Shuqiang Jiao

A new cathode material for super-valent battery based on aluminium ion intercalation and deintercalation

Due to their small footprint and flexible siting, rechargeable batteries are attractive for energy storage systems. A super-valent battery based on aluminium ion intercalation and deintercalation is proposed in this work with VO2 as cathode and high-purity Al foil as anode. First-principles calculations are also employed to theoretically investigate the crystal structure change and the insertion-extraction mechanism of Al ions in the super-valent battery. Long cycle life, low cost and good capacity are achieved in this battery system. At the current density of 50 mAg−1, the discharge capacity remains 116 mAhg−1 after 100 cycles. Comparing to monovalent Li-ion battery, the super-valent battery has the potential to deliver more charges and gain higher specific capacity.

Efficient visible-light-driven photocatalytic hydrogen production using CdS@TaON core–shell composites coupled with graphene oxide nanosheets

Large-scale hydrogen production through water splitting using photocatalysts with solar energy can potentially produce clean fuel from renewable resources. In this work, photocatalytic evolution of H2 with a high efficiency was achieved using graphene oxide (GO) nanosheets decorated with CdS sensitized TaON core–shell composites (GO–CdS@TaON). The CdS@TaON core–shell nanocomposites were prepared by an ion-exchange route with assistance from a hydrothermal process on GO as the support. The TaON core–shell composites containing 1 wt% CdS nanocrystals showed a high rate of H2-production at 306 μmol h−1 with an apparent quantum efficiency (QE) of 15% under 420 nm monochromatic light. The rate of hydrogen formation was 68 times faster in comparison with the rate observed on pure TaON. The rate was further increased to 633 μmol h−1 with a high quantum efficiency of 31% when the GO–CdS@TaON hybrid composite was coupled with 1 wt% of graphene oxide and 0.4 wt% of Pt (about 141 times higher than that of the pristine TaON). This high photocatalytic H2-production activity is ascribed firstly to the presence of CdS nanocrystals that alter the energy levels of the conduction and valence bands in the coupled semiconductor system; secondly to the involvement of graphene oxide that serves as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from CdS@TaON composites. This investigation can open up new possibilities for the development of highly efficient TaON-based photocatalysts that utilize visible light as an energy source.

Microspheric Na2Ti3O7 consisting of tiny nanotubes: an anode material for sodium-ion batteries with ultrafast charge–discharge rates

Conventionally, rechargeable batteries with a fast charge-discharge rate, while being able to be implemented in large-scale applications with low prices, are critical for new energy storage systems. In this work, first-principles simulations were employed to theoretically investigate the insertion of sodium into the Na(2)Ti(3)O(7) structure. The result discovered that the theoretical capacity of Na(2)Ti(3)O(7) was 311 mA h g(-1). Furthermore, a microspheric Na(2)Ti(3)O(7) material consisting of tiny nanotubes of ca. 8 nm in outside diameter and a few hundred nanometers in length has been synthesized. The galvanostatic charge-discharge measurements, using the as-prepared Na(2)Ti(3)O(7) nanotubes as a working electrode with a voltage range of 0.01-2.5 V vs. Na(+)/Na, disclosed that a high capacity was maintained even under an ultrafast charge-discharge rate. At a current density of 354 mA g(-1), the discharge capacity was maintained at 108 mA h g(-1) over 100 cycles. Even at a very large current density of 3540 mA g(-1), the discharge capacity was still 85 mA h g(-1). HRTEM analysis and electrochemical tests proved that sodium ions could not only intercalate into the Na(2)Ti(3)O(7) crystal, but could also be stored in the intracavity of the nanotubes. All of the results disclose that the as-prepared Na(2)Ti(3)O(7) nanotubes are able to be used as anode materials in large-scale applications for rechargeable sodium-ion batteries at low cost while maintaining excellent performance.

Single crystalline Na2Ti3O7 rods as an anode material for sodium-ion batteries

Single crystalline Na2Ti3O7 rods were prepared through sintering a precursor synthesized in a reverse micelle. Charge/discharge measurements were performed in the potential range 0.01–2.5 V versus Na/Na+ under different C-rates. The tested capacity was maintained at 103 mA h g−1, even after 20 cycles at a rate of 0.1 C. The results exhibited that the as-prepared single crystalline Na2Ti3O7 rods had a very low voltage plateau (around 0.3 V), and were suitable to use as anode materials for sodium-ion batteries.

3D Bi12TiO20/TiO2 hierarchical heterostructure: Synthesis and enhanced visible-light photocatalytic activities

A three-dimensional (3D) multicomponent oxide, Bi(12)TiO(20)/TiO(2) hierarchical heterostructure was successfully synthesized via a one-step and template-free hydrothermal route. X-ray diffraction and X-ray photoelectron spectroscopy measurements confirm that the composition of the as-fabricated sample is Bi(12)TiO(20)/TiO(2) composite. Scanning and transmission electron microscopy observation reveals that the as-synthesized sample is microsized flower-like hierarchical networks consisted of Bi(12)TiO(20) nanorods decorated with the primary TiO(2) nanoparticles. Extension of the light absorption from the ultraviolet region to the visible-light region was confirmed by UV-vis absorption spectra. Due to the structure-property relationships, the 3D Bi(12)TiO(20)/TiO(2) heterostructure exhibited enhanced visible photocatalytic activity over that of Bi(12)TiO(20) and TiO(2) samples in the decomposition of Rhodamine B in water which is a typical model pollutant. The enhanced photocatalytic activity can be attributed to the extended absorption in the visible light region resulting from the 3D Bi(12)TiO(20)/TiO(2) heterostructures, and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Bi(12)TiO(20)/TiO(2) junction interface, demonstrating that the Bi(12)TiO(20)/TiO(2) heterostructure is a promising candidate as a visible light photocatalyst.

Cobalt-bilayer catalyst decorated Ta3N5 nanorod arrays as integrated electrodes for photoelectrochemical water oxidation

Ta3N5 nanorod arrays were fabricated by nitridation of fluorine-containing tantalum oxide (F–Ta2O5) nanorod arrays grown in situ on Ta substrates by a one-pot vapour-phase hydrothermal induced self-assembly technique. In this protocol, the in situ generation and the morphology of arrays elaborately adjusted by reaction time, play a vital role in the formation of the F–Ta2O5 nanorod arrays and a highly conductive interlayer between the nanorods and the substrate. Due to the shape anisotropy, ordered hierarchical structure and high surface area, a high photoelectrochemical activity was achieved by the optimum Ta3N5 nanorod photoelectrode with a photocurrent density of 1.22 mA cm−2 under AM 1.5G irradiation at 1.23 V vs. RHE (reversible hydrogen electrode). Furthermore, a higher and more stable photocurrent was demonstrated by combining the highly active Ta3N5 nanorods with stable Co3O4/Co(OH)2 (Co3O4/Co(II)) bilayer catalysts when compared with that demonstrated for Co(II)/Ta3N5 and Co3O4/Ta3N5 photoelectrodes, exhibiting that not only is the onset potential negatively shifted but also the photocurrent and the stability are significantly improved, which is correlated to an order of magnitude reduction in the resistance to charge transfer at the Ta3N5/H2O interface. Specifically, about 92% of the initial stable photocurrent remains after long-term irradiation at 1.23 V vs. RHE. At 1.23 V vs. RHE, the photocurrent density of Co3O4/Co(II)/Ta3N5 arrays reached 3.64 mA cm−2 under AM 1.5G simulated sunlight at 100 mW cm−2, and a maximum IPCE of 39.5% was achieved at 440 nm. This combination of catalytic activity, stability, and conformal decoration makes this a promising approach to improve the photoelectrochemical performance of photoanodes in the general field of energy conversion.

Hierarchical metastable γ-TaON hollow structures for efficient visible-light water splitting

Hierarchical tantalum-based oxide and (oxy)nitride with hollow urchin-like nanostructures have been synthesized for the first time by an in situ self-assembly wet-chemical route in addition with post-thermal nitridation. Notably, a single-phase metastable γ-TaON with hollow urchin-like spheres among the tantalum (oxy)nitrides was obtained during the phase transformation process from an orthorhombic Ta2O5 to a typical monoclinic β-TaON, corresponding the order of phase formation: Ta2O5 → γ-TaON → β-TaON → Ta3N5. The combined effect of the crystal and electronic structures and hierarchical morphology on the tunable photocatalytic and photoelectrochemical performances of the tantalum-based photocatalysts was systematically investigated. Efficient photocatalytic hydrogen production as high as 381.6 μmol h−1 with an apparent quantum efficiency of 9.5% under 420 nm irradiation (about 47.5 times higher than that of the conventional TaON) was achieved over this metastable γ-TaON architecture. Furthermore, the hierarchical γ-TaON photoanode exhibited a photocurrent density of ∼1.4 mA cm−2 at 0.8 V vs. SCE in Na2SO4 solution under visible light irradiation. This excellent photocatalytic activity is ascribed to the unique urchin-like nanostructure with large specific surface area, the metastable crystal structure and appropriate electronic structure as well as the efficient charge carrier separation.

Bi2O3 quantum-dot decorated nitrogen-doped Bi3NbO7 nanosheets: in situ synthesis and enhanced visible-light photocatalytic activity

The Bi2O3 quantum dots decorated nitrogen doped Bi3NbO7 nanosheets (Bi2O3/N-Bi3NbO7) were successfully synthesized via a facile in situ hydrothermal process as a straightforward protocol. The peony-like N-Bi3NbO7 hierarchical architectures decorated with surface enrichment of Bi2O3 quantum dots were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, UV-vis diffuse reflectance spectrum and photoluminescence spectra. The as-prepared Bi2O3/N-Bi3NbO7 heterostructures exhibited higher photocatalytic activities in the decomposition of model pollutants under visible-light irradiation than N-Bi3NbO7 nanosheets in the absence of any expensive metal components and co-catalysts, which could be attributed to the enhanced light absorbance multiple reflections in the heterostructures, the enhanced photosensitizing effect of the surface enriched Bi2O3 quantum dots and the strong interaction between Bi2O3 and N-Bi3NbO7. Furthermore, the Bi2O3/N-Bi3NbO7 heterostructures exhibited strong durability that may be ascribed to the high hydrothermal stability of the flower-like structure and the inhibition of Bi2O3 leaching owing to its tight chemical bonding with N-Bi3NbO7 nanosheets.

High-Performance Aluminum-Ion Battery with CuS@C Microsphere Composite Cathode

On the basis of low-cost, rich resources, and safety performance, aluminum-ion batteries have been regarded as a promising candidate for next-generation energy storage batteries in large-scale energy applications. A rechargeable aluminum-ion battery has been fabricated based on a 3D hierarchical copper sulfide (CuS) microsphere composed of nanoflakes as cathode material and room-temperature ionic liquid containing AlCl3 and 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) as electrolyte. The aluminum-ion battery with a microsphere electrode exhibits a high average discharge voltage of ∼1.0 V vs Al/AlCl4-, reversible specific capacity of about 90 mA h g-1 at 20 mA g-1, and good cyclability of nearly 100% Coulombic efficiency after 100 cycles. Such remarkable electrochemical performance is attributed to the well-defined nanostructure of the cathode material facilitating the electron and ion transfer, especially for chloroaluminate ions with large size, which is desirable for aluminum-ion battery applications.

Hierarchical nitrogen doped bismuth niobate architectures: Controllable synthesis and excellent photocatalytic activity

Nitrogen doped bismuth niobate (N-Bi(3)NbO(7)) hierarchical architectures were synthesized via a facile two-step hydrothermal process. XRD patterns revealed that the defect fluorite-type crystal structure of Bi(3)NbO(7) remained intact upon nitrogen doping. Electron microscopy showed the N-Bi(3)NbO(7) architecture has a unique peony-like spherical superstructure composed of numerous nanosheets. UV-vis spectra indicated that nitrogen doping in the compound results in a red-shift of the absorption edge from 450nm to 470nm. XPS indicated that [Bi/Nb]N bonds were formed by inducing nitrogen to replace a small amount of oxygen in Bi(3)NbO(7-x)N(x), which is explained by electronic structure calculations including energy band and density of states. Based on observations of architectures formation, a possible growth mechanism was proposed to explain the transformation of polyhedral-like nanoparticles to peony-like microflowers via an Ostwald riping mechanism followed by self-assembly. The N-Bi(3)NbO(7) architectures due to the large specific surface area and nitrogen doping exhibited higher photocatalytic activities in the decomposition of organic pollutant under visible-light irradiation than Bi(3)NbO(7) nanoparticles. Furthermore, an enhanced photocatalytic performance was also observed for Ag/N-Bi(3)NbO(7) architectures, which can be attributed to the synergetic effects between noble metal and semiconductor component.