Amorphous Carbon Shell Research Articles

Seed-Assisted Hydrothermal Synthesis of Monodispersed Au@C Core–Shell Nanostructures for Enhancing Thermal Diffusivity of Water-Based Nanofluids

Au@C core–shell nanostructures (Au@C-NS) were synthesized through a low-temperature seed-assisted hydrothermal approach using glucose as carbon source. The material characterization and chemical analysis confirm that the synthesis method allows to obtain uniform core–shell nanostructures constituted by a crystalline metal core and an amorphous carbon shell. Depending on the synthesis conditions, their average size ranges from 146 nm to 342 nm with relative standard deviation as low as 7 %. It is proposed that the characteristic monodispersity results due to a high nucleation rate of the carbon phase at the liquid–solid interface. The obtained monodisperse Au@C-NS were used to prepare water-based nanofluids with superior heat transport properties. The thermal lens analysis shows that the thermal diffusivity of Au@C nanofluids is 9.5 % and 31.3 % higher than their Au nanofluids counterparts and pure water, respectively, at particle concentration of 285 × 1011 ml−1. Phonon-related interactions at the metal cores and carbon shells interfaces are proposed as the heat transport mechanism behind the thermal diffusivity enhancement of the Au@C water-based nanofluids.

Room Temperature Synthesis of Tellurium by Solution Atomic Layer Deposition.

This study demonstrates the deposition of tellurium (Te) on silicon/silicon nitride substrates using solution atomic layer deposition (sALD) at ambient temperature. The process employs tellurium tetrachloride (TeCl4) and bis(triethylsilyl)-telluride ((TES)2Te) as precursors, with toluene as the solvent. Growth parameters were optimized through systematic variation of the pulse and purge times. Morphological characterization via scanning and transmission electron microscopy revealed needle-like crystallites, while X-ray diffractometry confirmed the crystalline nature of the deposited Te. Increasing the number of deposition cycles resulted in larger Te crystallites and enhanced substrate surface coverage. A thin amorphous carbon shell surrounding the crystallites and carbon inclusions was observed, likely originating from the organic solvent. X-ray photoemission spectroscopy analysis indicated high-purity Te films with minimal surface oxidation. The small chlorine signal suggested a near-complete precursor reaction and the efficient purging of byproducts. This novel sALD approach presents a promising method for depositing Te on various surfaces under mild conditions.

Facile synthesis of nano-si/graphite-carbon anode through microwave-induced carbothermal shock for lithium-ion batteries

We present a cost-effective synthesis process for producing a carbon-coated nano-Si@Graphite (n-Si@G-C) anode, in which nano-sized Si (n-Si) particles (∼50 nm in size) are anchored onto natural graphite particles by a carbothermal shock through microwave induction. During the carbothermal shock process, graphite undergoes a fast increase in temperature resulting in micron-sized Si (m-Si) particles (∼4 μm in size) to undergo stress fractures due to rapid thermal expansion. This process leads to the formation of abundant n-Si particles onto graphite particles. Subsequently, a thin carbon shell is introduced by a wet-coating process combined with a thermal decomposition of coal-tar pitch. The amorphous carbon shell offers multiple functionalities: i) preventing direct exposure of n-Si particles to the electrolyte, ii) accommodating their volume expansion, and iii) maintaining electron conduction pathways. The resulting n-Si@G-C anode allows a high reversible capacity (500.8 mAh g−1) as well as fast-charging characteristics. When utilized in a full-cell configured with a commercial-grade LiNi0.8Co0.1Mn0.1O2 cathode, it achieves a notable reduction in charging time (approximately 10.1 min@80 % state of charge). After 300 cycles, a high capacity retention (71.3 %) can be retained under 3C charging. Moreover, the distinctive structural features of the n-Si@G-C anode effectively suppress undesirable Li plating.

Preparation and anti-oxidation performance of TaC-SiC nanocomposites by precursor-derived ceramic method

As a kind of ultra-high temperature ceramic, TaC is widely used in aerospace field. In order to improve its high temperature oxidation resistance, SiC is usually added as a second phase. TaC-SiC nanocomposites prepared by precursor-derived ceramic method have the advantages of low pyrolysis temperature, small particle size and uniform phase composition. Some studies have used solid polycarbosilane (PCS) as the precursor of SiC. However, it has problems such as high cost and need to add solvent. In this work, TaC-SiC nanocomposites were prepared by precursor-derived ceramic method with polytantaloxane (PTO) and vinyl-containing liquid polycarbosilane (LPVCS) instead of PCS as raw materials after 2 h pyrolysis at 1600 °C. The obtained TaC-SiC nanocomposites have a particle size of about 200 nm and a grain size of 15–40 nm, wrapped by 1–2 nm amorphous carbon shells, which is beneficial to inhibit grain growth. By analyzing the oxidation mechanism of TaC-SiC nanocomposites, it was found that higher SiC content was conducive to antioxidant, because the SiO2 protective layer formed by oxidation insulated O2 diffusion.

Purification of carbon nanotubes for dissolution in chlorosulfonic acid

Carbon nanotubes (CNTs) can be scalably processed into high-performance fiber with a low environmental footprint by solution spinning from chlorosulfonic acid (CSA). CNTs are produced by numerous manufacturers, but CNTs typically need to undergo purification to improve solubility in CSA. For over two decades, oxidative techniques have been used to remove amorphous carbon species to improve CNT dissolution in acid. However, more recent work has attributed the improved solubility after single-walled carbon nanotube (SWCNT) oxidation to the inclusion of oxygen groups in the sidewall of the SWCNT. Here, we refute the recent claim that oxidation incorporates oxygen into the sidewall of CNTs to improve CNT dissolution to CSA. Instead, we provide experimental evidence in support of classical purification literature: at the appropriate time and temperature, oxidation removes amorphous carbon shells and defective SWCNTs without oxidizing the SWCNT sidewall. Once these amorphous carbon shells are removed, CSA can access and protonate the sp2-bonded carbon sites, which results in SWCNT dissolution. Additionally, we explore how oxidation conditions impact SWCNT aspect ratio (length of CNT divided by CNT diameter), which directly controls macroscale fiber properties.

Debundling and reorganization of CNT networks under high temperature treatment

Highly purified and uniformly distributed carbon nanotube (CNT) network is one of the key issues for developing advanced nanocomposites. However, the challenge for mitigation of the aggregation of CNT bundles during the CNT film fabrication still remained. In this work, debundling and reorganization of CNT bundles have been realized simultaneously by using a high-temperature thermal treatment. The debundling of large CNT bundles into small ones started after they were heat treated under 1400 °C and uniformly distributed CNT networks with small bundles were obtained after heat treated under 1800 °C. The tensile strength of the CNT film significantly increased by about 64% compared to the pristine film. Microstructural observations showed that the iron nanoparticles started to evaporate at 1400 °C and were completely removed at 1800 °C. Hollow amorphous carbon shells wrapped on the nanoparticles were left inside the CNT networks after the removal of the iron nanoparticles. Interestingly, these amorphous carbon shells act as carbon source for the deposition of a carbon layer on the CNT surface when the heat treatment temperature was up to 2000 °C, and they were completely consumed after being treated at 2800 °C. The microstructural evolution process of CNT bundles during heat treatment suggests the simple high-temperature treatment strategy could be applied for fabrication of highly purified CNT networks with well-distributed small bundles, enabling the development of advanced multifunctional nanocomposites in the near future.

Enhanced mechanical and tribological properties of low-cost core-shell structured microcrystalline graphite/Cu composites

In the past, microcrystalline graphite (MG) was mainly used for the preparation of carbon enhancers and flame retardant, and is a low value-added inorganic mineral. There are very few reports of MG being compounded with Cu to produce friction materials. Carbon coated microcrystalline graphite/Cu (Carbon@MG/Cu) composites were prepared by coating MG with phenolic resin and mixing it with Cu. The effect of the phenolic resin coating on the mechanical and tribological properties of the composites was investigated by comparison with pure Cu, microcrystalline graphite/Cu (MG/Cu). The hardness and flexural strength of pure Cu were 39.8 HV and 72.3 MPa, respectively. The protection of the amorphous carbon shells led to a significant improvement in the mechanical properties of Carbon@MG/Cu, with hardness and flexural strengths of 72.3 HV and 103.8 MPa. The poor bonding between the MG and Cu severely affects its mechanical properties. Pure Cu has the highest wear rate (10.6 × 10−7(mm3/(N∙m)), while Carbon@MG/Cu has a stable coefficient of friction (0.19) and the lowest wear rate (4.3 × 10−7 (mm3/(N∙m)) compared to pure Cu and MG/Cu. We provide a method to prepare graphite/Cu composites with high mechanical and tribological properties based on low-cost MG, which helps to solve the problem of reuse of MG and increase its industrial added value.

Design of rich defects carbon coated MnFe2O4/LaMnO3/LaFeO3 heterostructure nanocomposites for broadband electromagnetic wave absorption

The precise construction of abundant heterointerfaces and defects in manganese ferrite for efficient electromagnetic wave (EMW) absorption is highly appealing, yet remains a grand challenge. Herein, we report a class of carbon-coated MnFe2O4/LaMnO3/LaFeO3 heterostructure nanocomposites with foam-like porous structures for enhancing EMW absorption. The optimized sample (the molar ratio of Mn:Fe:La is 1:2:1) delivers extraordinary absorption performance of the minimum reflection loss reaches −68.25 dB at 4.24 GHz, along with the maximum effective absorption (RL ≤ -10 dB) bandwidth is 12.26 GHz (3.11–15.37 GHz) at a thickness of 3.9 mm. EMW absorption mechanism reveals that the multiple polarizations induced by adjustable heterointerfaces and abundant defects in spinel/perovskite nanocomposites enhance its dielectric loss capacity, resulting in impressive EMW absorption performance. Moreover, the amorphous carbon shell further optimizes impedance matching. This study not only provides a good reference for future preparation of microwave absorbing materials with rich heterogeneous interfaces and defects but also broadens the application of such kinds of carbon-coated spinel/perovskite nanocomposites.

Encapsulated prussian blue analogs derived nanocubes with tunable yolk-shell structure enabling highly efficient microwave absorption

Pyrolytic Prussian blue analogs (PBAs) have attracted much attention in the field of microwave absorption (MA) because of their outstanding magnetic-carbon synergism effect. However, pure PBAs are prone to collapse and aggregate during pyrolysis, resulting in impedance mismatch that weaken the MA performance. Herein, the amorphous carbon layer with adjustable dielectric constant as the encapsulated layer, together with pyrolytic PBAs enables remarkable optimized performance via forming the classic yolk-shell structure. Specifically, the amorphous carbon obtained by quantitatively carbonizing phenolic resin, can not only avoid the collapse of pyrolytic PBAs but also optimize electromagnetic parameters to achieve optimum impedance matching by varying thickness. The NiFe alloys/graphite carbon core derived from pyrolytic NiFe–PBAs also enhance synergistic attenuation in the YS-NiFe/GC@C absorbers. According to experimental results, all YS-NiFe/GC@C absorbers exhibit impressive MA properties. When the thickness of the amorphous carbon shell is 50 nm, the minimum reflection loss value is as low as −56.3 dB and the maximum effective absorption bandwidth reaches 5.64 GHz, indicating that optimizing impedance matching via hierarchical and quantitative design can maximize the MA capability. The result is then verified by simulation calculations. Therefore, this promising work provides guidance for the sophisticated construction of tunable PBA-based MA materials.

Crack‐Induced Superelastic, Strength‐Tunable Carbon Nanotube Sponges

AbstractLightweight strong aerogels have many applications, but they suffer from the trade‐off between key mechanical properties, and it remains challenging to realize superelastic aerogels simultaneously possessing high strength and excellent structural recovery. Herein, a strategy to overcome such a problem by designing a carbon nanotube (CNT)‐based aerogel consisting of flexible‐rigid core‐shell structure, which achieve a combination of excellent properties including superelasticity (complete recovery at 90%), high strength (over 12 MPa at 90%) and wide tunability (from 101 kPa to 4.5 MPa at 50% strain), is presented. It is found that the outer rigid but brittle amorphous carbon shells crosslink the CNT cores and crack into orderly distributed segments during the first compression cycle, while the flexible CNT cores ensure the integrity of the overall skeleton and tolerance to large deformation. This designed CNT composite sponges exhibit overall superior mechanical properties than previously reported foams/aerogels, and due to such unique crack‐induced superelasticity mechanism, potential applications such as pressure sensors with wide‐range tailored sensitivity and high‐performance energy absorbers have been developed. This flexible‐rigid core‐shell synergia may provide further insight for tunable high‐strength aerogel design and innovative applications.

Hierarchical Structure Carbon-Coated CoNi Nanocatalysts Derived from Flower-Like Bimetal MOFs: Enhancing the Hydrogen Storage Performance of MgH2 under Mild Conditions

The construction of transition metal nanocatalysts has become an attractive way to improve the hydrogen storage performance of MgH2. However, it is still a great challenge to obtain multielement transition metal nanocatalysts, improve the hydrogen storage capacity of MgH2 under mild conditions (<573 K), and reduce the apparent activation energy of hydrogen absorption and desorption. In this work, a flower-like CoNi-MOF was successfully synthesized by sacrificing templates. After further pyrolysis, we obtained hierarchical structure flower-like MOF derivatives assembled by CoNi@C nanoparticles with an average particle size of 15.1 nm. Then, MgH2-x wt % CoNi@C nanocomposites are fabricated through the ball milling process. Due to the unique hierarchical flower-like structure of MOF derivatives, the inhibition of an amorphous carbon shell on CoNi alloy growth and agglomeration, and the synergistic catalysis of Mg2Co and Mg2Ni, the MgH2-10 wt % CoNi@C nanocomposite exhibits excellent hydrogen storage capacity under mild conditions and low apparent activation energy: At 473 K, the nanocomposite can quickly absorb 5.0 wt % H2 in 5 min, and even at 373 K, it can still absorb 4.2 wt % H2 in 60 min. At 573 and 548 K, it can release 4.8 and 3.1 wt % H2, respectively. The apparent activation energies for hydrogen absorption and desorption decrease remarkably to 24.9 and 67.3 kJ/mol, respectively, which are significantly better than those for MgH2-10 wt % Co@C (44.7 and 79.8 kJ/mol) and MgH2-10 wt % Ni@C (39.0 and 78.9 kJ/mol) nanocomposites. The first-principles calculation indicated that the hydrogen adsorption energy of the Mg–CoNi model is as low as −5.87 eV. This work provides a new strategy for the design of highly efficient multielement transition metal hydrogen storage material catalysts with a hierarchical structure.

Adsorption of organic dyes by Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@C, Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@C@C, Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@SiO&lt;sub&gt;2&lt;/sub&gt; magnetic nanoparticles

The Fe3O4@C, Fe3O4@C@C, and Fe3O4@SiO2 core-shell nanoparticles were synthesized using thermal decomposition and co-precipitation techniques and characterized by X-ray spectroscopy, transmission electron microscopy and magnetometry. It is shown that the magnetic core of all nanoparticles is nanocrystalline with crystal parameters corresponding to only one Fe3O4 phase, which is covered with a uniform shell of amorphous carbon or silicon oxide about 8 nm thick. The main attention was paid to the adsorption properties of nanoparticles with respect to four dyes: methylene blue, Congo red, eosin Y, and rhodamine C. The high selectivity of Fe3O4@C nanoparticles with respect to various dyes was revealed.

Modified preparation of Si@C@TiO2 porous microspheres as anodes for high-performance lithium-ion batteries.

Microscale porous silicon materials have shown great application potential as anodes for next-generation lithium-ion batteries (LIBs); however, they face significant challenges, including mechanical structure instability, low intrinsic conductivity, and uncontrollable processing. In this study, a modified etching strategy combined with a facile sol-gel method is demonstrated to prepare microscale porous Si microspheres encapsulated by an inner amorphous carbon shell (≈10 nm) and an outer rigid anatase titanium oxide (TiO2) shell (≈20 nm) (PSi@C@TiO2), with the intact porous framework and core-shell-shell spherical structure. The interconnected pores can sufficiently accommodate the expansion of the Si core during lithiation. Moreover, the double shells can not only enhance the kinetic behavior of the PSi@C@TiO2 microspheres, but can act as a compact fence to force the Si core to expand toward the internal pores during lithiation, ensuring the integrity of the porous spherical structure. As a result, the PSi@C@TiO2 anodes show greatly superior high specific capacity, excellent rate capability, stable solid-electrolyte interphase (SEI) films and steady mechanical structure. It delivers a high reversible capacity of 1004 mA h g-1 after 250 cycles at 0.5 A g-1. This study provides a modified method to prepare microscale porous Si anodes with a stable mechanical structure and long cycle life for LIBs.

In situ self-catalyzed formation of carbon nanotube wrapped and amorphous nanocarbon shell coated LiFePO4 microclew for high-power lithium ion batteries

A novel in situ self-catalyzed synthetic strategy is explored to prepare graphitic carbon nanotubes (CNTs) wrapped and amorphous nanocarbon shells coated LiFePO4 microclews (LiFePO4@C@CNT) at one-step. The formation mechanism of CNTs entangled LiFePO4@C microclews is investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that the in situ intergrowths of CNTs and LiFePO4@C could be realized by the catalytic effect of Fe3C nanoparticles based on the tip-growth mechanism. The as-prepared LiFePO4@C@CNT-5 composite with a low carbon content of 5 wt%, an optimum composition of graphitic CNTs and amorphous carbon shells (ID/IG = 0.9), a specific surface area of 83 m2 g−1 and an electronic/ionic conductivity of 0.68 S cm−1/2.1 × 10−12 cm2 s−1 delivers a stable discharge capacity of 158.2 mAh g−1 at 0.1 C, outstanding rate capability of 136.1 mAh g−1 at 1 C and remarkable long-term cycling stability of 129.6 mAh g−1 after 1000 cycles at 1 C, indicating a promising application in high-power lithium-ion batteries. The combined good electronic-ionic conductivity of twisted carbon nanotubes and porous nanocarbon shells and robust mechanical stability of geometrically confined LiFePO4 particles within dual nanocarbon matrices contribute to the excellent electrochemical performance of LiFePO4@C@CNT.

Controlled synthesis of Fe3O4 microparticles with interconnected 3D network structures for high-performance flexible solid-state asymmetric supercapacitors

The eco-friendly Fe-based oxides have attracted broad attention in supercapacitors on account of large theoretical capacities and cost-effective technologies associated with production and recycling. However, inferior conductivity and bad structural stability are still the main obstacles for its promoted application than the competition. In this work, well-designed Fe 3 O 4 microparticles with homogeneous size distribution, high crystallinity, and amorphous carbon shell have been synthesized and deposited on carbon fabric as an anode electrode via a series of feasible techniques, including anodic electrodeposition, polymerization, and annealing. The interconnected 3D network structures of electroactive materials are featured by high specific surface area and fast diffusion rate of ions. The sufacial carbon layer of Fe 3 O 4 particles, serves as the armor, which not only boosts electrical conductivity, but also maintains structural stability of the electrode during electrochemical processes. The electrochemical results show that the binder-free anode exhibits a remarkable areal capacitance of 0.95 F·cm −2 , a wide potential window of 1.2 V, and an outstanding cycling stability in 1 M KOH electrolyte (capacitance retention of 93.39 % over 8000 charge-discharge cycles). After combining with a NiCo-based cathode, 4.93 F·cm −3 volumetric capacitance, 1.8 mWh·cm −3 energy density, and 198 mW·cm −3 power density are achieved for the flexible solid-state asymmetric supercapacitor, which displays impressive cycling stability, excellent mechanical flexibility, and obvious performance advantages as compared with previously reported flexible energy storage devices. This work provides a feasible strategy to design a flexible Fe-based anode with superior conductivity and long-term stability for high-performing flexible solid-state asymmetric supercapacitor towards practical applications. • High crystallinity Fe 3 O 4 microparticles were deposited on CF via stepwise strategy. • Polypyrrole was served as carbon source and barrier material during annealing. • The 3D network structures embrace good conductivity and fast diffusion rate. • The anode exhibits large capacitance, wide potential window and good stability. • Bending test and 8000 GCD cycles demonstrate the flexibility and cycling stability.

Ni3Fe nanoparticles encapsulated by N-doped carbon derived from MOFs for oxygen evolution reaction

It has been a hot research topic to look for inexpensive alternative oxygen evolution reaction (OER) catalysts to replace noble metal-based materials due to their scarcity. Transition metals are ideal candidates because of their high abundance, impressive activities, and easy accessibility. However, a facile method leading to improved performance and stability is still needed. Herein, a highly efficient carbon-encapsulated bimetal catalyst derived from Ni-based metal-organic-frameworks (MOF) was successfully prepared through the low-temperature (350 ℃) pyrolysis of Prussian blue analogue (PBA) precursors under H 2 /Ar atmosphere. Cube-structured PBA as template and precursor，parameters during the pyrolysis process including temperature and calcination atmosphere can be tuned to control the structure and properties of the catalysts. Benefiting from the porous three-dimensional (3D) cubic structure and abundant defect-rich amorphous N-doped carbon shell, Ni 3 Fe@NC-350 exhibits excellent OER activity. The as-prepared catalysts exhibited excellent catalytic performance for OER in 1.0 M KOH with an overpotential of 237 mV to achieve 10 mA cm −2 . More importantly, the presented catalyst has an extremely good durability. • A simple low-temperature annealing method was developed to produce alloy encapsulated with N-doping carbon. • The NiFe PBA was employed as nitrogen and carbon source. • The increased activity of OER is due to the synergy of Ni 3 Fe alloy and N-doped carbon layer. • Theoretical calculations revealed that the synergistic effect of NiFe alloy nanoparticles and N-doped carbon layer.

Plasma-induced amorphous N-nano carbon shell for improving structural stability of LiNi0.8Co0.1Mn0.1O2 cathode

LiNi0.8Co0.1Mn0.1O2 (NCM) materials, which have a high specific capacity and low cost, suffer from large capacity attenuation and poor cycling performance in lithium-ion batteries. It is a straightforward and efficient strategy to elevate cyclic stability by building a stable surface coating to act as a valid physical or chemical barrier. In this study, N-doped carbon-coated active material NCM-N2 was successfully prepared by plasma-enhanced chemical vapor deposition (PECVD) in the N2 atmosphere. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical methods were used to study composition, structure, surface properties, and electrochemical properties. The coated NCM-N2 maintained good cycling performance (210.2 mAh g–1 at 0.1 C after 40 cycles, 188.5 mAh g–1 at 1 C after 100 cycles) and rate ability (131.7 mAh g–1 at 5 C rate). In comparison, the uncoated (NCM) electrode retained only 56.60% of its capacity (102.5 mAh g–1 at 1C after 100 cycles). The plasma-induced amorphous N-nano carbon shell on the surface of NCM effectively isolated the electrode from the electrolyte vastly inhibiting the occurrence of side reactions and was beneficial to the improvement of electronic conductivity. The plasma-induced amorphous N-nano carbon shell has great potential for enhancing the structural stability of Ni-rich ternary cathode materials, with broad application prospects in the Lithium-ion battery industry.

Molybdenum-vanadium diboride core @ amorphous nanoporous carbon shell composite as a novel electrode material for hybrid supercapacitor

Transition metal borides (TMB) are among one of the brightest prospects for aqueous supercapacitor due to their extraordinary capacitive performances. However, majority of the reported TMBs to date are amorphous, which slows the electron transfer and can even disrupt the structure during cycling. Herein, we report, grain boundaries enriched molybdenum‑vanadium diboride in a carbon matrix (Mo-V-B2@C) possessing well-defined amorphous shell with crystalline core morphology, synthesized by novel and controlled approach. The crystalline Mo-V-B2 in this structure facilitates ion diffusion and optimizes electronic conductivity, while nanoporous carbon maintains the structure's stability, resulting in a high specific capacitance (2368 F g−1 at 4 A g−1 in 1 M H2SO4), remarkable rate performance (1620 F g−1 at 20 A g−1), and outstanding cycling stability (142 % retention after 10,000 GCD cycles). Grain boundaries generate strained regions acting as active sites in the nanostructure for boosted charge storage characteristics. The Mo-V-B2@C||Mo-V-B2@C symmetric cell exhibits enhanced specific capacitance (512 F g−1 @ 1 A g−1), excellent cycling stability (125 % after 10,000 GCD cycles) with high energy/power density (65.1 W h kg−1 and 471.7 W kg−1). Such an effective novel approach throws new light on the synthesis and application of TMBs and similar charge storage materials with augmented grain boundaries for energy storage applications.

Synergistic coupling of amorphous carbon and graphitic domains toward high-rate and long-life K+ storage

Amorphous carbon materials hold great potential for practical use in potassium-ion batteries (PIBs) due to their abundant resources, low cost and high structural stability. However, given the challenge of sluggish potassiation kinetics, the rate performance of amorphous carbon is severely hindered. Herein, amorphous carbon compounded with graphitic domains (HG-CNTs) was proposed as an advanced anode for PIBs. As directly verified by in situ transmission electron microscopy (TEM), the graphitic domains guarantee fast K-ions transport in the carbon composite at a high current density, while the amorphous carbon shells ensure the structural integrity during potassiation, thus boosting its fast and durable K+ storage. As a PIB anode, the HG-CNTs electrode exhibits not only a super-stable long-term cyclability (191.6 mAh g−1 at 1 A g−1 with almost no capacity decay over 3000 cycles), but also an outstanding rate performance (184.5 mAh g−1 at 2 A g−1). Ex situ Raman and TEM results further suggest that the highly reversible structure of HG-CNTs is responsible for its superior electrochemical stability. This work provides helpful insights into the development of carbonaceous electrodes with both high rate capability and long cycle life for PIBs.

The High Electrocatalytic Performance of NiFeSe/CFP for Hydrogen Evolution Reaction Derived from a Prussian Blue Analogue

Non-noble-metal-based chalcogenides are promising candidates for hydrogen evolution reaction (HER) by harnessing the architectural design and the synergistic effect between the elements. Herein, a porous bimetallic selenide (NiFeSe) nanocube deposited on carbon fiber paper (NiFeSe/CFP) was synthesized through a facile selenization reaction based on Prussian blue analogues (PBAs) as precursors. The NiFeSe/CFP exhibited excellent HER activity with an overpotential of just 186 mV for a current density of 10 mA cm−2 in 1.0 M KOH at ambient temperature, similar to most of the state-of-the-art transition metal chalcogenides. The corresponding Tafel slope was calculated to be 52 mV dec−1, indicating fast discharge of the proton during the HER. Furthermore, the catalyst could endure long-term catalytic tests and showed remarkable durability. The enhanced electrocatalytic performance of NiFeSe/CFP is attributed to the unique 3D porous configuration inherited from the PBA templates, enhanced charge transfer occurring at the heterogeneous interface due to the synergistic effect between the bimetallic phases, and the high conductivity improved by the formation of amorphous carbon shells during the selenization. These findings prove that the combination of inexpensive metal–organic framework precursors and hybrid metallic compounds is a feasible way to realize the performance enhancement of non-noble-metal-based chalcogenides towards alkaline HER.