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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]

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]