Metal-organic framework (MOF)-derived functional carbon matrices have recently attracted considerable attention as energy-storage materials. However, the development of MOF-derived carbon materials with hierarchical structures, capable of thoroughly preventing the "shuttling" of polysulfides, is still a major challenge. Herein, we synthesized cobalt nanoparticle-containing porous carbon polyhedra with in situ grown N-doped carbon nanotube (CNT) backbone (NCCNT-Co), using zeolitic imidazolate framework-67 (ZIF-67) as starting material. The obtained NCCNT-Co, with interconnected N-doped CNTs on both inner and outer surfaces, possesses an integrated conductive network, which can further accelerate the transport of electrons/ions inside the whole sulfur cathode. The mesoporous structure derived from the ZIF-67 matrix and the densely immobilized CNTs, coupled with the homogeneously doped N atoms and Co nanoparticles, can efficiently trap lithium polysulfides (LiPSs) by physical confinement and chemical interactions. Furthermore, the hierarchical structure of the porous carbon polyhedra enables a high sulfur loading of up to 76 wt.% and can also buffer the volume changes of active sulfur during the lithiation process. As a result, the NCCNT-Co-S cathode delivers a high initial specific capacity of 1, 300 mAh·g^-1 at 0.1 C, along with a high capacity of 860 mAh·g^-1 after 500 cycles at 1 C, with an extremely low capacity decay of 0.024% per cycle.

The development of highly active and cost-effective hydrogen evolution reaction (HER) catalysts is of vital importance to addressing global energy issues. Here, a three-dimensional interconnected porous carbon nanofiber (PCNF) membrane has been developed and utilized as a support for active cobalt phosphide (CoP) nanoparticles. This rationally designed self-supported HER catalyst has a lotus root-like multichannel structure, which provides several intrinsic advantages over conventional CNFs. The longitudinal channels can store the electrolyte and ensure fast ion and mass transport within the catalysts. Additionally, mesopores on the outer and inner carbon walls enhance ion and mass migration of the electrolyte to HER active CoP nanoparticles, thus shortening the ion transport distance and increasing the contact area between the electrolyte and the CoP nanoparticles. Moreover, the conductive carbon substrate provides fast electron transfer pathways by forming an integrated conductive network, which further ensures fast HER kinetics. As a result, the CoP/PCNF composites exhibit low onset-potentials (?20, ?91, and?84 mV in 0.5 M H₂SO₄, 1 M PBS, and 1 M KOH, respectively). These findings show that CoP/PCNF composites are promising self-supporting and high-performance all-pH range HER catalysts.

Benefiting from their unique delocalized electronic structure, conjugated polymer-based semiconductors are widely applied in the fields of organic electronics, sensors, and biomedical applications. However, the photocatalytic properties of conjugated polymers have been seldom studied because of their unsuitable band structures. Herein, we creatively demonstrate that the band structures of conjugated polymers are strongly related to their degree of polymerization (DP), offering an effective strategy for the design of metal-free photocatalysts with tunable light absorption properties. Taking poly(3-hexylthiophene) (PHT) as an example, we show that PHT nanofibers with a suitable DP are a novel visible light-driven photocatalyst, which can readily convert molecular oxygen into superoxide ions. Benefiting from the high selectivity of the generated superoxides, the PHT nanofibers display outstanding activity for the aerobic oxidation of amines into imines with nearly 100% conversion and selectivity. This study offers a new strategy for the design of advanced conjugated polymer-based photocatalysts.

The soluble nature of polysulfide species created on the sulfur electrode has severely hampered the electrochemical performance of lithium–sulfur (Li–S) batteries. Trapping and anchoring polysulfides are promising approaches for overcoming this issue. In this work, a mechanically robust, electrically conductive hybrid carbon aerogel (HCA) with aligned and interconnected pores was created and investigated as an interlayer for Li–S batteries. The hierarchical cross-linked networks constructed by graphene sheets and carbon nanotubes can act as an "internet" to capture the polysulfide, while the microand nano-pores inside the aerogel can facilitate quick penetration of the electrolyte and rapid transport of lithium ions. As advantages of the unique structure and excellent accommodation of the volume change of the active materials, a high specific capacity of 1, 309 mAh·g^-1 at 0.2 C was achieved for the assembled Li–S battery, coupled with good rate performance and long-term cycling stability (78% capacity retention after 600 cycles at 4 C).

NiS nanoparticles (NPs) with excellent electrochemical capacitance have attracted considerable attention as cost-effective energy-storage materials for supercapacitors in recent years. Preventing the aggregation and increasing the conductivity of NiS NPs are key to fully realizing their excellent electrochemical properties. In this work, NiS/N-doped carbon fiber aerogel (N-CFA) nanocomposites were obtained easily through the combination of polymerization, carbonization, and a one-step solvothermal reaction. N-CFA derived from polydopamine (PDA)-coated cotton wool was used as a template for the construction of hierarchical NiS/N-CFA nanocomposites, in which NiS NPs are uniformly immobilized on the surface of N-CFA. In this nanostructured system, N-CFA containing abundant nanofibers not only provides active regions for the growth of NiS NPs to prevent their aggregation, but also offers short pathways for the transport of electrons and ions. The electrochemical properties of the obtained NiS/N-CFA nanocomposites were investigated by cyclic voltammetry, galvanostatic charge–discharge, and alternating current impedance measurements. The optimized NiS/N-CFA nanocomposite exhibits a high specific capacitance of 1, 612.5 F·g^-1 at a charge/discharge current density of 1 A·g^-1 and excellent rate capacitance retention of 66.7% at 20 A·g^-1. The excellent electrochemical properties of NiS/N-CFA nanocomposites make these materials promising electrode materials for supercapacitors.

In this study, macroscopic graphene-wrapped melamine foams (MF-G) were fabricated by an MF-templated layer-by-layer (LBL) assembly using graphene oxide as building blocks, followed by solution-processed reduction. By concisely duplicating sponge-like, highly ordered three-dimensional architectures from MF, the resulting MF-G with an interconnected graphene-based scaffold and tunable nanostructure was explored as compressible, robust electrodes for efficient energy storage. A thin layer of pseudocapacitive polypyrrole (PPy) was then attached and uniformly coated on MF-G, resulting in a well-defined core–double-shell configuration of the MF-G-PPy ternary composite sponges. The as-assembled devices exhibited enhancement of supercapacitor performance, with a high specific capacitance of 427 F·g^-1 under a compressive strain of 75% and an excellent cycling stability with only 18% degradation after 5, 000 charge–discharge cycles. Besides, the MF-G-PPy electrode maintained stable capacitance up to 100 compression–release cycles, with a compressive strain of 75%. These encouraging results thus provide a new route towards the low-cost, easily scalable fabrication of lightweight and deformation-tolerant electrodes.