Intrinsically Conductive Perovskite Oxides with Enhanced Stability and Electrocatalytic Activity for Oxygen Reduction Reactions

The oxygen reduction reaction (ORR) is traditionally catalyzed by carbon-supported precious metals, heteroatom-doped carbons, and transition-metal-carbon hybrids. Despite their good electric conductivity and high catalytic activities, these carbon-containing catalysts suffer from electrochemical carbon corrosion which limits their utility in metal-air batteries and fuel cells. Here, we report a class of perovskite La0.5Sr0.5Mn1-xNixO3-delta nanocrystals that are intrinsically conductive with good electrocatalytic activity for the ORR Among these perovskites, La0.5Sr0.5Mn1-xNixO3-delta (delta = 0.06, LSMN) exhibited the highest electrocatalytic activity for ORR with an onset potential of 1.02 V, a half-wave potential of 0.80-V, and a Tafel slope of -68 mV decade(-1) in 0.1 M potassium hydroxide aqueous solution. Negligible degradation of oxygen reduction currents was observed after 300 cyclic voltammetry scans from 1.08 to 0.15 V. We demonstrated that the electrically conductive perovskites with transition-metal redox couples and oxygen vacancies are essential. Our work demonstrates the possibility of carbon-free oxygen electrocatalysis with widely promising applications

Metallacyclic assembly of interlocked superstructures

Interlocked molecules are a type of supramolecules whose sub-components are held together not by covalent bonds but non-covalent interactions. Examples include rotaxanes, catenanes, Solomon links, ring-in-ring complexes, molecular Borromean rings, molecular knots and interlocked cages. The design and manufacture of these architectures is mainly based on self-assembly and template-directed methodologies. Inspired by the successful utilization of coordination-driven assembly in metallasupramolecular systems, the metallacyclic assembly of interlocked superstructures is developing rapidly and as such makes a fascinating topic for reviewing. In this review we will focus on the metal-directed synthesis of the different types of interlocked superstructures, as well as their functional applications. (C) 2016 Elsevier B.V. All rights reserved

A binary catalyst system of a cationic Ru–CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide

Binary catalyst systems comprising a cationic Ru-CNC pincer complex and an alkali metal salt were developed for selective hydro-boration of CO2 utilizing pinacolborane at r.t. and 1 atm CO2, with the combination of [Ru(CNCBn)(CO)(2)(H)][PF6] and (KOCO2Bu)-Bu-t producing formoxyborane in 76% yield. A bicyclic catalytic mechanism was proposed and discussed

Durable rechargeable zinc-air batteries with neutral electrolyte and manganese oxide catalyst

Neutral chloride-based electrolyte and directly grown manganese oxide on carbon paper are used as the electrolyte and air cathode respectively for rechargeable Zn-air batteries. Oxygen reduction and oxygen evolution reactions on manganese oxide show dependence of activities on the pH of the electrolyte. Zn-air batteries with chloride-based electrolyte and manganese oxide catalyst exhibit satisfactory voltage profile (discharge and charge voltage of 1 and 2 V at 1 mA cm(-2)) and excellent cycling stability (approximate to 90 days of continuous cycle test), which is attributed to the reduced carbon corrosion on the air cathode and decreased carbonation in neutral electrolyte. This work describes a robust electrolyte system that improves the cycle life of rechargeable Zn-air batteries. (C) 2016 Elsevier B.V. All rights reserved

A Robust Hybrid Zn-Battery with Ultralong Cycle Life

Advanced batteries with long cycle life and capable of harnessing more energies from multiple electrochemical reactions are both fundamentally interesting and practically attractive. Herein, we report a robust hybrid zinc battery that makes use of transition-metal-based redox reaction (M-O-OH -> M-O, M = Ni and Co) and oxygen reduction reaction (ORR) to deliver more electrochemical energies of comparably higher voltage with much longer cycle life. The hybrid battery was constructed using an integrated electrode of NiCo2O4 nanowire arrays grown on carbon-coated nickel foam, coupled with a zinc plate anode in alkaline electrolyte. Benefitted from the M-O/M-O-OH redox reactions and rich ORR active sites in NiCo2O4, the battery has concurrently exhibited high working voltage (by M-O-OH -> M-O) and high energy density (by ORR). The good oxygen evolution reaction (OER) activity of the electrode and the reversible M-O M-O-OH reactions also enabled smooth recharging of the batteries, leading to excellent cycling stabilities. Impressively, the hybrid batteries maintained highly stable charge-discharge voltage profile under various testing conditions, for example, almost no change was observed over 5000 cycles at a current density of 5 mA cm(-2) after some initial stabilization. With merits of higher working voltage, high energy density, and ultralong cycle life, such hybrid batteries promise high potential for practical applications

Nickel-Catalyzed Facile [2+2+2] Cyclotrimerization of Unactivated Internal Alkynes to Polysubstituted Benzenes

A catalytic [2+2+2] cyclotrimerization of unactivated internal alkynes providing cyclotrimerization products in excellent yields with high regioselectivity is described. The transformation is accomplished by using a simple catalytic mixture comprising Ni(acac)(2), an imidazolium salt and a Grignard reagent at room temperature or 60 degrees C for 20 min or 1 h

Photodriven single-crystal-to-single-crystal transformation

Molecular architectures containing photosensitive units respond to light, giving dramatic variations of their structure. In particular, the crystalline packing phases offer the possibility of significant advances in crystal design and the understanding of solid-state photoreactivity. In this review we mainly focus on three different photoreactivity patterns, namely the isomerization of azobenzene, open-ring closed-ring transformations of diarylethenes and cycloadditions of olefin pairs, as well as some examples of photoreactive crystals outside these types. Many interesting phototriggered functionalities are documented herein, such as photo-tuning of guest adsorption of azobenzene or diarylethene-based porous frameworks and crystalline organic polymers generated by photo-cycloaddition reactions taking place in the different networks. (C) 2016 Elsevier B.V. All rights reserved