In this work, we report the crystalline structure, morphology, and optical properties of novel metastable hexagonal phase MoO3 (h-MoO3) nanobelts prepared by a simple hydrothermal route from peroxomolybdate solution with the presence of sodium nitrate as a mineralizer. During the reaction process, NaNO3 has been proposed to influence the deoxidation, condensation, and further dehydration of the water-soluble peroxomolybdate precursor for connecting the [MoO6] octahedra with vertex sharing and edge sharing arrangements on determining the generation of metastable phase. The present work comparatively investigates the photochromic and electrochromic behaviors of the resultant hexagonal h-MoO3 nanobelts and the common thermodynamically stable orthorhombic α-MoO3 nanobelts. The performances concerning photochromism on two types of MoO3 nanobelt suspensions show that the photochemical efficiency of h-MoO3 is more excellent than that of α-MoO3 under UV light irradiation based on a remarkable coloration phenomenon. And the as-obtained h-MoO3 nanobelt coated film exhibits a steady electrochromic property in quick response to electrical impulse. Higher structure openness degree in the tunnel structure of h-MoO3, which could lead to an efficient electron−hole separation and provid larger spatial locations for cation insertion/extraction and diffusion, is suggested to be responsible for its enhanced coloration properties.
In this work, we have successfully developed a mild solution-based route to elaborate well-aligned MoO 3 and MoO 2 nanorods as the electrode active materials directly on metallic current collectors for the first time. Prior to nanostructure growth, an incubation layer, containing peroxomolybdate precursors is deposited on the selected Cu foil, which has been found to play a crucial role on the oriented alignment of molybdenum oxide nanorods. The nanorod arrays are generated on the pretreated Cu substrate by initial heterogeneous nucleation and subsequent growth from an aqueous or ethanol solution of a peroxomolybdate precursor. A good electrical transport and interaction with nanorod-Cu metal contacts are revealed by the current-voltage characteristics in this work. While such molybdenum oxide array films adhering to copper foil were employed directly as an integrative working electrode, the capacitive behaviors indicate that both molybdenum oxide array electrodes possess high specific capacitance and excellent cycle retention for electrochemical supercapacitor applications, which are investigated in detail by cyclic voltammetry and galvanostatic charge-discharge measurements at different current densities. Such enhancements are predominantly attributed to the direct lengthways electronic pathways, increased effective surface area and low contact resistance between the aligned nanorods and the Cu current collector junctions.Scheme 1 A schematic representation of the expected advantages of integrative electrodes with 1D nanostructured active materials assembled on the metallic current collector.
The Lewis acid tris(pentafluorophenyl)borane was found to rapidly promote ring-opening β-hydride elimination in a 1,1′-bis(diphenylphosphino)ferrocene (dppf) nickelalactone complex under ambient conditions. The thermodynamic product of nickelalactone ring-opening was characterized as (dppf)Ni(CH(CH3)CO2BArf 3), the result of β-hydride elimination and subsequent 2,1-insertion from a transient nickel(II) acrylate hydride intermediate. Treatment of (dppf)Ni(CH(CH3)CO2BArf 3) with a nitrogen-containing base afforded a diphosphine nickel(0) η2-acryl borate adduct. Formation of the diphosphine nickel(0) η2-acryl borate adduct completes a net conversion of nickelalactone to acrylate species, a significant obstacle to catalytic acrylate production from CO2 and ethylene. Displacement of the η2-acrylate fragment from the nickel center was accomplished by addition of ethylene to yield a free acrylate salt and (dppf)Ni(CH2CH2).
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