O3 Nanowires Research Articles

New Y0.045Ni0.045Fe2.91O4 nanowires decorated over mesoporous silica for crystal violet removal: Response surface methodology optimization, kinetics, and isothermal studies

Recently, there has been considerable interest in developing an efficient, easily separable, cost-effective, and environmentally friendly catalyst for treating toxic environmental pollutants. In this study, we successfully designed yttrium–nickel-doped magnetite nanowires (Y0.045Ni0.045Fe2.91O4) and their mesoporous silica (MS)-coated composite (Y0.045Ni0.045Fe2.91O4/MS) using a simple coprecipitation method. The resulting composite demonstrated effective adsorption and photocatalytic degradation of crystal violet (CV) dye under sunlight. Various instrumental characterization techniques were employed to assess the nanowires' morphological, chemical, and surface functional properties and their composite. The existence of metal–oxygen bonds in Y0.045Ni0.045Fe2.91O4 within the 500–800 cm−1 range was verified through FTIR analysis. According to the Brunauer–Emmett–Teller analysis, the composite exhibited a surface area of 285 m2/g, a pore volume of 0.436 cm³/g, and an average pore width of 5 nm. The composite's high surface area and mesoporous nature underscored its porous structure, confirming its enhanced adsorption capacity for contaminants. High resolution XPS spectrum justified the presence of surface silanol groups (Si–OH) which are responsible for adsorption phenomena. Photocatalytic experiments revealed that Y0.045Ni0.045Fe2.91O4 nanowires and their composites achieved 89% and 90% degradation rates for CV dye within 60 and 10 min, respectively. The removal efficiency was assessed under optimized conditions of pH (8), dose (15 mg), time (60 and 10 min), and concentration (10 mg/L). Statistical analysis revealed that pH significantly impacted CV dye removal because functional group activation varied at different pH values. To elucidate the adsorption mechanism and kinetics, the Temkin isotherm model and pseudo-second-order kinetics model (R2 = 1.996 mg min−1) were the best fit for the composite. Furthermore, approximately 99% of the nanowires were magnetically separated from the reaction mixture in an external magnetic field. The demonstrated synergy of efficient adsorption–photocatalysis, coupled with easy recovery, suggests that innovatively designed nanomaterials are optimal for the water remediation of organic pollutants in wastewater.

Multiple synergies on cobalt-based spinel oxide nanowires for electrocatalytic oxygen evolution

Cobalt-based spinel oxides have excellent oxygen evolution reaction (OER) activities and are cheap to produce; however, they have limited commercial applications due to their poor electrical conductivities and weak stabilities. Herein, we soaked Co3-xNixO4 nanowires in NaBH4 solutions, which endowed Co3-xNixO4 with significant oxygen vacancy content and decorated BOx motifs outside the Co3-xNixO4 nanowires. X-ray photoelectron spectroscopy and in situ Raman data suggest that these evolutions improved the conductivity, hydrophilicity, and increased active sites of the spinel oxides, which synergistically boosted their overall OER performances. This improved performance made the optimized BOx-covered Co2.1Ni0.9O4 nanowires generate a current density of 10 mA cm−2 when used for the OER at an overpotential of only 307 mV, maintaining excellent stability at 50 mA cm−2 for 24 h. This study provides a facile method for designing cobalt-based spinel oxide OER catalysts.

Engineering Sub-Nanometer Hafnia-Based Ferroelectrics to Break the Scaling Relation for High-Efficiency Piezocatalytic Water Splitting.

Reversible control of ferroelectric polarization is essential to overcome the heterocatalytic kinetic limitation. This can be achieved by creating a surface with switchable electron density; however, owing to the rigidity of traditional ferroelectric oxides, achieving polarization reversal in piezocatalytic processes remains challenging. Herein, sub-nanometer-sized Hf0.5 Zr0.5 O2 (HZO) nanowires with a polymer-like flexibility are synthesized. Oxygen K-edge X-ray absorption spectroscopy and negative spherical aberration-corrected transmission electron microscopy reveal an orthorhombic (Pca21 ) ferroelectric phase of the HZO sub-nanometer wires (SNWs). The ferroelectric polarization of the flexible HZO SNWs can be easily switched by slight external vibration, resulting in dynamic modulation of the binding energy of adsorbates and thus breaking the "scaling relationship" during piezocatalysis. Consequently, the as-synthesized ultrathin HZO nanowires display superb water-splitting activity, with H2 production rate of 25687µmolg-1 h-1 under 40kHz ultrasonic vibration, which is 235and 41times higher than those of non-ferroelectric hafnium oxides and rigid BaTiO3 nanoparticles, respectively. More strikingly, the hydrogen production rates can reach 5.2µmolg-1 h-1 by addition of stirring exclusively.

3D-Printed Flexible PVDF-TrFE Composites with Aligned BCZT Nanowires and Interdigital Electrodes for Piezoelectric Nanogenerator Applications

Piezoelectric nanogenerators based on piezoelectric nanocomposites have attracted much interest in recent decades owing to their excellent piezoelectric properties and application in self-powered systems and wearable sensors. As a promising piezoelectric ceramic filler in composite-based generators, one-dimensional (1D) piezoelectric nanowires were filled into a polymer matrix to enhance its dielectric and piezoelectric properties. In this paper, flexible PVDF-TrFE composite films containing highly aligned Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) nanowires (NWs) have been manufactured via a direct-ink writing method. The effect of BCZT NW content on the dielectric, ferroelectric, and piezoelectric properties was investigated using multiphysics modeling and detailed experiments. An optimum composite composition was discovered, and the piezoelectric composite film with 15 wt % BCZT NWs possessed the highest energy harvesting figure of merit of 5.3 × 10–12 m2/N. Interdigital electrodes were combined with the composite to fabricate a patterned piezoelectric nanogenerator, where the piezoelectric nanogenerator can produce an open-circuit output voltage of 17 V, and the maximum output power density could reach 5.6 μW/cm2. This work provides opportunities for the optimization and fabrication of piezoelectric materials for energy-harvesting and sensing applications.

Selective Doping to Controllably Tailor Maximum Unit-Cell-Volume Change of Intercalating Li+ -Storage Materials: A Case Study of γ Phase Li3 VO4.

Capacity decay of an intercalating Li+‐storage material is mainly due to the its particle microcracks from stress‐causing volume change. To extend its cycle life, its unit‐cell‐volume change has to be minimized as much as possible. Here, based on a γ‐Li3VO4 model material, the authors explore selective doping as a general strategy to controllably tailor its maximum unit‐cell‐volume change, then clarify the relationship between its crystal‐structure openness and maximum unit‐cell‐volume change, and finally demonstrate the superiority of “zero‐strain” materials within 25–60 °C (especially at 60 °C). With increasing the large‐sized Ge4+ dopant, the unit‐cell volume of γ‐Li3+ x Ge x V1− x O4 becomes larger and its crystal structure becomes looser, resulting in the decrease of its maximum unit‐cell‐volume change. In contrast, the doping with small‐sized Si4+ shows a reverse trend. The tailoring reveals that γ‐Li3.09Ge0.09V0.91O4 owns the smallest maximum unit‐cell‐volume change of 0.016% in the research field of intercalating Li+‐storage materials. Consequently, γ‐Li3.09Ge0.09V0.91O4 nanowires exhibit excellent cycling stability at 25/60 °C with 94.8%/111.5% capacity‐retention percentages after 1800/1500 cycles at 2 A g−1. This material further shows large reversible capacities, proper working potentials, and high rate capability at both temperatures, fully demonstrating its great application potential in long‐life lithium‐ion batteries.

Flexoelectricity-Enhanced Photovoltaic Effect in Self-Polarized Flexible PZT Nanowire Array Devices.

In this investigation, we report the flexoelectricity-enhanced photovoltaic (FPV) effect in a flexible Pb(Zr0.52Ti0.48)O3 nanowire (PZT NW) array/PDMS (polydimethylsiloxane) nanocomposite. The simulation result of density functional theory (DFT) indicated that the FPV effect in PZT NWs can be greatly affected by the interactions of the strain gradients with the internal field generated by self-polarization. We found that when the nanocomposite film was curved down, the photovoltaic current of the aligned PZT-NW/PDMS composite increased by 84.6-fold and 27.6-fold compared with the PZT-nanoparticles/PDMS and randomly aligned PZT-NW/PDMS nanocomposites at the same curvature, respectively. This is mainly ascribed to the increased flexoelectricity in the aligned PZT-NW/PDMS nanocomposite. This study will contribute to a full understanding of the influence of nanoparticle shape on the flexophotovoltaic effect of nanocomposites. It will have potential use in nanocomposites for the study of the FPV effect and associated applications.

Magnetic Field Enhanced Electrocatalytic Oxygen Evolution of NiFe-LDH/Co3 O4 p-n Heterojunction Supported on Nickel Foam.

Here, a strategy to regulate the electron density distribution by integrating NiFe layered double hydroxides (NiFe-LDH) nanosheets with Co3 O4 nanowires to construct the NiFe-LDH/Co3 O4 p-n heterojunction supported on nickel foam (NiFe-LDH/Co3 O4 /NF) for electrocatalytic oxygen evolution reaction (OER) is proposed. The p-n heterojunction can induce the charge redistribution in the heterogeneous interface to reach Fermi level alignment, thus modifying the adsorption free energy of *OOH and improving the intrinsic activity of the catalyst. As a result, NiFe-LDH/Co3 O4 /NF exhibits outstanding OER performance with a low overpotential of 274mV at a current density of 50mAcm-2 and long-time stability over 90h. Moreover, NF can serve as a magnetic core that induces the exchange bias effect between the magnetic substrate and the active species under the action of the magnetic field, resulting in decreased magnetoresistance and weakened scattering of spin electrons, which further lowers the OER overpotential by 25mV @ 50mAcm-2 under a 10000G magnetic field. This work provides a new perspective on the design of p-n heterojunction catalysts and a deeper understanding of the magnetic field-enhanced electrocatalytic reactions.

Growth of Mn-Co-Ni-O nanowires by pulsed laser deposition

Manganese-cobalt–nickel oxides (Mn-Co-Ni-O) materials have been widely applied as infrared detectors due to its superior thermistor properties and one-dimensional Mn-Co-Ni-O nanowires are expected to significantly enhance the detecting performance. We herein present a novel approach for successfully growing Mn0.79Co1.71Ni0.50O4 nanowires with Au as catalyst by pulsed laser deposition. The influence of growth parameters on the morphology and structural properties of nanowires was explored, and the optimal growth condition of nanowires was obtained. The growth mechanism of Mn-Co-Ni-O nanostructures under different oxygen partial pressure environments is discussed. The deep understanding of the underlying growth mechanism can stimulate more future research on fabrication of high-quality Mn-Co-Ni-O nanowires.

Hierarchical Cu0.92Co2.08O4@NiCo-layered double hydroxide nanoarchitecture for asymmetric flexible storage device

As an efficient and environmentally friendly energy storage device, the practical application of supercapacitor is largely limited by the low energy density. Therefore, to design desiring electrode materials is very important in improving the performance of supercapacitor. In this work, we prepare NiCo-layered double hydroxides (NiCo–LDH) nanosheet arrays grown uniformly on Cu0.92Co2.08O4 (CCO) nanowires by a two-step solvothermal route. The heterogeneous core-shell structure consists of high conductive shell and high capacitive core. It can slow down the agglomeration of NiCo–LDH nanosheets and improve the conductivity of material. It also facilitates ion diffusion and faradaic redox reaction, thus enhances the electrochemical performance. CCO@NiCo–LDH sample delivers a specific capacity of 1652 F g−1 at 1 A g−1 and still 124 F g−1 at 10 g−1. A flexible asymmetric supercapacitor is assembled using the synthesized product as cathode. It presents an energy density of 42.38 Wh kg−1 at 1350 W kg−1.

Wide Dynamic Range Thermometer Based on Luminescent Optical Cavities in Ga2 O3 :Cr Nanowires.

Remote temperature sensing at the micro- and nanoscale is key in fields such as photonics, electronics, energy, or biomedicine, with optical properties being one of the most used transducing mechanisms for such sensors. Ga2 O3 presents very high chemical and thermal stability, as well as high radiation resistance, becoming of great interest to be used under extreme conditions, for example, electrical and/or optical high-power devices and harsh environments. In this work, a luminescent and interferometric thermometer is proposed based on Fabry-Perot (FP) optical microcavities built on Cr-doped Ga2 O3 nanowires. It combines the optical features of the Cr3+ -related luminescence, greatly sensitive to temperature, and spatial confinement of light, which results in strong FP resonances within the Cr3+ broad band. While the chromium-related R lines energy shifts are adequate for low-temperature sensing, FP resonances extend the sensing range to high temperatures with excellent sensitivity. This thermometry system achieves micron-range spatial resolution, temperature precision of around 1 K, and a wide operational range, demonstrating to work at least in the 150-550 K temperature range. Besides, the temperature-dependent anisotropic refractive index and thermo-optic coefficient of this oxide have been further characterized by comparison to experimental, analytical, and finite-difference time-domain simulationresults.

Electronic structure regulation and electrocatalytic mechanism of one-dimensional mesoporous La0.8Sr0.2Mn1-xCoxO3 with bifunctional electrocatalysts towards Zn-air batteries

The bimetallic perovskite oxides with outstanding bifunctional catalytic activity and stability are successfully prepared to accelerate multi-electron oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) via molten salt template method. The as-synthesized La0.8Sr0.2Mn0.95Co0.05O3 nanowires exhibit high specific surface area of 27.96 m2 g−1, higher than the most of perovskite oxides synthesized by other researchers. The Co dopants can effectively regulate the electronic structure of perovskites. The one-dimensional mesoporous La0.8Sr0.2Mn0.95Co0.05O3 exhibits excellent bifunctional catalytic activity on account of low ORR overpotential of 435 mV, OER overpotential of 439 mV, and the outstanding battery performance (peak power density of 150.72 mW cm−2 and 177 discharge-charge cycles). More importantly, density functional theory (DFT) calculation demonstrates that the enhanced ORR and OER electrocatalytic mechanism of La0.8Sr0.2Mn1-xCoxO3 originates from the regulated electronic structure with the most positive band center of O 2p, Mn 3d and Co 3d because of Co dopants.

O2-Type Li0.78[Li0.24Mn0.76]O2 Nanowires for High-Performance Lithium-Ion Battery Cathode.

Continued improvement in the electrochemical performance of Li-Mn-O oxide cathode materials is key to achieving advanced low-cost Li-ion batteries with high energy densities. In this study, O2-type Li0.78[Li0.24Mn0.76]O2 nanowires were synthesized by a solvothermal reaction to produce P2-type Na5/6[Li1/4Mn3/4]O2 nanowires, which were then subjected to molten salt Li-ion exchange. The resulting nanowires have diameters less than 20 nm and lengths of several micrometers. The full-Mn-based nanowires cathode material delivers a reversible capacity of 275 mAh g-1 at 0.1 C and 200 mAh g-1 at a high current rate of 15 C with a capacity retention of more than 80% and the voltage decay was dramatically suppressed after 100 cycles. This excellent performance is ascribed to the highly stable oxygen redox reaction and lack of layered-to-spinel phase transition in the O2-type structure during cycling.

Constructing Co3 O4 Nanowires on Carbon Fiber Film as a Lithiophilic Host for Stable Lithium Metal Anodes.

Lithium metal has been considered as the most promising anode electrode for substantially improving the energy density of next-generation energy storage devices. However, uncontrollable lithium dendrite growth, an unstable solid electrolyte interface (SEI), and infinite volume variation severely shortens its service lifespan and causes safety hazards, thus hindering the practical application of lithium metal electrodes. Here, carbon fiber film (CFF) modified by lithiophilic Co3 O4 nanowires (denoted as Co3 O4 Nws) was proposed as a matrix for prestoring lithium metal through a thermal infusion method. The homogeneous needle-like Co3 O4 nanowires can effectively promote molten lithium to infiltrate into the CFF skeleton. The post-formed Co-Li2 O nanowires produced by the reaction of Co3 O4 Nws and molten lithium can homogeneously distribute lithium ions flux and efficaciously increase the adsorption energy with lithium ions proved by density functional theory (DFT) calculation, boosting a uniform lithium deposition without dendrite growth. Therefore, the obtained composite anode (denoted as CFF/Co-Li2 O@Li) exhibits superior electrochemical performance with high stripping/plating capacities of 3 mAh cm-2 and 5 mAh cm-2 over long-term cycles in symmetrical batteries. Moreover, in comparison with bare lithium anode, superior Coulombic efficiencies coupled with copper collector and full battery behaviors paired with LiFePO4 cathode are achieved when CFF/Co-Li2 O@Li composite anode was employed.

Symmetry-Reduction Enhanced Polarization-Sensitive Photodetection in Core-Shell SbI3 /Sb2 O3 van der Waals Heterostructure.

Structural symmetry is a simple way to quantify the anisotropic properties of materials toward unique device applications including anisotropic transportation and polarization-sensitive photodetection. The enhancement of anisotropy can be achieved by artificial symmetry-reduction design. A core-shell SbI3 /Sb2 O3 nanowire, a heterostructure bonded by van der Waals forces, is introduced as an example of enhancing the performance of polarization-sensitive photodetectors via symmetry reduction. The structural, vibrational, and optical anisotropies of such core-shell nanostructures are systematically investigated. It is found that the anisotropic absorbance of a core-shell nanowire is obviously higher than that of two single compounds from both theoretical and experimental investigations. Anisotropic photocurrents of the polarization-sensitive photodetectors based on these core-shell SbI3 /Sb2 O3 van der Waals nanowires are measured ranging from ultraviolet (UV) to visible light (360-532 nm). Compared with other van der Waals 1D materials, low anisotropy ratio (Imax /Imin ) is measured based on SbI3 but a device based on this core-shell nanowire possesses a relatively high anisotropy ratio of ≈3.14 under 450 nm polarized light. This work shows that the low-symmetrical core-shell van der Waals heterostructure has large potential to be applied in wide range polarization-sensitive photodetectors.

Template-assisted molten-salt synthesis of hierarchical lithium-rich layered oxide nanowires as high-rate and long-cycling cathode materials

Lithium-rich layered oxides are promising cathode materials for next-generation lithium-ion batteries (LIBs) used in electric vehicles, due to their high specific capacity over 250 mAh g−1 and high energy density of ∼900 Wh Kg−1. However, the poor rate performance and inferior cycling stability of current lithium-rich layered oxides have greatly hindered their practical applications in vehicular LIBs, mostly due to the ineffectiveness of conventional synthesis methods in controlling the materials size and morphology. Herein, one-dimensional (1D) hierarchical lithium-rich layered oxide (Li1.15Mn0.54Co0.08Ni0.23O2) nanowires were successfully synthesized by a template-assisted molten-salt method that used α-MnO2 nanotubes as both the manganese source and template. The prepared lithium-rich layer oxide nanowires were ∼60–80 nm in diameter and ∼0.5–1 μm in length, and each nanowire was composed of homogeneous and interconnected primary nanoparticles (5–20 nm). Electrochemical characterization showed that the 1D lithium-rich layered oxide nanowires exhibited impressively high-rate performance, long cycle life, and excellent capacity retention as cathode materials for LIBs. For example, the cathode delivered a high initial discharge capacity of 304.5 mAh g−1 with a Columbic efficiency of 81.2%, and maintained a discharge capacity of 253.3 mAh g−1, 241 mAh g−1, 222 mAh g−1, and 203 mAh g−1 after 100 cycles, at 0.5C, 1C, 2C and 5C, respectively. Moreover, at an even high rate of 10C, 20C and 30C, the lithium-rich layered oxide nanowires could still deliver a discharge capacity of 149 mAh g−1, 121 mAh g−1, and 65 mAh g−1 respectively for 1000 cycles, without any capacity decay. Post-cycling structural analysis showed that the 1D nanowire morphology of lithium-rich layered oxide was well preserved after prolonged charge/discharge cycling at 10C for 1000 cycles. The excellent electrochemical performance can be ascribed to the good structural stability of 1D nanowires, primary nanosized particles, high crystallinity of the 1D Li1.15Mn0.54Co0.08Ni0.23O2 nanowires. This work developed a new strategy to synthesize manganese-based cathodes with controlled morphology and high crystallinity by the combination of suitable manganese source and molten salt.

Nitrogen-Doped Graphene-Buffered Mn2 O3 Nanocomposite Anodes for Fast Charging and High Discharge Capacity Lithium-Ion Batteries.

Mn2 O3 is a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity and low discharge potential. However, low electronic conductivity and capacity fading limits its practical application. In this work, Mn2 O3 with 1D nanowire geometry is synthesized in neutral aqueous solutions by a facile and effective hydrothermal strategy for the first time, and then Mn2 O3 nanoparticle and nitrogen-doped reduced graphene oxide (N-rGO) are composited with Mn2 O3 nanowires (Mn2 O3 -GNCs) to enhance its volume utilization and conductivity. When used as an anode material for LIBs, the Mn2 O3 -GNCs exhibit high reversible capacity (1350 mAh g-1 ), stable cycling stability, and good rate capability. Surprisingly, the Mn2 O3 -GNC electrodes can also show fast charging capability; even after 200 cycles (charge: 10 A g-1 ; discharge: 0.5 A g-1 ), its discharge capacity can also keep at ≈500 mAh g-1 . In addition, the Mn2 O3 -GNCs also have considerable full cell and supercapacitor performance. The excellent electrochemical performances can be ascribed to the N-rGO network structure and 1D nanowire structure, which can ensure fast ion and electron transportation.

Nanowire-Seeded Growth of Single-Crystalline (010) β-Ga2 O3 Nanosheets with High Field-Effect Electron Mobility and On/Off Current Ratio.

2D β-Ga2 O3 nanosheets, as fundamental materials, have great potential in next generations of ultraviolet transparent electrodes, high-temperature gas sensors, solar-blind photodetectors, and power devices, while their synthesis and growth with high crystalline quality and well-controlled orientation have not been reported yet. The present study demonstrates how to grow single-crystalline ultrathin quasi-hexagonal β-Ga2 O3 nanosheets with nanowire seeds and proposes a hierarchy-oriented growth mechanism. The hierarchy-oriented growth is initiated by epitaxial growth of a single-crystalline β-Ga2 O3 nanowire on a GaN nanocrystal and followed by homoepitaxial growth of quasi-hexagonal (010) β-Ga2 O3 nanosheets. The undoped 2D (010) β-Ga2 O3 nanosheet field effect transistor has a field-effect electron mobility of 38 cm2 V-1 s-1 and an on/off current ratio of 107 with an average subthreshold swing of 150 mV dec-1 . The from-nanowires-to-nanosheets technique paves a novel way to fabricate nanosheets, which has great impact on the field of nanomaterial synthesis and growth and the area of nanoelectronics as well.

Advanced Li‐Ion Batteries with High Rate, Stability, and Mass Loading Based on Graphene Ribbon Hybrid Networks

To optimize the cycle life and rate performance of lithium-ion batteries (LIBs), ultra-fine Fe2 O3 nanowires with a diameter of approximately 2 nm uniformly anchored on a cross-linked graphene ribbon network are fabricated. The unique three-dimensional structure can effectively improve the electrical conductivity and facilitate ion diffusion, especially cross-plane diffusion. Moreover, Fe2 O3 nanowires on graphene ribbons (Fe2 O3 /GR) are easily accessible for lithium ions compared with the traditional graphene sheets (Fe2 O3 /GS). In addition, the well-developed elastic network can not only undergo the drastic volume expansion during repetitive cycling, but also protect the bulk electrode from further pulverization. As a result, the Fe2 O3 /GR hybrid exhibits high rate and long cycle life Li storage performance (632 mAh g-1 at 5 A g-1 , and 471 mAh g-1 capacity maintained even after 3000 cycles). Especially at high mass loading (≈4 mg cm-2 ), the Fe2 O3 /GR can still deliver higher reversible capacity (223 mAh g-1 even at 2 A g-1 ) compared with the Fe2 O3 /GS (37 mAh g-1 ) for LIBs.

Lithium-rich layered oxide nanowires bearing porous structures and spinel domains as cathode materials for lithium-ion batteries

Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li1.2Mn0.54Ni0.13Co0.13O2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li1.2Mn0.54Ni0.13Co0.13O2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li1.2Mn0.54Ni0.13Co0.13O2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration.

Hierarchical Nickel-Cobalt-Based Transition Metal Oxide Catalysts for the Electrochemical Conversion of Biomass into Valuable Chemicals.

The upgrading of biomass into sustainable and valuable fine chemicals is an alternative to the use of state-of-the-art petrochemicals. The conversion of 5-hydroxymethylfurfural (HMF) biomass derivative into 2,5-furandicarboxylic acid (FDCA) has been recognized as an economical and green approach to replace the current polyethylene terephthalate based plastic industry. However, this reaction mostly relies on noble-metal-based catalysts for the sluggish aerobic oxidation of alcohol groups. In this work, we report a series of hierarchical Ni-Co-based transition metal oxide catalysts for HMF oxidation by electrocatalysis. Comprehensive material characterization and electrochemical evaluation have been performed. A 90 % FDCA yield, nearly 100 % Faradaic efficiency, and robust stability were achieved for NiCo2 O4 nanowires. As non-precious-metal catalysts, Ni-Co-based transition metal oxides may open up new potential materials for highly efficient electrochemical biomass upgrading.