123rliu

Electrode architecture: Intertwined titanium carbide MXene within a tangled polypyrrole nanowire matrix is prepared and demonstrated as a novel hybridization electrode with outstanding gravimetric capacitance (610 F g⁻¹) and stability (14 000 cycles) compared with reported MXene‐based supercapacitors (see figure).

Abstract

The exploration of the rational design and synthesis of unique and robust architectured electrodes for the high capacitance, rate capability, and stability of supercapacitors is crucial to the future of energy storage technology. Herein, an in situ synthesis of multilayered titanium carbide MXene tightly caging within a 3 D conducting tangled polypyrrole (PPy) nanowire (NW) network is proposed as an effective strategy to prevent the aggregation of MXene, profoundly enhancing the electrochemical performance of the supercapacitor. Owing to the beneficial effects of an ideal 3 D interconnected porous structure and high electrical conductivity, the obtained electrode exhibits fast charge and ion transport kinetics as well as full usage of active material. As expected, the 3 D Ti₃C₂T _x @PPY NW exhibits a specific capacitance five times higher than that of pristine MXene (610 F g⁻¹), a good rate capability up to a current density of 25 A g⁻¹, and excellent stability with 100 % retention after 14 000 cycles at 4 A g⁻¹, outperforming the known state‐of‐the‐art MXene‐based supercapacitor. Our work provides a facile method for enhancing the performance of MXene‐based energy storage devices.

Basic heteroarenes are a ubiquitous feature of pharmaceuticals and bioactive molecules, and Minisci-type additions of radical nucleophiles are a leading method for their elaboration. Despite many Minisci-type protocols that result in the formation of stereocenters, exerting control over the absolute stereochemistry at these centers remains an unmet challenge. We report a process for addition of prochiral radicals, generated from amino acid derivatives, to pyridines and quinolines. Our method offers excellent control of both enantioselectivity and regioselectivity. An enantiopure chiral Brønsted acid catalyst serves both to activate the substrate and induce asymmetry, while an iridium photocatalyst mediates the required electron transfer processes. We anticipate that this method will expedite access to enantioenriched small-molecule building blocks bearing versatile basic heterocycles.

Uncertainty surrounds agency as Oklahoma attorney general readies to take the helm

The direct synthesis of hydrogen peroxide (H2O2) from H2 and O2 represents a potentially atom-efficient alternative to the current industrial indirect process. We show that the addition of tin to palladium catalysts coupled with an appropriate heat treatment cycle switches off the sequential hydrogenation and decomposition reactions, enabling selectivities of >95% toward H2O2. This effect arises from a tin oxide surface layer that encapsulates small Pd-rich particles while leaving larger Pd-Sn alloy particles exposed. We show that this effect is a general feature for oxide-supported Pd catalysts containing an appropriate second metal oxide component, and we set out the design principles for producing high-selectivity Pd-based catalysts for direct H2O2 production that do not contain gold. Authors: Simon J. Freakley, Qian He, Jonathan H. Harrhy, Li Lu, David A. Crole, David J. Morgan, Edwin N. Ntainjua, Jennifer K. Edwards, Albert F. Carley, Albina Y. Borisevich, Christopher J. Kiely, Graham J. Hutchings

Abstract

Article

Structural properties have been a key factor that controls the electronic and magnetic behaviour at the interface of two oxide materials. Here the authors achieve a spatial control over these functional properties in oxides through the formation of octahedral superstructures in manganite superlattices.

Nature Communications doi: 10.1038/ncomms6710

Authors: E. J. Moon, R. Colby, Q. Wang, E. Karapetrova, C. M. Schlepütz, M. R. Fitzsimmons, S. J. May

Abstract

The mechanism of a common and highly versatile molecular coupling reaction is elucidated.

Authors: B. T. Worrell, J. A. Malik, V. V. Fokin

Journal of the American Chemical Society DOI: 10.1021/ja402058v