Longhai Zhang

Template-engaged synthesis of uniform mesoporous hollow NiCo2O4 sub-microspheres towards high-performance electrochemical capacitors

An efficient template-engaged synthetic strategy, where silica spheres were applied as hard templates, was developed to synthesize hierarchical mesoporous hollow NiCo2O4 sub-microspheres assembled entirely from ultrathin nanosheets with a thickness of a few nanometers. The as-prepared mesoporous hollow NiCo2O4 sub-microspheres are very uniform in size, mesoporous in textual property, and structurally robust benefiting from the in situ template removal. The morphologies of the hollow sub-microspherical architecture can be tuned easily by varying the concentrations of Ni2+, Co2+, and the precipitant. When evaluated as an appealing electroactive material for electrochemical capacitors (ECs), the as-fabricated hierarchical hollow NiCo2O4 sub-microspheres delivered a specific capacitance (SC) of 678 F g−1 at a current density of 1 A g−1, and even kept it as high as 540 F g−1 at 10 A g−1. Additionally, a desirable cycling stability of 13% SC degradation over 3500 continuous cycles at a current density of 10 A g−1 is observed, suggesting their promising application in advanced ECs.

Hierarchical Porous ZnMn2O4 Hollow Nanotubes with Enhanced Lithium Storage toward Lithium-Ion Batteries

We have purposefully developed a smart template-engaged methodology to efficiently fabricate well-defined ternary spinel ZnMn2 O4 hollow nanotubes (NTs). The procedure involves coating carbon nanotubes (CNTs) with ZnMn2 O4 nanosheets (NSs), followed by heating at high temperature in air to oxidize the CNT template. Physicochemical characterization demonstrated that the formed ZnMn2 O4 NTs with a diameter of approximately 100 nm were composed of assembled NSs and/or nanoparticles (NPs) as building blocks and possessed numerous nanopores of several nanometers in the sidewall of the NTs. In favor of the intrinsic structural advantages, the resulting ZnMn2 O4 NTs exhibited superior electrochemical lithium-storage performance with a large capacity, good rate behavior, and excellent cyclability when evaluated as promising anodes for lithium-ion batteries (LIBs). The remarkable electrochemical performance was rationally ascribed to the appealing one-dimensional (1D) porous hollow tubular architecture with nanoscale subunits and mesopores in the sidewalls, which decreased the diffusion length for the Li(+) ions, improved the kinetic process, and enhanced the structural integrity with sufficient void space to tolerate the volume variation during Li(+) -ion insertion/extraction. These results highlight the promising application of 1D ZnMn2 O4 NTs as anodes for high-performance LIBs.

Scalable Room‐Temperature Synthesis of Mesoporous Nanocrystalline ZnMn2O4 with Enhanced Lithium Storage Properties for Lithium‐Ion Batteries

In this work, we put forward a facile yet efficient room-temperature synthetic methodology for the smart fabrication of mesoporous nanocrystalline ZnMn2O4 in macro-quality from the birnessite-type MnO2 phase. A plausible reduction/ion exchange/re-crystallization mechanism is tentatively proposed herein for the scalable synthesis of the spinel phase ZnMn2O4. When utilized as a high-performance anode for advanced Li-ion battery (LIB) application, the as-synthesized nanocrystalline ZnMn2O4 delivered an excellent discharge capacity of approximately 1288 mAh g(-1) on the first cycle at a current density of 400 mA g(-1), and exhibited an outstanding cycling durability, rate capability, and coulombic efficiency, benefiting from its mesoporous and nanoscale structure, which strongly highlighted its great potential in next-generation LIBs. Furthermore, the strategy developed here is very simple and of great importance for large-scale industrial production.

One-step hydrothermal fabrication of strongly coupled Co3O4 nanosheets–reduced graphene oxide for electrochemical capacitors

In the work, we developed a one-step synthetic strategy to prepare a strongly coupled Co3O4 nanosheets–reduced graphene oxide (Co3O4 NSs–rGO) hybrid, and further utilized it as a promising electroactive material for electrochemical capacitors (ECs). During the hydrothermal procedure, the GO was reduced and Co3O4 NSs were in situ grown on the rGO sheets simultaneously due to the electrostatic interaction between the Co2+ and GO sheets. Electrochemical characteristics indicated that the Co3O4 NSs–rGO hybrid with ∼7.2 wt% Co3O4 loading delivered a specific capacitance (SC) of 187 F g−1 at 1.2 A g−1. Furthermore, the SC degradation of the hybrid was ∼6 and 9% at constant current densities of 1.2 and 5 A g−1 after 1000 continuous charge–discharge cycles, demonstrating its desirable electrochemical stability. The synergetic effect of nanoscale size and good redox activity of the Co3O4 NSs combined with the high electronic conductivity of the rGO resulted in the enhanced electrochemical utilization at high rates. In addition, an activated carbon/Co3O4 NSs–rGO asymmetric EC was further fabricated, and exhibited a specific energy density of ∼13.4 W h kg−1, specific power density of ∼2166 W kg−1 and striking electrochemical stability with ∼11% SC degradation after 1000 cycles.

Ultrafast spray pyrolysis fabrication of a nanophase ZnMn2O4 anode towards high-performance Li-ion batteries

In this study, a facile, ultrafast and green spray pyrolysis strategy was developed well to efficiently fabricate nanophase ZnMn2O4 (ZMO–W) with homogeneous composition from an aqueous spray solution of manganous acetate and zinc acetate. Compared with other ZMO samples prepared by utilizing absolute ethanol and ethylene glycol as solvents, the ZMO–W product displayed competitively cost-effective advantages with the comprehensive consideration of cost and performance. When evaluated as a promising anode for Li-ion batteries (LIBs), the resultant ZMO–W exhibited large initial specific capacity (∼1023 mA h g−1), good rate capability, and excellent cycling stability (average capacity degradation of only ∼4.0% per cycle) at 1 C rate. Benefiting from an ultrafast reaction process in seconds, a high yield (∼100%), environmental friendliness (no NOx emission) and simple equipment requirements (just a tubular furnace), the synthetic methodology we developed here possesses significant potential for rapid large-scale production of advanced ZMO and even other binary transition metal oxides for industrial applications of LIBs.

Microwave-assisted interfacial hydrothermal fabrication of hydrophobic CdWO4 microspheres as a high-performance photocatalyst

In this work, we successfully developed a facile yet efficient microwave-assisted interfacial hydrothermal strategy to fabricate CdWO4 microspheres with a hydrophobic surface as an advanced photocatalyst for photocatalytic degradation of the dye Methyl Orange (MO) under ultraviolet (UV) light irradiation. The as-synthesized CdWO4 microspheres exhibited excellent photocatalytic degradation efficiency of 100% under UV illumination for 80 min, benefiting from its appropriate band gap, strong UV absorption, hydrophobic surface, and low recombination rate of photo-generated charge carriers. The striking stability and easy separation of the unique CdWO4 microspheres further promised its practical recycling usage. Also, insights into the formation and degradation mechanisms of CdWO4 microspheres were tentatively proposed.

Facile synthesis of Co2P2O7 nanorods as a promising pseudocapacitive material towards high-performance electrochemical capacitors

In the present work, we developed an efficient one-step template-free strategy to fabricate intriguing one-dimensional (1D) Co2P2O7 nanorods (NRs) at room temperature, and utilized the unique monoclinic Co2P2O7 NRs as an excellent electrode material for high-performance pseudocapacitors using 3 M KOH as an electrolyte. Strikingly, the as-synthesized 1D Co2P2O7 NR electrode delivered a specific capacitance (SC) of 483 F g−1 at 1 A g−1, and even at 402 F g−1 a high current loading of 10 A g−1. And the SC retention of ∼90% over continuous 3000 charge–discharge cycles at a current density of 6 A g−1confirmed its stable long-term cycling ability at high current density. More significantly, the underlying electrochemical energy-storage mechanism of the Co2P2O7 NR electrode in alkaline KOH aqueous solution was tentatively proposed. And the appealing strategy was proposed for future exploration and development of other low-cost pseudocapacitive materials for next-generation ECs.

Green interfacial synthesis of two-dimensional poly(2,5-dimethoxyaniline) nanosheets as a promising electrode for high performance electrochemical capacitors

2D poly(2,5-dimethoxyaniline) nanosheets were first designed and tailored as intriguing pseudo-capacitive electrode for advanced supercapacitors via green interfacial synthetic strategy, and yielded large specific capacitance (SC) and remarkable SC retention at high rates in 1 M HCl electrolyte.

FACILE SYNTHESIS AND UNUSUAL ELECTROCHEMICAL CAPACITANCE OF Ni-DOPED TITANATE NANOTUBES

In this paper, we developed an intriguing ion-exchange reaction to synthesize Ni-doped titanate nanotubes (Ni-Ti-NTs), and utilized the sample as an appealing pseudocapacitive electrode for electrochemical capacitors (ECs). The energy storage mechanism of the resulting Ni-Ti-NTs electrode in alkaline KOH aqueous electrolyte was further tentatively proposed. Compared with the pristine titanate nanotubes (Ti-NTs), Ni-Ti-NTs with rich porous channels possessed much better electronic conductivity and larger specific surface area, rendering the electrons and OH− ions easily contact the Ni species uniformly distributed on their surfaces for efficient energy storage at high rates. Remarkably, the SC of the Ni-Ti-NTs electrode increased with further cycling, and even reached a SC of 278 F g−1 at a current density of 2 A g−1 after 7500 charge–discharge cycles without relaxation. The prominent electrochemical performance demonstrated that the Ni-Ti-NTs would be a promising candidate and/or even excellent support fo...