Excellent cycling stability and capability of novel mixed-metal vanadate coated with V2O5 materials in an aqueous solution

Cobalt-doped copper vanadate: a dual active electrocatalyst propelling efficient H2 evolution and glycerol oxidation in alkaline water

Strategically doped metal oxide nanomaterials signify a rapidly growing genre of functional materials with a wide range of practical applications. Copper vanadate (CuV) represents one such highly active system, which has been rarely explored following its doping with an abundant first-row transition metal. Here, we have developed a series of CuV samples with varying cobalt(ii) doping concentrations deploying a relatively simple solid state synthetic procedure. Among the samples, the 10% Co(ii)-doped CuV (Co_10%-CuV) exhibited excellent reactivity for both the H₂ evolution reaction (HER) and glycerol oxidation reaction (GOR) in an alkaline aqueous medium (pH 14.0) during cathodic and anodic scans, respectively. During this dual-active catalysis, surface-immobilized Co_10%-CuV operates at exceptionally low overpotentials of 176 mV and 160 mV for the HER and GOR, respectively, while achieving 10 mA cm² current density. The detailed spectroscopic analysis revealed the formation of formate as the major product during the GOR with a faradaic efficiency of >90%. Therefore, this Co_10%-CuV can be included on either side of a two-electrode electrolyzer assembly to trigger a complete biomass-driven H₂ production, establishing an ideal carbon-neutral energy harvest process.

Synthesis and Electrochemical Performance of KVO/GO Composites as Anodes for Aqueous Rechargeable Lithium-Ion Batteries

K_0.25V₂O₅ (KVO) and K_0.25V₂O₅/graphene oxide (KVO/GO) have been successfully synthesized by a chemical coprecipitation method and a subsequent calcination process. The structure and morphology of KVO and KVO/GO were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The as-obtained vanadate and vanadate modified by GO materials were used as anodes with LiMn₂O₄ as a cathode and saturated LiNO₃ as an electrolyte to assemble an aqueous rechargeable lithium-ion battery (ARLB). The cyclic voltammogram curves of both KVO and KVO/GO electrodes exhibited three pairs of redox peaks corresponding to charge/discharge platforms. We found that a small amount of graphene oxide added improved the electrochemical performance more significantly than excess graphene oxide. The as-prepared KVO/GO//LiMn₂O₄ could not only improve the initial discharge capacity but could also reduce the attenuation at a high current density. Furthermore, the ARLB with a KVO/GO anode exhibited an excellent rate performance and super long cycle life. These good electrochemical properties of this new ARLB system actually provided feasibility for application in large-scale power sources and energy storage devices.

Superior electrochemical performance of a novel LiFePO4/C/CNTs composite for aqueous rechargeable lithium-ion batteries

Olivine LiFePO₄ covered flocculent carbon layers wrapped with carbon nanotubes (CNTs) prepared by sol-gel method and calcination is used as the cathode material for aqueous rechargeable lithium-ion batteries (ARLBs). The phase structures and morphologies of the composite material are characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), and transmission electron microscopy (TEM). The mechanism and method through which CNTs and flocculent carbon improve the electrochemical performance are investigated in an aqueous lithium-ion battery by setting up a comparative experiment. The ARLB system is assembled using a LiFePO₄/C/CNTs cathode and a zinc anode in 1 mol L^-1 ZnSO₄·7H₂O and saturated LiNO₃ aqueous solution (pH = 6), which can deliver a capacity of 158 mA h g^-1 at a rate of 1C. Even at a rate of 50C, it still has a capacity of 110 mA h g^-1 after 250 cycles with fantastic capacity retention (95.7%). The lithium-ion diffusion coefficient increases by an order of magnitude due to the addition of CNTs together with flocculent carbon. Four LEDs are successfully powered by the ARLBs for more than one minute to demonstrate the practical application. The excellent rate capabilities and thrilling discharge capacity at a high rate indicate that this cathode material possesses excellent electrochemical performance, and this ARLB system exhibits excellent potential as a power source for environmental applications.