A novel optical dual sensor based on a coaxial electrospinning method for simultaneous sensing of oxygen and ammonia.

The coaxial electrospinning method is widely used in a wide range of applications, including medical devices and sensing technology. This study proposes a novel optical dual sensor for simultaneous detection of oxygen (O2) and ammonia (NH3) based on coaxial electrospinning method to produce core-shell fiber membrane doped fluorescent dyes. The O2 (core) and NH3 (shell) sensitive dye membranes were successfully fabricated using coaxial electrospinning method by dissolving a polymer matrix, cellulose acetate (CA), with platinum (II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and Eosin-Y, respectively. The optical dual sensor was illuminated by an UV LED to monitor the intensity change and wavelength shift in the presence of selected analyte gases. The experimental data show that the sensitivities of optical dual sensor were found to be 6.4 and 3.2 for O2 and NH3, respectively. The response and recovery times of O2 and NH3 sensing probes were measured to be 12 s/29 s and 65 s/66 s, respectively. Also, when exposed to NH3 gas gradually from 0 to 500 ppm, the wavelength shift data of Eosin-Y was started at 569.5 nm, 573.9 nm, 578.4 nm, 579.4 nm, 580.8 nm, and 582.2 nm, respectively. In applications, the proposed optical dual sensor based on coaxial electrospinning method can detect O2 and NH3 gases simultaneously.

A highly stable δ-MnO2 cathode with superior electrochemical performance for rechargeable aqueous zinc ion batteries.

Recently, aqueous zinc ion batteries (AZIBs) have attracted significant attention owing to their high safety, low cost, and abundant raw materials. However, finding an affordable and stable cathode, which can reversibly store a substantial amount of Zn2+ ions without damaging the original crystal structure, is still a major challenge for the practical application of ZIBs. It has already been demonstrated that δ-MnO2 is a promising cathode for AZIBs owing to its layered structure and superior electrochemical performance; however, the reported results are still unsatisfactory (especially cyclability). Thus, using an oil bath method, we have fabricated a δ-MnO2 cathode that exhibits a unique mixed phase morphology of mostly spherical nanoparticles and a few nanorods. It is believed that some of the nanoparticles are agglomerated to form nanorods, which may eventually help to offer numerous active sites for Zn2+ diffusion, enhancing the electrolyte osmosis and the contact area between the electrode and electrolyte. The obtained cathode delivers a high reversible capacity of ∼204 mA h g-1 for the 100th cycle and ∼75 mA h g-1 over 1000 cycles at a high current density of 3000 mA g-1 with stable long-range cycling. Ex situ results indicate the mechanism of formation of ZnMn2O4 during discharge, followed by the evolution of the layered δ-MnO2 during charge.

Aqueous Rechargeable Zn/ZnO Battery Based on Deposition/Dissolution Chemistry.

Recently, a novel electrochemical regulation associated with a deposition/dissolution reaction on an electrode surface has been proven to show superiority in large-scale energy storage systems (ESSs). Hence, in the search for high-performance electrodes showcasing these novel regulations, we utilized a low-cost ZnO microsphere electrode to construct aqueous rechargeable batteries (ARBs) that supplied a harvestable and storable charge through electrochemical deposition/dissolution via a reversible manganese oxidation reaction (MOR)/manganese reduction reaction (MRR), respectively, induced by the inherent formation/dissolution of zinc basic sulfate in a mild aqueous electrolyte solution containing 2 M ZnSO4 and 0.2 M MnSO4.

In Situ Oriented Mn Deficient ZnMn2O4@C Nanoarchitecture for Durable Rechargeable Aqueous Zinc-Ion Batteries.

Manganese (Mn)-based cathode materials have garnered huge research interest for rechargeable aqueous zinc-ion batteries (AZIBs) due to the abundance and low cost of manganese and the plentiful advantages of manganese oxides including their different structures, wide range of phases, and various stoichiometries. A novel in situ generated Mn-deficient ZnMn2O4@C (Mn-d-ZMO@C) nanoarchitecture cathode material from self-assembly of ZnO-MnO@C for rechargeable AZIBs is reported. Analytical techniques confirm the porous and crystalline structure of ZnO-MnO@C and the in situ growth of Mn deficient ZnMn2O4@C. The Zn/Mn-d-ZMO@C cell displays a promising capacity of 194 mAh g-1 at a current density of 100 mA g-1 with 84% of capacity retained after 2000 cycles (at 3000 mA g-1 rate). The improved performance of this cathode originates from in situ orientation, porosity, and carbon coating. Additionally, first-principles calculations confirm the high electronic conductivity of Mn-d-ZMO@C cathode. Importantly, a good capacity retention (86%) is obtained with a year-old cell (after 150 cycles) at 100 mA g-1 current density. This study, therefore, indicates that the in situ grown Mn-d-ZMO@C nanoarchitecture cathode is a promising material to prepare a durable AZIB.

A new rechargeable battery based on a zinc anode and a NaV6O15 nanorod cathode.

We explore NaV6O15 (NVO) nanorod cathodes prepared by a sol-gel method for aqueous rechargeable zinc-ion battery applications for the first time. The NVO cathode delivers a high capacity of 427 mA h g-1 at 50 mA g-1 current density. Furthermore, based on the mass of the active materials, it exhibits a high energy density of 337 W h kg-1.

Pyrosynthesis of Na3 V2 (PO4 )3 @C Cathodes for Safe and Low-Cost Aqueous Hybrid Batteries.

Rechargeable hybrid aqueous batteries (ReHABs) have emerged as promising sustainable energy-storage devices because all components are environmentally benign and abundant. In this study, a carbon-wrapped sponge-like Na3 V2 (PO4 )3 nanoparticle (NVP@C) cathode is prepared by a simple pyrosynthesis for use in the ReHAB system with impressive rate capability and high cyclability. A high-resolution X-ray diffraction study confirmed the formation of pure Na ion superionic conductor (NASICON) NVP with rhombohedral structure. When tested in the ReHAB system, the NVP@C demonstrated high rate capability (66 mAh g-1 at 32 C) and remarkable cyclability over 1000 cycles (about 72 % of the initial capacity is retained at 30 C). Structural transformation and oxidation change studies of the electrode evaluated by using in situ synchrotron X-ray diffraction and ex situ X-ray photoelectron spectroscopy, respectively, confirmed the high reversibility of the NVP@C electrode in the ReHAB system through a two-phase reaction. The combined strategy of nanosizing and carbon-wrapping in the NVP particles is responsible for the remarkable electrochemical properties. The pyrosynthesis technique appears to be a promising and feasible approach to prepare a high-performance electrode for safe and low-cost ReHAB systems as nextgeneration large-scale energy storage devices.

Na2V6O16·3H2O Barnesite Nanorod: An Open Door to Display a Stable and High Energy for Aqueous Rechargeable Zn-Ion Batteries as Cathodes.

Owing to their safety and low cost, aqueous rechargeable Zn-ion batteries (ARZIBs) are currently more feasible for grid-scale applications, as compared to their alkali counterparts such as lithium- and sodium-ion batteries (LIBs and SIBs), for both aqueous and nonaqueous systems. However, the materials used in ARZIBs have a poor rate capability and inadequate cycle lifespan, serving as a major handicap for long-term storage applications. Here, we report vanadium-based Na2V6O16·3H2O nanorods employed as a positive electrode for ARZIBs, which display superior electrochemical Zn storage properties. A reversible Zn2+-ion (de)intercalation reaction describing the storage mechanism is revealed using the in situ synchrotron X-ray diffraction technique. This cathode material delivers a very high rate capability and high capacity retention of more than 80% over 1000 cycles, at a current rate of 40C (1C = 361 mA g-1). The battery offers a specific energy of 90 W h kg-1 at a specific power of 15.8 KW kg-1, enlightening the material advantages for an eco-friendly atmosphere.