N-doped carbon nanotubes from functional tubular polypyrrole: A highly efficient electrocatalyst for oxygen reduction reaction

Aerophobic P-MoS2 on MOF-Derived Co,N-Codoped Carbon Nanosheets with Accelerated H2 Bubble Release Dynamics for Efficient Alkaline Water Splitting at 1000 mA cm-2

Rapid bubble release at high current densities results in the detachment of catalysts and performance degradation, posing a persistent challenge in actual alkaline water electrolysis (AWE). Here, hierarchical nanosheet structures (CoNC@P-MoS2) are constructed, with P-doped MoS2 on the surface of Co,N-codoped carbon. It exhibits low hydrogen evolution reaction overpotentials of 30 and 354 mV at 10 and 1000 mA cm-2 in 1 M KOH, respectively, with a small Tafel slope of 36 mV dec-1. The constructed CoNC@P-MoS2||NiFe-DLH cell requires only 1.44 and 1.92 V to achieve overall water splitting at 10 and 1000 mA cm-2, which outperforms the traditional catalysts like Pt/C||IrO2. The introduction of P stabilizes surface hydroxyl (OH*) and increases the proton penetration depth, thereby greatly enhancing its intrinsic activity. It also makes the surface aerophobic by introducing more microfeatures, which greatly improves the geometric activity by increasing the bubble release rate (∼5.8 times). Low energy consumption of 3.92 kW h Nm-3 was achieved with an energy efficiency close to 80%. Bubble growth kinetics analysis reveals that the time and growth factors for CoNC@P-MoS2 are increased to 0.54 and 11.79 from 0.45 and 6.09 for CoNC, respectively, which highlights its fast bubble reaction dynamics. The results suggest the feasibility of CoNC@P-MoS2 as a potential high-performance catalyst in commercial AWE.

Few-Layered WS2 Anchored on Co, N-Doped Carbon Hollow Polyhedron for Oxygen Evolution and Hydrogen Evolution

Tungsten disulfide (WS₂) is well known to have great potential as an electrocatalyst, but the practical application is hampered by its intrinsic inert plane and semiconductor properties. In this work, owing to a Co-based zeolite imidazole framework (ZIF-67) that effectively inhibited WS₂ growth, few-layered WS₂ was confined to the surface of Co, N-doped carbon polyhedron (WS₂@Co₉S₈), with more marginal active sites and higher conductivity, which promoted efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). For the first time, WS₂@Co₉S₈ was prepared by mixing in one pot of a liquid phase and calcination, and WS₂ realized uniform distribution on the polyhedron surface by electrostatic adsorption in the liquid phase. The obtained hybrid catalyst exhibited excellent OER and HER catalytic activity, and the OER potential was only 15 mV at 10 mA cm^-2 higher than that of noble metal oxide (RuO₂). The improvement of catalytic activity can be attributed to the enhanced exposure of sulfur edge sites by WS₂, the unique synergistic effect between WS₂ and Co₉S₈ on the metal-organic framework (MOF) surface, and the effective shortening of the diffusion path by the hollow multi-channel structure. Therefore, the robust catalyst (WS₂@Co₉S₈) prepared by a simple and efficient synthesis method in this work will serve as a highly promising bifunctional catalyst for OER and HER.

Development of oxidized hydroxyethyl cellulose-based hydrogel enabling unique mechanical, transparent and photochromic properties for contact lenses

With the development of smart devices, higher requirements are put forward for the stimuli-responsive materials. Stimuli-hydrogels as one kind of stimuli-responsive materials with hydrophilicity, demonstrate huge potential in developing intelligent devices for biomedical application. On this basis, we herein report that a sample method was devised to develop a novel composite hydrogel mainly based on oxidized hydroxyethyl cellulose and allyl co-polymer. Subsequently, a series of tests toward this oxidized hydroxyethyl cellulose-based hydrogel due to its structure and performance was applied. Here, the oxidized hydroxyethyl cellulose molecular chains were used as biomacromolecule templates to form Schiff base, borate and hydrogen bonds to obtain unique mechanical properties (fast recovery with almost no-hysteresis and remarkable compressive capacity), while a double bond functionalized spirooxazine (allyl spirooxazine derivative) was applied to endow photo- and pH sensitivity to the oxidized hydroxyethyl cellulose-based transparent hydrogel (T% = 93%) substrate. Furthermore, the oxidized hydroxyethyl cellulose-based hydrogel did exhibit good pH environment adaptability and noncytotoxicity in vitro test. Based on the advanced characteristics, the designed oxidized hydroxyethyl cellulose-based hydrogel has potential applications prospect in the development of safe, fashionable and pH- detectable contact lenses, thereby providing a new strategy for the development of smart, stylish contact lenses.

Ultrafast-charging and long cycle-life anode materials of TiO2-bronze/nitrogen-doped graphene nanocomposites for high-performance lithium-ion batteries

Emerging technologies demand a new generation of lithium-ion batteries that are high in power density, fast-charging, safe to use, and have long cycle lives. This work reports charging rates and specific capacities of TiO2(B)/N-doped graphene (TNG) composites. The TNG composites were prepared by the hydrothermal method in various reaction times (3, 6, 9, 12, and 24 h), while the N-doped graphene was synthesized using the modified Hummer's method followed by a heat-treatment process. The different morphologies of TiO2 dispersed on the N-doped graphene sheet were confirmed as anatase-nanoparticles (3, 6 h), TiO2(B)-nanotubes (9 h), and TiO2(B)-nanorods (12, 24 h) by XRD, TEM, and EELS. In electrochemical studies, the best battery performance was obtained with the nanorods TiO2(B)/N-doped graphene (TNG-24h) electrode, with a relatively high specific capacity of 500 mA h g-1 at 1C (539.5 mA g-1). In long-term cycling, excellent stability was observed. The capacity retention of 150 mA h g-1 was observed after 7000 cycles, at an ultrahigh current of 50C (27.0 A g-1). The synthesized composites have the potential for fast-charging and have high stability, showing potential as an anode material in advanced power batteries for next-generation applications.

Highly selective two-electron oxygen reduction to generate hydrogen peroxide using graphite felt modified with N-doped graphene in an electro-Fenton system

Preferential promotion of the two-electron reduction reaction of dissolved oxygen by controlling the type and amount of doped nitrogen atoms.

Nitrogen-doped carbon nanotube supported double-shelled hollow composites for asymmetric supercapacitors

A double-shelled hollow structure N–C@NiMoO₄ composite was prepared taking N-doped carbon nanotubes as a skeleton, and exhibited high electrochemical performance for supercapacitors.

Heteroatom-Doped Carbon Nanotube and Graphene-Based Electrocatalysts for Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) is a key step that determines the performance of a variety of energy storage and conversion devices, such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanotubes (CNTs) and graphenes have attracted increasing interest and hold great promise as efficient ORR catalysts to replace noble-metal-based catalysts, owing to their unique structure characteristics, excellent physicochemical properties, low cost, and rich resources. In this review, recent progress on the design, fabrication, and performance of heteroatom-doped CNT- and graphene-based catalysts is summarized, aiming to provide insights into the working mechanism of these heteroatom-doped nanocarbons in ORR. The advantages, challenges that remain, and possible solutions of these nanocarbon-based electrocatalysts are discussed. Finally, future developing trends of the CNT- and graphene-based ORR catalysts are proposed.

Thermal Behavior and Spectroscopy Analysis of Carbonized Nanostructures Derived from Polypyrrole Nanotubes

Carbonaceous nanotubes with a calculated specific heat of 710[Formula: see text]J K[Formula: see text] Kg[Formula: see text], and an outer diameter of 58[Formula: see text]nm, made by a micro-thermal reaction, using polypyrrole nanotubes precursor is presented here. Three degradation stages from the thermal curves are identified. We observe a decomposition temperature at 371[Formula: see text]C that relates to the presence of amorphous carbon on samples for the first time in this material. Also, it is identified that gradual decomposition of the fragments provides a different kind of residue percentage in the range 48–32% that is related to stirring speed used in each synthesis. It is worthy to note that electron transmission microscope images of carbonaceous nanotubes present defects as well, wherein we identify chloride and nitrogen as doped agents. Finally, results of nanotubes using Infrared, Raman spectrometry analysis, scanning electron microscopy and electron diffraction are presented here.

Facile fabrication of N-doped hierarchical porous carbon@CNT coaxial nanocables with high performance for energy storage and conversion

N-Doped hierarchical porous carbon@CNT coaxial nanocables were facilely synthesized and demonstrated to be an ideal carbon nanostructure for electrochemical performance optimization for supercapacitors and in the oxygen reduction reaction.