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Water electrolysis is a promising approach for green and large-scale hydrogen production; however, there are still challenges for developing efficient and stable bifunctional electrocatalysts toward the hydrogen and oxygen evolution reactions. Herein, zeolitic imidazolate framework-67 was used as the precursor for the construction of CoSe2nanoparticles trapped in N-doped carbon (NC) polyhedra. Among as-obtained CoSe2-NC hybrid, highly active CoSe2nanoparticles in sizes of 10–20 nm are encapsulated in N-doped few-layer carbon shell, avoiding their easy aggregations of CoSe2nanoparticles as well as enhancing the long-term stability. The unique nanostructured CoSe2-NC hybrid with a hierarchical porosity and 3D conductive framework thus fully exerts outstanding bifunctional catalytic activity of CoSe2centers. As a result, the CoSe2-NC hybrid as bifunctional catalysts for overall water splitting delivers a high current density of 50 mA cm–2with an applied voltage of ∼1.73 V in an alkaline electrolyte, with a promising stability over 50 000 s.

Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of −0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER.

To remit energy crisis and environmental deterioration, non-noble metal nanocomposites have attracted extensive attention, acting as a fresh kind of cost-effective electrocatalysts for hydrogen evolution reaction (HER). In this work, hierarchically organized nitrogen-doped carbon nanofiber/molybdenum disulfide (pBC-N/MoS2) nanocomposites were successfully prepared via the combination of in situ polymerization, high-temperature carbonization process, and hydrothermal reaction. Attributing to the uniform coating of polyaniline on the surface of bacterial cellulose, the nitrogen-doped carbon nanofiber network acts as an excellent three-dimensional template for hydrothermal growth of MoS2nanosheets. The obtained hierarchical pBC-N/MoS2nanocomposites exhibit excellent electrocatalytic activity for HER with small overpotential of 108 mV, high current density of 8.7 mA cm–2at η = 200 mV, low Tafel slope of 61 mV dec–1, and even excellent stability. The greatly improved performance is benefiting from the highly exposed active edge sites of MoS2nanosheets, the intimate connection between MoS2nanosheets and the highly conductive nitrogen-doped carbon nanofibers and the three-dimensional networks thus formed. Therefore, this work provides a novel strategy for design and application of bacterial cellulose and MoS2-based nanocomposites as cost-effective HER eletrocatalysts.

The practical applications of transition-metal dichalcogenides for lithium-ion batteries are severely inhibited by their inferior structural stability and electrical conductivity, which can be solved by optimizing these materials to nanostructures and confining them within conductive frameworks. Thus, we report a facile approach to prepare flexible papers with SnS2nanosheets (SnS2NSs) homogeneously dispersed and confined within the conductive graphene-carbon nanotube (CNT) hybrid frameworks. The confinement of SnS2NSs in graphene-CNT matrixes not only can effectively prevent their aggregation during the discharge–charge procedure, but also can assist facilitating ion transfer across the interfaces. As a result, the optimized SGC papers give an improved capacity of 1118.2 mA h g–1at 0.1 A g–1along with outstanding stability. This report demonstrates the significance of employing graphene-CNT matrixes for confinement of various active materials to fabricate flexible electrode materials.

The practical applications of transition metal oxides and hydroxides for supercapacitors are restricted by their intrinsic poor conductivity, large volumetric expansion, and rapid capacitance fading upon cycling, which can be solved by optimizing these materials to nanostructures and confining them within conductive carbonaceous frameworks. In this work, flexible hybrid membranes with ultrathin Ni(OH)2nanoplatelets vertically and uniformly anchored on the electrospun carbon nanofibers (CNF) have been facilely prepared as electrode materials for supercapacitors. The Ni(OH)2/CNF hybrid membranes with three-dimensional macroporous architectures as well as hierarchical nanostructures can provide open and continuous channels for rapid diffusion of electrolyte to access the electrochemically active Ni(OH)2nanoplatelets. Moreover, the carbon nanofiber can act both as a conductive core to provide efficient transport of electrons for fast Faradaic redox reactions of the Ni(OH)2sheath, and as a buffering matrix to mitigate the local volumetric expansion/contraction upon long-term cycling. As a consequence, the optimized Ni(OH)2/CNF hybrid membrane exhibits a high specific capacitance of 2523 F g–1(based on the mass of Ni(OH)2, that is 701 F g–1based on the total mass) at a scan rate of 5 mV s–1. The Ni(OH)2/CNF hybrid membranes with high mechanical flexibility, superior electrical conductivity, and remarkably improved electrochemical capacitance are condsidered as promising flexible electrode materials for high-performance supercapacitors.

Assembling two-dimensional MXenes into 3D macroscopic structures is an applicable method to give full play to its excellent electrical and mechanical properties toward multi-functionality. Considering the weak interfacial interaction and poor gelation ability of MXenes, short polyimide nanofibers (PINFs) are utilized as cross-linking and supporting building blocks in this work to construct a lightweight, robust, and elastic PINF/Ti3C2TxMXene composite aerogel (PINF/MA) via a simple synergistic assembly strategy. Taking advantage of its unique 3D “lamella-pillar” microporous architecture, the designed PINF/MA composite aerogel exhibits excellent piezoresistive sensing performance in terms of a wide pressure range of 0–8 kPa (50% strain), a high piezoresistive sensitivity of 22.32 kPa–1, an ultra-low detection limit of 0.1% strain, and great compression/rebound stability (signal remained stable after 1500 cycles). These remarkable piezoresistive sensing properties enable the PINF/MA with intriguing capability to detect small and large human activities in real time (wrist and finger bending, pulse, and vocal cord vibration). More interestingly, the parallelly aligned leaf vein-like lamellae also empower the PINF/MA with prominent wave absorption performance [RLminis −40.45 dB at 15.19 GHz, with an effective absorption bandwidth of 5.66 GHz (12.34–18 GHz)], making the multi-functional PINF/MA composite aerogels promising candidates for wearable strain sensors and microwave absorbers.