A new, slack, and uniformly porous TiO2 material is synthesized by a simple, carbon nanotube (CNT) template‐assisted hydrothermal method and is further explored for protein immobilization and biosensing. Results demonstrate that the material has a large specific surface area and a unique nanostructure with a uniform pore‐size distribution. Glucose oxidase (GOD) immobilized on the material exhibits facile, direct electrochemistry and good electrocatalytic performance without any electron mediator. The fabricated glucose oxidase sensor shows good stability and high sensitivity, which indicates that the slack porous TiO2 is an attractive material for use in the fabrication of biosensors, particularly enzymatic sensors, because of its direct electrochemistry, high specific surface area, and unique nanostructure for efficient immobilization of biomolecules.

A unique nanostructured polyaniline (PANI)/mesoporous TiO(2) composite was synthesized and explored as an anode in Escherichia coli microbial fuel cells (MFCs). The results of X-ray diffraction, morphology, and nitrogen adsorption-desorption studies demonstrate a networked nanostructure with uniform nanopore distribution and high specific surface area of the composite. The composite MFC anode was fabricated and its catalytic behavior investigated. Optimization of the anode shows that the composite with 30 wt % PANI gives the best bio- and electrocatalytic performance. A possible mechanism to explain the excellent performance is proposed. In comparison to previously reported work with E. coli MFCs, the composite anode delivers 2-fold higher power density (1495 mW/m(2)). Thus, it has great potential to be used as the anode for a high-power MFC and may also provide a new universal approach for improving different types of MFCs.

No abstract

Transition-metal phosphides (TMPs) have emerged as promising catalyst candidates for the hydrogen evolution reaction (HER). Although numerous methods have been investigated to obtain TMPs, most rely on traditional synthetic methods that produce materials that are inherently deficient with respect to electrical conductivity. An electrospinning-based reduction approach is presented, which generates nickel phosphide nanoparticles in N-doped porous carbon nanofibers (Ni P@NPCNFs) in situ. Ni P nanoparticles are protected from irreversible fusion and aggregation in subsequent high-temperature pyrolysis. The resistivity of Ni P@NPCNFs (5.34 Ω cm) is greatly decreased by 10 times compared to Ni P (>10 Ω cm) because N-doped carbon NFs are incorporated. As an electrocatalyst for HER, Ni P@NPCNFs reveal remarkable performance compared to other previously reported catalysts in acidic media. Additionally, it offers excellent catalytic ability and durability in both neutral and basic media. Encouraged by the excellent electrocatalytic performance of Ni P@NPCNFs, a series of pea-like M P@NPCNFs, including Fe P@NPCNFs, Co P@NPCNFs, and Cu P@NPCNFs, were synthesized by the same method. Detailed characterization suggests that the newly developed method could render combinations of ultrafine metal phosphides with porous carbon accessible; thereby, extending opportunities in electrocatalytic applications.

The practical application of lithium-sulfur (Li-S) batteries remains remote because of rapid capacity fade caused by the low conductivity of sulfur, dissolution of intermediate lithium polysulfides, severe volumetric expansion, and slow redox kinetics of polysulfide intermediates. Here, to address these obstacles, a new sulfiphilic and highly conductive honeycomb-like spherical cathode host constructed from hollow metallic and polar Co 9 S 8 tubes is designed. Co 9 S 8 can effectively bind polar polysulfides for prolonged cycle life, due to the strong chemisorptive capability for immobilizing the polysulfide species. The hollow structure, as the sulfur host, can further prevent polysulfide dissolution and offer sufficient space to accommodate the necessary volume expansion. Well-aligned tubular arrays provide a conduit for rapid conduction of electrons and Li-ions. More importantly, the experimental results and theoretical calculations show that Co 9 S 8 plays an important catalytic role in improving the electrochemical reaction kinetics. When used as cathode materials for Li-S batteries, the S@Co 9 S 8 composite cathode exhibits high capacity and an exceptional stable cycling life demonstrated by tests of 600 cycles at 1 C with a very low capacity decay rate of only ≈0.026% per cycle.

A new well-aligned cone-shaped nanostructure of polypyrrole (WACNP) has been successfully grown on Au substrate by using a simple, one-step, reliable, and template-free anodic deposition method. The formation mechanism of WACNP is proposed, in which the hydrogen bonding introduced from phosphate buffer solution (PBS) promotes the formation of a well-aligned nanostructure of polypyrrole (PPy), while the steric hindrance effect arisen from high concentration of pyrrole (Py) boosts its vertical alignment and further forms a cone-shaped nanostructure. The 3D, arrayed, nanotubular architecture coated with an ultrathin layer of RuO2 by the magnetron sputtering deposition method was tailored to construct a supercapacitor. The unique structure and design not only reduces the diffusion resistance of electrolytes in the electrode material but also enhances its electrochemical performance. The modification of RuO2 on WACNP results in a capacitance higher than that of WACNP by three times. The specific capacitance of RuO2/WACNP is 15.1 mF cm−2 (∼302 F g−1) measured by the charge−discharge method with an applied current density of 0.5 mA cm−2 over a potential range of −0.2 to 0.7 V, and is greater than that of commercial carbon materials by 2−3 orders of magnitude. The high capacitance and good stability of the RuO2/WACNP electrode is very promising for applications in microsupercapacitor devices.

No abstract

To tackle aforementioned challenges, intensive efforts have been carried out to design optimized carbon/sulfur cathodes, such as compositing sulfur with mesoporous carbon, [5] carbon nanofibers, [6] carbon nanotubes, [7] carbon spheres, [8] and graphene. [9] Although these carbon-based materials greatly improve the electric conductivity of electrode thereby providing high capacities, [10] the weak interaction between nonpolar carbon and polar polysulfides is not sufficient to limit the dissolution of LiPSs. To further boost the polysulfides adsorption capability and promote the redox reaction kinetics, various polar sulfur host, including metal, metal oxides, metal sulfides, and perovskite [11][12][13][14] are engineered as ideal candidates to not only possess good bonds between polar material and LiPSs, but also accelerate the conversion of LiPSs to solid Li 2 S 2 /Li 2 S, giving rise to a good cycling stability.Heterostructures constructed from coupling nanocrystals with different bandgaps have attracted extensive attention and widely used in photocatalysis, sensor, and energy storage. [15] Benefiting from the internal electric field at heterointerfaces, heterostructures can facilitate charge transport and enhance the surface reaction kinetics. [16] Inspired by the unique advantages of heterostructures, we propose and construct a doubleshelled NiO-NiCo 2 O 4 heterostructure@C hollow nanocages as an efficient sulfur host for advanced Li-S batteries. NiO has strong adsorption for LiPSs that can remarkably immobilize LiPSs through physical and chemical interactions at molecular level. [17] However, the low electrical conductivity makes it difficult for the immobilized LiPSs to fully involve in the electrochemical reactions, thus slowing the redox kinetics of LiPSs conversion reactions. Introducing NiCo 2 O 4 that possesses much better electrical conductivity and higher redox activity into nickel oxides can promote electron transfer for LiPSs conversion reactions. [18] The synthetic approach to the S/NiO-NiCo 2 O 4 @C composite is schematically shown in Figure 1a (for experimental details, see the Supporting Information). Uniform Ni-Co prussian blue analogue (PBA) nanocube precursor was first prepared by a facile coprecipitation strategy. Afterward, double-shelled NiO-NiCo 2 O 4 heterostructure@C nanocages were obtained through a facile calcination treatment coupled with a simple hydrothermal carbon-coating process. After a melt-diffusion process, Double-shelled NiO-NiCo 2 O 4 heterostructure@carbon hollow nanocages as efficient sulfur hosts are synthesized to overcome the barriers of lithiumsulfur (Li-S) batteries simultaneously. The double-shelled nanocages can prevent the diffusion of lithium polysulfides (LiPSs) effectively. NiO-NiCo 2 O 4 heterostructure is able to promote polysulfide conversion reactions. Furthermore, the thin carbon layer outside can improve the electrical conductivity during cycling. Besides, such unique double-shelled hollow nanocage architecture can also accommodate the volumetric eff...