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Aqueous zinc-ion batteries (AZIBs) based on high-safety zinc metal anodes have advantages of low cost and high theoretical capacity and are considered as a promising large-scale energy storage system. Their practical application, however, is hampered by slow transport kinetics, low energy density, and poor cycling performance. In this work, we design and successfully synthesize ultrastable lattice water-rich VO2·xH2O materials by considering the fact that abundant crystallized water can act as "water lubrication", and a charge shielding medium to weaken the electrostatic effect. As a result, VO2·xH2O as a cathode for AZIBs can provide a specific capacity of 376 mA h g−1 after 200 cycles at 1 A g−1 and no apparent capacity decay after 8000 cycles at 15 A g−1. The excellent zinc storage performance can be ascribed to the efficient kinetics and abundant reaction sites of the VO2·xH2O electrode. A series of in situ and ex situ characterizations indicate that it is the H+/Zn2+ co-intercalation mechanism to store zinc in the VO2·xH2O electrode. In short, the abundant crystallized water vanadium-based materials may be excellent candidates for advanced cathode materials of AZIBs. [ABSTRACT FROM AUTHOR]

Organic electrodes have aroused growing interest by virtue of their molecular diversity, environmental friendliness, and operation safety. However, sluggish lithium diffusion kinetics, dissolution in the organic electrolyte, poor electrical conductivity and low reversible capacities are the bottlenecks compared to their inorganic counterparts. Herein, we report a new type of exfoliated covalent organic nanosheet (E-CON) based composite electrode with large reversible capacities for lithium organic batteries based on intriguing new lithium storage sites of C＝C and higher utilization efficiency of C＝N redox sites compared to its bulk counterpart. The surface modification of the E-CONs by carboxyl-functionalized graphene quantum dots (GQDs) and carbon nanotubes can ensure long cycle life of the electrode due to the facilitated transfer of charge or lithium and prevent restacking of E-CONs. The E-CON based composite electrode exhibits an extremely large reversible capacity of 1386 mA h g−1 (1687 mA h g−1 based on E-CON contribution in the composite) after 300 cycles at 100 mA g−1 with good high-rate capability. The lithium storage mechanism is determined to be one lithium ion per C＝N and two lithium ions per C＝C group from five hyper-conjugated benzene rings. [ABSTRACT FROM AUTHOR]

Designing highly active multifunctional catalysts to meet the demands for fuel cells, metal–air batteries, and water-splitting devices is a top priority. Here, an efficient and novel trifunctional electrocatalyst (Fe2P/Co@NPC) with Fe2P and Co nanoparticles embedded in porous carbon has been developed by facile one-pot pyrolysis. The synergistic effect of Fe2P and Co nanoparticles furnishes Fe2P/Co@NPC with excellent catalytic performance for oxygen reduction reaction (ORR, E1/2 = 0.876 V), oxygen evolution reaction (OER, η10 = 331 mV), and hydrogen evolution reaction (HER, η10 = 235 mV). Significantly, using Fe2P/Co@NPC catalyst as the cathode, the assembled anion exchange membrane fuel cell delivers a peak power density of 1.25 W cm−2. Moreover, the assembled rechargeable Zn–air battery, using Fe2P/Co@NPC as a bifunctional oxygen catalyst, exhibits a maximum power density of 233.56 mW cm−2 and impressive cycle performance. Using Fe2P/Co@NPC as a bifunctional HER and OER catalyst, the overall water electrolyzer also achieves a low voltage of 1.73 V to deliver 10 mA cm−2. This work represents a protocol for the preparation of high efficient trifunctional electrocatalysts using cheaper heteroatom-containing metal–organic small molecules as a precursor for electrochemical energy devices. [ABSTRACT FROM AUTHOR]

Sensing analysis is significantly important for human health and environmental safety, and has gained increasing concern. As a promising material, porous organic polymers (POPs) have drawn widespread attention due to the availability of plentiful building blocks and their tunable structures, porosity and functions. Moreover, the permanent porous nature could provide a micro-environment to interact with guest molecules, rendering POPs attractive for application in the sensing field. In this review, we give a comprehensive overview of POPs as a platform for sensing applications. POP-based sensors are mainly divided into five categories, including fluorescence turn-on sensors, fluorescence turn-off sensors, ratiometric fluorescent sensors, colorimetric sensors and chemiresistive sensors, and their various sensing applications in detecting explosives, metal ions, anions, small molecules, biological molecules, pH changes, enantiomers, latent fingerprints and thermosensation are summarized. The different structure-based POPs and their corresponding synthetic strategies as well as the related sensing mechanisms mainly including energy transfer, donor–acceptor electron transfer, absorption competition quenching and inner filter effect are also involved in the discussion. Finally, the future outlook and perspective are addressed briefly. [ABSTRACT FROM AUTHOR]

Transition metal carbides are promising anode candidates for lithium ion batteries, however, their potential accomplishment still requires a rational structural design to improve their low reversible capacities, especially at high current densities and during long-term cycling. This work designs ultrasmall MoC nanoparticles with a diameter of 2–3 nm that are anchored in a three-dimensional (3D) network of nitrogen-doped porous carbon (denoted as MoC–N–C). The MoC–N–C can not only shorten the ion diffusion pathway, leading to fast transport of Li+, but also accommodate the volume expansion and adhesion of MoC nanoparticles during long-term cycling. Consequently, it displays large charge reversible capacities of 1246 mA h g−1 (300 cycles, 100 mA g−1), 813 mA h g−1 (500 cycles, 1 A g−1) and 675 mA h g−1 (500 cycles, 2 A g−1), for lithium ion batteries. In addition to mesoporous properties, large surface area, high ion/electron conductivity, and N-doped characteristics, the excellent lithium storage capability of the MoC–N–C composites, especially at high current densities and during long-term cycling can be mainly ascribed to the significant pseudocapacitance contribution (∼84% at 0.5 mV s−1) and synergistic effects between the N-doped 3D conductive network and the in situ generated ultrafine MoC nanoparticles. [ABSTRACT FROM AUTHOR]