Anatase TiO₂: Better Anode Material Than Amorphous and Rutile Phases of TiO₂ for Na-Ion Batteries

Amorphous TiO₂@C nanospheres were synthesized via a template approach. After being sintered under different conditions, two types of polyphase TiO₂ hollow nanospheres were obtained. The electrochemical properties of the amorphous TiO₂ nanospheres and the TiO₂ hollow nanospheres with different phases were characterized as anodes for the Na-ion batteries. It was found that all the samples demonstrated excellent cyclability, which was sustainable for hundreds of cycles with little capacity fading, although the anatase TiO₂ presented a capability that was better than that of the mixed anatase/rutile TiO₂ or the amorphous TiO₂@C. Through crystallographic analysis, it was revealed that the anatase TiO₂ crystal structure supplies two-dimensional diffusion paths for Na-ion intercalation and more accommodation sites. Density functional theory calculations indicated lower energy barriers for the insertion of Na⁺ into anatase TiO₂. Therefore, anatase TiO₂ hollow nanospheres show excellent high-rate performance. Through <i>ex situ</i> field emission scanning electron microscopy, it was revealed that the TiO₂ hollow nanosphere architecture can be maintained for hundreds of cycles, which is the main reason for its superior cyclability

Facile Synthesis of Highly Efficient One-Dimensional Plasmonic Photocatalysts through Ag@Cu₂O Core–Shell Heteronanowires

A novel class of one-dimensional (1D) plasmonic Ag@Cu₂O core–shell heteronanowires have been synthesized at room temperature for photocatalysis application. The morphology, size, crystal structure and composition of the products were investigated by XRD, SEM, TEM, XPS, and UV–vis instruments. It was found the reaction time and the amount of Ag nanowires play crucial roles in the formation of well-defined 1D Ag@Cu₂O core–shell heteronanowires. The resultant 1D Ag@Cu₂O NWs exhibit much higher photocatalytic activity toward degradation of organic contaminants than Ag@Cu₂O core–shell nanoparticles or pure Cu₂O nanospheres under solar light irradiation. The drastic enhancement in photocatalytic activity could be attributed to the surface plasmon resonance and the electron sink effect of the Ag NW cores, and the unique 1D core–shell nanostructure

Fabrication of Hierarchical Porous Carbon Nanoflakes for High-Performance Supercapacitors

In the current work, the carbon nanoflakes (CNs-Fe/KOH) and porous carbon (PC-Ni/KOH) have been produced by using Fe­(NO₃)₃/KOH and Ni­(NO₃)₂/KOH as the cographitization/activation catalysts to treat the natural plane tree fluff, respectively. The as-prepared carbon materials show different morphologies when treated with different metal ions. Compared with PC-Ni/KOH, the CNs-Fe/KOH have both high graphitization degree (<i>I</i>_G/<i>I</i>_D = 1.53) and large <i>S</i>_BET (1416 m²/g). In a three-electrode setup, the CNs-Fe/KOH electrode shows a high specific capacitance of 253 F/g at 10 A/g, with a capacitance retention of 92.64% after 10000 cycles in 2 M H₂SO₄ aqueous solution, which is far better than the sample without Fe³⁺ addition. In 1 M LiPF₆ in ethylene carbonate/diethyl carbonate organic solution, CNs-Fe/KOH-based symmetric supercapacitor also presents an excellent specific capacitance of 32.2 F/g at 1 A/g. In addition, an energy density of 39.98 W h/kg can be achieved at the power density of 1.49 kW/kg. Influence of metal ions on the morphology and structure as well as electrochemical performance of the carbon materials are further analyzed in detail. The current work provides a novel path for design and fabrication of supercapacitor electrode materials with promising electrochemical performances

Enhanced Reaction Kinetics and Structure Integrity of Ni/SnO₂ Nanocluster toward High-Performance Lithium Storage

SnO₂ is regarded as one of the most promising anodes via conversion-alloying mechanism for advanced lithium ion batteries. However, the sluggish conversion reaction severely degrades the reversible capacity, Coulombic efficiency and rate capability. In this paper, through constructing porous Ni/SnO₂ composite electrode composed of homogeneously distributed SnO₂ and Ni nanoparticles, the reaction kinetics of SnO₂ is greatly enhanced, leading to full conversion reaction, superior cycling stability and improved rate capability. The uniformly distributed Ni nanoparticles provide a fast charge transport pathway for electrochemical reactions, and restrict the direct contact and aggregation of SnO₂ nanoparticles during cycling. In the meantime, the void space among the nanoclusters increases the contact area between the electrolyte and active materials, and accommodates the huge volume change during cycling as well. The Ni/SnO₂ composite electrode possesses a high reversible capacity of 820.5 mAh g^–1 at 1 A g^–1 up to 100 cycles. More impressively, large capacity of 841.9, 806.6, and 770.7 mAh g^–1 can still be maintained at high current densities of 2, 5, and 10 A g^–1 respectively. The results demonstrate that Ni/SnO₂ is a high-performance anode for advanced lithium-ion batteries with high specific capacity, excellent rate capability, and cycling stability

Defect Sites-Rich Porous Carbon with Pseudocapacitive Behaviors as an Ultrafast and Long-Term Cycling Anode for Sodium-Ion Batteries

Room-temperature sodium-ion batteries have been regarded as promising candidates for grid-scale energy storage due to their low cost and the wide distribution of sodium sources. The main scientific challenge for their practical application is to develop suitable anodes with long-term cycling stability and high rate capacity. Here, novel hierarchical three-dimensional porous carbon materials are synthesized through an in situ template carbonization process. Electrochemical examination demonstrates that carbonization temperature is a key factor that affects Na⁺-ion-storage performance, owing to the consequent differences in surface area, pore volume, and degree of crystallinity. The sample obtained at 600 °C delivers the best sodium-storage performance, including long-term cycling stability (15 000 cycles) and high rate capacity (126 mAh g^–1 at 20 A g^–1). Pseudocapacitive behavior in the Na⁺-ion-storage process has been confirmed and studied via cyclic voltammetry. Full cells based on the porous carbon anode and Na₃V₂(PO₄)₃-C cathode also deliver good cycling stability (400 cycles). Porous carbon, combining the merits of high energy density and extraordinary pseudocapacitive behavior after cycling stability, can be a promising replacement for battery/supercapacitors hybrid and suggest a design strategy for new energy-storage materials

Synergistically Enhanced Interfacial Interaction to Polysulfide via N,O Dual-Doped Highly Porous Carbon Microrods for Advanced Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have received tremendous attention because of their extremely high theoretical capacity (1672 mA h g^–1) and energy density (2600 W h kg^–1). Nevertheless, the commercialization of Li–S batteries has been blocked by the shuttle effect of lithium polysulfide intermediates, the insulating nature of sulfur, and the volume expansion during cycling. Here, hierarchical porous N,O dual-doped carbon microrods (NOCMs) were developed as sulfur host materials with a large pore volume (1.5 cm³ g^–1) and a high surface area (1147 m² g^–1). The highly porous structure of the NOCMs can act as a physical barrier to lithium polysulfides, while N and O functional groups enhance the interfacial interaction to trap lithium polysulfides, permitting a high loading amount of sulfur (79–90 wt % in the composite). Benefiting from the physical and chemical anchoring effect to prevent shuttling of polysulfides, S@NOCMs composites successfully solve the problems of low sulfur utilization and fast capacity fade and exhibit a stable reversible capacity of 1071 mA h g^–1 after 160 cycles with nearly 100% Coulombic efficiency at 0.2 C. The N,O dual doping treatment to porous carbon microrods paves a way toward rational design of high-performance Li–S cathodes with high energy density

Bismuth Oxybromide with Reasonable Photocatalytic Reduction Activity under Visible Light

The original bismuth-based oxyhalide, known as the Sillén family, is an important photocatalyst due to its high photocatalytic oxidation activity. Here, we report a bismuth-based photocatalyst, Bi₂₄O₃₁Br₁₀, with reasonable reduction activity. The photoreduction capability of Bi₂₄O₃₁Br₁₀ in H₂ evolution from water reduction is 133.9 μmol after 40 h under visible light irradiation. Bi₂₄O₃₁Br₁₀ presents the highest activity among Bi₂O₃, BiOBr, and Bi₂₄O₃₁Br₁₀ in photocatalytic reduction of the Cr (VI) test, and Cr (VI) ions are totally removed in 40 min. The Mott–Schottky test shows the bottom of the conduction band fits the electric potential requirements for splitting water to H₂. First-principles calculations indicate the conduction band of Bi₂₄O₃₁Br₁₀ mainly consists of hybridized Bi 6p and Br 4s orbitals, which may contribute to the uplifting of the conduction band

Reverse Microemulsion Synthesis of Sulfur/Graphene Composite for Lithium/Sulfur Batteries

Due to its high theoretical capacity, high energy density, and easy availability, the lithium–sulfur (Li–S) system is considered to be the most promising candidate for electric and hybrid electric vehicle applications. Sulfur/carbon cathode in Li–S batteries still suffers, however, from low Coulombic efficiency and poor cycle life when sulfur loading and the ratio of sulfur to carbon are high. Here, we address these challenges by fabricating a sulfur/carboxylated–graphene composite using a reverse (water-in-oil) microemulsion technique. The fabricated sulfur–graphene composite cathode, which contains only 6 wt % graphene, can dramatically improve the cycling stability as well as provide high capacity. The electrochemical performance of the sulfur–graphene composite is further enhanced after loading into a three-dimensional heteroatom-doped (boron and nitrogen) carbon-cloth current collector. Even at high sulfur loading (∼8 mg/cm²) on carbon cloth, this composite showed 1256 mAh/g discharge capacity with more than 99% capacity retention after 200 cycles