimerization plays in facilitating charge compensation is still needed. Li2NiO3 (a 3d8L2-containing compound, where L is a ligand hole) is studied as a model system, where oxygen dimerization is shown to occur without cathode oxidation. Electrochemical cycling results in a net reduction of the cathode, accompanied by structural transformations, despite spectroscopic features of oxygen dimers arising at the top-of-charge. Here, oxygen dimerization is shown to coexist alongside a structurally transformed and electronically reduced cathode structure, thus highlighting that O dimerization is independent of bulk redox processes. This makes it clear that a thermodynamically derived transformation toward a reduced phase remains the only variable capable of generating O–O dimers in Li2NiO3.

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Abstract: In this work, a Suzuki cross-coupling procedure towards highly porous BINAP-based polymeric Ru-catalyst materials with tunable specific surface areas (SSAs) were synthesized and their stability towards reducing conditions was investigated. After removal of Pd impurities by an oxidative treatment with H2O2/HCl, the resulting catalysts were employed for the base-free ruthenium-catalyzed decomposition of aqueous formic acid to CO2 and H2 with TOFs of up to 134 000 h−1 and TONs up to 920 000.

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Abstract: he glass matrix of composition: 55SiO2–10B2O3–25Na2O-5BaO-5ZrO2 was incorporated with 10 to 40 wt% of UO3 by melt quenching technique. Neutron diffraction and Reverse Monte Carlo simulations revealed that the borosilicate network consists of SiO4, BO3 and BO4 units; upon adding 10 % UO3 the B-O coordination increases from 3.08 to 3.86 and subsequently decreases with a further in increase in UO3 content. X-ray absorption near edge and Extended X-ray absorption studies revealed that U exist in 5+ and 6+ oxidation states with U-O coordination numbers of 8 and 6 respectively. The thermal stability decreases and weight losses increases with the addition of UO3 in the glass matrix, the sample with 30 wt% UO3 has thermal stability comparable to that of matrix glass and exhibits lowest dissolution rate in water. Nanoindentation measurements showed that the microstructure of sample with 30 wt% UO3 is 11 % weaker than that of the matrix glass.

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Abstract: We present an experimental investigation of the magnetic ground state in Ba4⁢NbIr3⁢O12, a fractional valent trimer iridate. X-ray absorption and photoemission spectroscopy show that the Ir valence lies between 3+ and 4+ while Nb is pentavalent. Combined dc/ac magnetization, specific heat, and muon spin rotation/relaxation (µ⁢SR) measurements reveal no magnetic phase transition down to 0.05 K. Despite a significant Weiss temperature (ΘW∼−15 to −25 K) indicating antiferromagnetic correlations, a quantum spin-liquid (QSL) phase emerges and persists down to 0.1 K. This state likely arises from geometric frustration in the edge-sharing equilateral triangle Ir network. Our µ⁢SR analysis reveals a two-component depolarization, arising from the coexistence of rapidly (90%) and slowly (10%) fluctuating Ir moments. Powder x-ray diffraction and Ir-L3⁢edge x-ray absorption fine structure spectroscopy identify 8–10% Nb/Ir site-exchange, reducing frustration within part of the Ir network, and likely leading to the faster muon spin relaxation, while the structurally ordered Ir ions remain highly geometrically frustrated, giving rise to the rapidly spin-fluctuating QSL ground state. At low temperatures, the magnetic specific heat varies as 𝛾⁢𝑇+𝛼⁢𝑇2, indicating gapless spinon excitations, and possible Dirac QSL features with linear spinon dispersion, respectively.