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The development of efficient and cheap bifunctional catalysts for oxygen reduction and oxygen evolution reactions, is vital for the design of rechargeable Zn-air batteries. Herein, a facile strategy to fabricate Co/Co9S8 nanoparticles-encapsulated in carbon nanotubes, on an N-doped porous graphene sheet (Co/Co9S8@CNTs) via pyrolysis of a mixture of Co(NO3)2, melamine and L-cysteine is reported, the composition can be facile controlled using the molar ratio of melamine and L-cysteine. By controlling the molar ratio of melamine and L-cysteine and the pyrolysis temperature, Co/Co9S8@CNTs obtained at 900 °C (Co/Co9S8@CNTs-900) perform with high activities in oxygen reduction and oxygen evolution reactions, which promotes their application for rechargeable Zn-air batteries. Furthermore, the rechargeable Zn-air battery assembled with Co/Co9S8@CNTs-900 shows a high peak power density of 184.7 mW cm−2 and good long-term durability, holding great potential in practical applications.

Here, polyaniline (PANI) is reported loaded on carbon paper to modify the carbon paper-PANI-Pt electrode surface, tailoring the electrocatalytic capability towards the hydrogen evolution reaction and ethanol oxidation reaction. The reasons for the enhancement by the PANI layer are attributed to the hydrophilic electrode surface, uniform dispersion of Pt, and large electrochemical active surface.

Fe-Based electrocatalysts on carbon substrates are considered suitable candidates for applications in Zn–air batteries due to their favorable ORR performance. Herein, unique Fe3C@N-doped porous carbon nanorods have been synthesized using a soft template method and carbonization. The material proved to have a porous hetero-structure, which is advantageous in providing effective electrocatalysis performance for oxygen reduction reaction, providing broad prospects for the development of non-precious metal electrocatalysts and metal–air batteries. This catalyst used for oxygen reduction reaction exhibits a half-wave of 0.83 V, which is close to that of the commercial Pt/C catalyst. Using the as-prepared Fe3C@N-doped porous carbon nanorods, the open circuit potential and power density of a Zn–air battery has been measured as 1.42 V and 126.4 mW cm−2, respectively, which are better than those of the commercial Pt/C. This study presents a novel strategy to prepare Fe3C@N-doped porous carbon nanorods, which can be used as highly effective oxygen reduction reaction catalysts for Zn–air batteries.

Electrocatalysis caused by the crystallinity of catalysts is viewed as a key role of the electrocatalytic activity, but there are a few reports on it. Herein, we report the electrocatalytic activity depending on the crystallinity of Mo-doped Co3(PO4)2 (PiMoCo). A series of PiMoCo with different crystalline structures were controllably prepared via co-precipitation and heat treatment. The PiMoCos obtained at room temperature and 800 °C were crystalline, while those obtained at 300–500 °C were amorphous. The electrocatalysis of PiMoCo depended on their phase transformation, which can be controlled by the temperature of heat treatment. The electrochemical performances for oxygen evolution reaction show that the PiMoCos with the amorphous phase exhibit high activity and stability. This work provides an insight into the electrocatalysis performance depending on the crystallinity of catalysts and the water molecules in the lattice of PiMoCo.

Generally, polyacrylonitrile (PAN)-based hydrogels possessing excellent mechanical properties are prepared by water replacement after the copolymerization of acrylonitrile (AN) and other hydrophilic monomers in their good organic solvents. However, PAN-based hydrogels synthesized by the conventional strategy not only cause huge environmental problems but also inevitably lose their pristine mechanical properties at subzero temperatures, which severely limits their real-world applications. Here, we designed a novel PAN-based hydrogel under an aqueous system containing ZnCl2 salts without any toxic organic solvents. Based on the salt used in the polymerization strategy, P(AN-co-AMPS) hydrogels (AAHs) can be realized by direct co-polymerization of AN and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) in water in the presence of ZnCl2 salts. ZnCl2 serves three predominant functions: dissolving AN in water to conduct polymerization, inhibiting the formation of ice crystals to realize freeze-tolerance under extremely cold conditions and introducing free ions to promote the conductivity of the hydrogel. Consequently, the AAH simultaneously possesses long-term stability, excellent anti-freezing properties and a high conductivity of 1.16 S m−1 even at −50 °C. Moreover, we demonstrated the AAH as a wearable strain sensor, which features outstanding performance for monitoring different daily human activities in real time. This one-step aqueous-based approach for preparing anti-freezing and conductive PAN-based hydrogels may open a new avenue for the reliable construction of high-performance flexible sensors under environmentally friendly conditions.

Metal sulfides have been extensively studied as alternative anodes for lithium-ion batteries (LIBs) due to their high specific capacity, which comes from their combined conversion and alloying/de-alloying reactions with lithium, forming Li2S and corresponding lithium alloys, respectively. However, the large volume fluctuation during cycling, low electronic/ionic conductivities of both metal sulfides and Li2S, and the electrochemical inactivity of Li2S lead to poor reversibility and stability. Here, we report a facile way to synthesize a three-dimensional carbon-coated stannous sulfide-molybdenum disulfide composite (3D SnS–MoS2@C) which is proposed to alleviate the aforementioned problems. 3D SnS–MoS2@C exhibits a highly porous structure, which enhances the contact between the electrode and the electrolyte, promotes the transport of both electrons and Li+, and buffers the volume change during cycling. MoS2 contributes to the specific capacity and catalyzes the oxidation of Li2S. The 3D SnS–MoS2@C anode demonstrates a capacity of 887.1 mA h g−1 for the first cycle at 200 mA g−1 and achieves a capacity retention of 97.1% over 200 cycles. In addition, the ternary composite exhibits a superior rate performance and cycling lifespan, achieving a gravimetric capacity of 651.2 mA h g−1 at 1000 mA g−1 after 500 cycles. The proposed facile and effective strategy could be universally applied to other metal sulfide-based electrodes.

The synthesis of NH3 heavily relies on the Haber-Bosch process suffering from a large amount of CO2 emission and energy consumption. Possessing eco-friendly and sustainable characteristics, electrochemical reduction is considered as a promising candidate for artificial N2 fixation under ambient conditions, but efficient electrocatalysts are crucial for the N2 reduction reaction (NRR). In this communication, we report that perovskite La2Ti2O7 nanosheets behave as an efficient NRR electrocatalyst with excellent selectivity under ambient conditions. In 0.1 M HCl, this catalyst achieves a high NH3 yield rate of 25.15 μg h-1 mgcat.-1 with a faradaic efficiency of 4.55% at -0.55 V vs. a reversible hydrogen electrode. Notably, it also shows high electrochemical stability.

International audience; Many sulfide-based supercapacitors suffer from the problem of large capacity and energy attenuation at high rates. To tackle this problem, a strong magnetic field (SMF) was exerted twice during new material synthesis and electrode fabrication. Here, one-dimensional (1D) hetero-Zn0.76Co0.24S/Co3S4/β-CoS1.097 hollow sphere nanochains (CZ55S6T) were first prepared via a one-step anion-exchange reaction under SMF. The SMF-induced directional growth of paramagnetic Zn0.76Co0.24S in the outer shell contributed to the directional assembly of the simultaneously hollowing-out spheres into 1D nanochains based on the Kirkendall effect accelerated by SMF. Physicochemical investigations revealed that SMF endowed CZ55S6T with a larger surface area and reduced the loss of active components, especially Zn. The unique 1D hollow nanochain nanostructures contributed to a remarkable rate performance. An oriented CZ55S6T nanochains/graphene flake capacitive electrode (CZ55S6T/G) with high loading (∼8 mg cm−2) was further fabricated using SMF to reduce the path tortuosity. The CZ55S6T/G electrode exhibited strikingly enhanced rate capability with 80% capacitance retention (863.8 F g−1) and cycling capacitance (705 F g−1 after 5000 cycles) at a high rate of 20 A g−1. Furthermore, the CZ55S6T/G-based asymmetric supercapacitor delivered remarkable energy density of 51.5 W h kg−1 at a large power density of 6811 W kg−1.

Iron sulfides, as promising anode materials, have been intensively studied, but still encounter problems due to their limited cycle life caused by huge volume changes. In the present work, a facile method has been presented to prepare Fe2O3 nanobiscuits followed by poly(dopamine) coating. After thermally induced sulfurization, Fe7S8@C nanobiscuits have been successfully obtained, which show high specific capacities, excellent rate capabilities and stable cycling stability as anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). They exhibit high reversible capacities of 547.3 mA h g−1 after 600 cycles and 530.8 mA h g−1 after 1000 cycles at a high current density of 5 A g−1 for LIBs and SIBs, respectively. This outstanding electrochemical performance may be attributed to the stress-buffering effect owing to the biscuit-like nanostructure and conformal surface coating with carbon.

In order to understand the effects of chain length on the interfacial adhesion of PAN-based carbon fiber (CF)/epoxy composites, dendritic hexamethylenetetramine (HMTA) was functionalized on carbon fibers through quaternary ammonium salt reaction using alkyl dihalide of varying chain length [Cl(CH2)nCl, n = 2, 6 and 12]. Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS) confirmed the successful grafting of dendritic HMTA and alkyl dihalide. AFM images showed that dendritic HMTA modified CF surfaces enhanced roughness, and this effect was more pronounced with increasing alkyl dihalide chain length. The results of dynamic contact angle (DCA) and interfacial shear strength (IFSS) demonstrated that the surface energy and interfacial adhesion increased and then decreased with the chain length of alkyl dihalide. The tensile strength and impact roughness of the composites enhanced as the alkyl dihalide chain length grew. Moreover, the reinforcing and toughening mechanisms were also discussed.