Catalyst-free selective oxidation of C(sp3)-H bonds in toluene on water

The anisotropic water interfaces provide an environment to drive various chemical reactions not seen in bulk solutions. However, catalytic reactions by the aqueous interfaces are still in their infancy, with the emphasis being on the reaction rate acceleration on water. Here, we report that the oil-water interface activates and oxidizes C(sp3)-H bonds in toluene, yielding benzaldehyde with high selectivity (>99%) and conversion (>99%) under mild, catalyst-free conditions. Collision at the interface between oil-dissolved toluene and hydroxyl radicals spontaneously generated near the water-side interfaces is responsible for the unexpectedly high selectivity. Protrusion of free OH groups from interfacial water destabilizes the transition state of the OH-addition by forming π-hydrogen bonds with toluene, while the H-abstraction remains unchanged to effectively activate C(sp3)-H bonds. Moreover, the exposed free OH groups form hydrogen bonds with the produced benzaldehyde, suppressing it from being overoxidized. Our investigation shows that the oil-water interface has considerable promise for chemoselective redox reactions on water without any catalysts.

Passivating Lithiated Graphite via Targeted Repair of SEI to Inhibit Exothermic Reactions in Early-Stage of Thermal Runaway for Safer Lithium-Ion Batteries

The self-exothermic in early stage of thermal runaway (TR) is blasting-fuse for Li-ion battery safety issues. The exothermic reaction between lithiated graphite (LiC_x ) and electrolyte accounts for onset of this behavior. However, preventing the deleterious reaction still encounters hurdles. Here, we manage to inhibit this reaction by passivating LiC_x in real time via targeted repair of SEI. It is shown that 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (D₃ F) can be triggered by LiC_x to undergo ring-opening polymerization at elevated temperature, so as to targeted repair of fractured SEI. Due to the high thermal stability of polymerized D₃ F, exothermic reaction between LiC_x and electrolyte is inhibited. As a result, the self-exothermic and TR trigger temperatures of pouch cell are increased from 159.6 and 194.2 °C to 300.5 and 329.7 °C. This work opens up a new avenue for designing functional additives to block initial exothermal reaction and inhibit TR in early stage.

Boosting Catalytic Selectivity through a Precise Spatial Control of Catalysts at Pickering Droplet Interfaces

Exploration of new methodologies to tune catalytic selectivity is a long-sought goal in catalytic community. In this work, oil-water interfaces of Pickering emulsions are developed to effectively regulate catalytic selectivity of hydrogenation reactions, which was achieved via a precise control of the spatial distribution of metal nanoparticles at the droplet interfaces. It was found that Pd nanoparticles located in the inner interfacial layer of Pickering droplets exhibited a significantly enhanced selectivity for p-chloroaniline (up to 99.6%) in the hydrogenation of p-chloronitrobenzene in comparison to those in the outer interfacial layer (63.6%) in pure water (68.5%) or in pure organic solvents (46.8%). Experimental and theoretical investigations indicated that such a remarkable interfacial microregion-dependent catalytic selectivity was attributed to the microenvironments of the coexistence of water and organic solvent at the droplet interfaces, which could provide unique interfacial hydrogen-bonding interactions and solvation effects so as to alter the adsorption patterns of p-chloronitrobenzene and p-chloroaniline on the Pd nanoparticles, thereby avoiding the unwanted contact of C-Cl bonds with the metal surfaces. Our strategy of precise spatial control of catalysts at liquid-liquid interfaces and the unprecedented interfacial effect reported here not only provide new insights into the liquid-liquid interfacial reactions but also open an avenue to boost catalytic selectivity.

Electrode/electrolyte additives for practical sodium-ion batteries: a mini review

Problems of practical sodium-ion batteries.

Robust Chalcogenophene Viologens as Anolytes for Long-Life Aqueous Organic Redox Flow Batteries with High Battery Voltage

A series of chalcogenophene viologens ([(NPr)₂FV]Cl₄, [(NPr)₂TV]Cl₄, and [(NPr)₂SeV]Cl₄) as anolytes for neutral aqueous organic redox flow batteries (AORFBs) via a combination of chalcogenophenes (furan, thiophene, and selenophene) and viologens are reported. The chalcogenophene viologens showed narrow HOMO-LUMO energy gap, high solubility, and stable electrochemical properties. Compared with the parent [(NPr)₂V]Cl₄, the introduction of π-conjugated chalcogenophene groups reduced the redox potential and enhanced the stability of their free radical state, which endowed the chalcogenophene viologens/FcNCl-based AORFBs with a higher theoretical battery voltage of 1.20 V and enhanced stability for one-electron storage. In particular, the [(NPr)₂FV]Cl₄/FcNCl-based AORFB exhibited excellent long-cycle stability for 3000 cycles with 0.0006% capacity decay per cycle for one-electron storage and 300 cycles with 0.06% capacity decay per cycle for two-electron storage at a charge voltage of 1.9 V (1.42 V theoretical battery voltage). This work provided a new strategy for regulating the voltage and improving the performance of neutral AORFBs.