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Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide (MoP) is theoretically capable of efficient hydrogen evolution reaction (HER) catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon (MoP@NPCNFs) to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.

The rational construction of non-precious metals with carbonaceous material has attracted tremendous research attention with the aim to reduce the plethoric cost of platinum for catalyzing the oxygen reduction reaction (ORR). Herein, we synthesized a highly hierarchical nanostructure framework containing metal-carbon nanotubes anchored in metal embedded porous carbon spheres (M-CNTFs) and found it has similar ORR performance to that of commercial Pt-based electrocatalysts. Based on the unique hierarchical architecture, an effective platform was constructed to explore physic-chemical insights while providing guidance to search high-efficient ORR catalysts. Electrochemical measurements show that Co-CNTFs, Fe 3 C-CNTFs, and Ni-CNTFs prefer to proceed through a 4e - pathway, 2e - and 4e - mixed pathways, and a 2e - pathway, respectively. Furthermore, Co-CNTFs were found to perform better than a commercial Pt-based electrocatalyst in ORR due to its lower overpotential, excellent methanol tolerance, and superior durability. In order to understand the effects of different transition metal centers on the electrocatalytic performance of M-CNTFs, corresponding calculations were performed based on the density functional theory (DFT). Results reveal that the metal active sites and hydrophilic property of the metal-carbon system play an important role in enhancing the electrocatalytic ability, which is significant for further research on (or synthesis of) excellent catalytic materials for ORR.

Transition-metal phosphides (TMPs) have emerged as promising catalyst candidates for the hydrogen evolution reaction (HER). Although numerous methods have been investigated to obtain TMPs, most rely on traditional synthetic methods that produce materials that are inherently deficient with respect to electrical conductivity. An electrospinning-based reduction approach is presented, which generates nickel phosphide nanoparticles in N-doped porous carbon nanofibers (Ni2 P@NPCNFs) in situ. Ni2 P nanoparticles are protected from irreversible fusion and aggregation in subsequent high-temperature pyrolysis. The resistivity of Ni2 P@NPCNFs (5.34 Ω cm) is greatly decreased by 104 times compared to Ni2 P (>104 Ω cm) because N-doped carbon NFs are incorporated. As an electrocatalyst for HER, Ni2 P@NPCNFs reveal remarkable performance compared to other previously reported catalysts in acidic media. Additionally, it offers excellent catalytic ability and durability in both neutral and basic media. Encouraged by the excellent electrocatalytic performance of Ni2 P@NPCNFs, a series of pea-like Mx P@NPCNFs, including Fe2 P@NPCNFs, Co2 P@NPCNFs, and Cu3 P@NPCNFs, were synthesized by the same method. Detailed characterization suggests that the newly developed method could render combinations of ultrafine metal phosphides with porous carbon accessible; thereby, extending opportunities in electrocatalytic applications.

Hybrid ion capacitors, especially sodium ion capacitors (SICs), have recently attracted enormous attention due to their combined merits of high energy density from the battery-type anode and high power density from the capacitor-type cathode. However, achieving high-performance SICs to overcome the sluggish kinetic energy storage feature and inferior cycling stability of the battery-type anode remains a challenge. In this work, N-doped porous carbon embedded with ultrasmall titanium oxynitride nanoparticles (TiOxNy/C) was developed from metal–organic frameworks (MOFs). As the SIC anode, the as-designed TiOxNy/C exhibited a high reversible capacity (275 mA h g−1 at 50 mA g−1), ultrahigh rate capability, and superior cycling performance, which is attributed to the effective synergy between the ultrasmall TiOxNy nanoparticles and N-doped porous carbon. Furthermore, using a “two-for-one” strategy, N-doped hierarchical porous carbon (NHPC) with high surface area was prepared from TiOxNy/C by HF etching and displayed high specific capacity and rate capability when used as a SIC cathode. Considering the excellent electrochemical performances of both the anode and cathode, the as-assembled TiOxNy/C//NHPC SIC delivered a high energy density (80 W h kg−1) and high power density (4000 W kg−1).

Engineering the microstructure at the atomic scale is paramount to developing effective catalysts due to the active sites and mass/charge transfer ability of catalysts severely limited by their microstructure. Herein, we nanoengineer unique necklace-like nanochains composed of molybdenum nitride embedded N-doped carbon, in which the series-wound nanochains are built from hollow beads with a very thin porous wall. MoN nanodots were downsized to 3 nm and uniformly embedded in hollow N-doped porous carbon pearls and wires. The unique hierarchical hollow cavity and ultrathin wall structure of the nanochains offer a high effective reaction chamber, more active sites, and mass/charge transfer for remarkably fast HER. The resultant MoN@NPCNCs exhibit an extremely low HER overpotential of 72 mV at 10 mA cm−2, a low Tafel slope of 53.21 mV dec−1 in an acidic solution, which is far lower than those of MoN embedded N-doped carbon nanofibers (MoN@NPCNFs, 139.21 mV vs. RHE/82.69 mV dec−1), and other previously reported MoN based catalysts. Density functional theory (DFT) calculations reveal that MoN and N-doped carbon synergistically optimizes the free energy of hydrogen adsorption on the active sites. Furthermore, this catalyst also offers an excellent electrocatalytic ability and durability in both neutral and alkaline media.

Li-Te batteries have been attracted much attention as a potential research for energy storage systems due to the overwhelming features in superior electronic conductivity and ultrahigh theoretical volumetric capacity when compared to Li-S and Li-Se batteries. The main challenge to develop Li-Te battery systems is to explore an ideal substrate for Te accommodation. Here we have designed and exploited a “muscle” structured electrode, which enables an excellent electrochemical performance. Te is confined in the hollow carbon cell as “tissue cell” and carbon nanotubes (CNTs) are induced as “blood capillary”. Such an interesting design possesses multifold advantages. Specifically, many hollow carbon cells not only offer large void space for loading Te, giving rise to high mass loading of active materials, but also manifest a good contact between Te and carbon. In addition, the introduction of CNTs provides abundant channels along CNTs in the composites for both electron and ion transport upon cycling, yielding high discharge capacity. With this desired design, muscle-like electrode shows a high specific capacity of ~ 240 mA h g -1 after 500 cycles. This work would offer new ideas for developing other exceptional electrodes for energy storage applications.

Ammonia pollution poses serious threats to public health, especially in livestock. Developing an efficient method to eliminate ammonia is critical for environmental control in agricultural livestock. Herein we fabricate a one-dimensional coaxial nanobelts of molybdenum disulfide growth on titanium dioxide encapsulated carbon nanobelts (MoS2@TiO2 CNBs) by electrospinning followed hydrothermal reaction method. The as-prepared catalysts were used to photocatalytic degradation of ammonia gas, and the experiment results show that MoS2@TiO2 CNBs displayed excellent photocatalytic activity and degraded ammonia gas with 91% efficiency after only 7 min, which mainly attributed to the synergistic effect from chemical compositions and the robust banding structure. Additionally, we propose an economical, convenient, and effective in situ analysis and monitoring method for photodegradation of ammonia, which presents promising application for further development of other high efficient photocatalysts for toxic pollutant degradation.

Elaborate design of efficient and stable electrocatalysts from earth-abundant elements to replace precious Pt for the hydrogen evolution reaction (HER) is an ongoing challenge. Doping metallic compounds with additional metal atoms provides the opportunity to tune their electronic and crystal structures, thus ameliorating their electrocatalytic properties. Here, we report for the first time a robust and earth-abundant Ni-doped Co3S4 catalyst grown on carbon cloth that showed high HER activity in 1 M KOH. The morphology evolution and HER activity are strongly related to the Ni substitution ratio. Electrochemical tests showed a low overpotential of 72.82 mV at 10 mA*cm-2, small Tafel slope of 49.44 mV*dec-1, and long-term durability over 46 h HER operation for the Ni0.5Co2.5S4 nanotube array self-standing on carbon cloth. These data indicate that atomic modulation of Ni plays an important role in optimizing the morphology and electrocatalytic activity by greatly expanding the active sites in the electrocatalyst. Further, the 3D self-standing nanotube array highly aids the exposure of active species and transfer of electrons and charges, substantially boosting the reaction kinetics and structure stability.

For the future of fuel cells, investigations on high activity, stable, and low-cost oxygen-reduction reaction (ORR) catalysts are critical. Transition metals have attracted particular research interest in pursuit of such efficient and sustainable ORR electrocatalysts. In this work, very tiny Co nanoparticles were assembled on 3D graphene (3DG) aerogels uniformly with the help of ascorbic acid (AA) under a facile hydrothermal process. After further thermal annealing in argon, a few carbon layers are formed and wrapped on the Co nanoparticles. The synthesized materials were primarily investigated for ORR, and the experimental results indicate that the as-prepared Co/3DG shows an obviously positive onset potential (−0.01 V) and a much higher limiting current density (5.75 mA/cm2) than Co/3DG prepared without using AA (−0.1 V, 4.6 mA/cm2). Compared with commercial 20%Pt/C, Co/3DG prepared by using AA also displayed excellent durability and superb methanol tolerance performance, which suggests that the special structure of cobalt nanoparticles wrapped with a few carbon layers and its porous 3DG aerogel support can prevent its expansion and dissolution, improve its stability largely, and provide a new way for searching excellent ORR electrocatalysts.

An oxygen reduction reaction (ORR) electrocatalyst with high performance, low cost and good durability is extremely desirable for promoting the commercial application of fuel cells. Much efforts have been made to explore efficient and nonprecious catalysts to replace the platinum-based catalyst. Particularly, cobalt oxide (Co3O4 or CoO) decorated carbon materials has been demonstrated as promising ORR electrocatalysts. In this paper, we report a kind of tiny hollow nano-Co3O4 anchored 3D graphene aerogels (3DG) in the first time, which derived from direct oxidation carbon wrapped Co/3DG through Kirkendall effect. Due to its unique structure, the hollow Co3O4/3DG shows excellent ORR catalytic activity with almost four-electron reduction pathway, high methanol tolerance and long-term durability in alkaline media.

Lithium-sulfur (Li-S) batteries are of great importance as promising electrochemical-energy storage systems in view of their overwhelming advantage of energy density. However, their commercial applications are still far away mainly due to fast capacity decay in a high sulfur content caused by low utilization of active material and severe polysulfide dissolution during electrochemical cycling. Here we have designed and prepared uniform α-Ni(OH)2 hollow spheres constructed from ultrathin nanosheets with the thickness of ~3.5 nm as a hollow sulfur nanosphere host for Li-S batteries. Specifically, the synthesized hierarchical hollow spheres not only manifest the advantages of hollow structure and robust protective shell to encapsulate a very high content of sulfur up to 81 wt%, but also offer sufficient functionalized surfaces to directly bond and entrap polysulfides in hollow sphere. When used as cathode materials for Li-S batteries, the S@Ni(OH)2 double-shell hollow hybrids exhibit a highly stable cycle life over 1000 cycles at 1 C with a very small capacity decay rate of only ~0.04% per cycle.

The authors have synthesized nanostructured manganese(II) phosphate hollow spheres [Mn3(PO4)2 HS] with tunable pore structure by using a micro-emulsion method. These, if deposited on a glassy carbon electrode (GCE), are shown to be a viable material for electrochemical sensing of superoxide (radical) anion (O2˙−) at a typical working voltage of 0.7 V (vs. SCE). Hence, they act as biomimetic enzymes that allow for the determination of O2˙− with a very low detection limit (1.35 nM), wide linear range (5 nM to 0.4 mM), and good long-term stability. The modified GCE was applied in-situ to the electrochemical determination of O2 − that is released from human malignant melanoma cells and normal keratinocyte, and it showed excellent real time analytical capability. In our perception, the use of this material offers exciting opportunities in terms of implementing nanoscale transition metal phosphates as biomimetic enzymes in enzyme-free diagnostic sensors. Conceivably, these will offer higher sensitivity and longer durability than assays based on the use of natural enzymes.

Here, we develop a novel method to successfully prepare a nanohybrid catalyst of carbon framework wrapped cobalt phosphide on carbon cloth (Co2P@C/CC) as a flexible electrocatalyst for the HER. Relative to reported phosphides phosphatized using hypophosphite, the resulting Co2P@C/CC was prepared using a Co3(PO4)2 precursor via one-step chemical vapor deposition (CVD) reduction, thus obtaining highly purified Co2P. This moderate method paves a versatile path to designing earth-abundant alternatives for the HER.

Monitoring superoxide anion radicals in living cells has been attracting much academic and industrial interest due to the dual roles of the radicals. Herein, we synthesized a novel nanostructured cobalt phosphate nanorods (Co3(PO4)2 NRs) with tunable pore structure using a simple and effective micro-emulsion method and explored their potential utilization in the electrochemical sensing of superoxide anions. As an analytical and sensing platform, the nanoscale biomimetic enzymes Co3(PO4)2 NRs exhibited excellent selectivity and sensitivity towards superoxide anion (O2•-) with a low detection limit (2.25nM), wide linear range (5.76-5396nM), and long-term stability. Further, the nanoscale biomimetic enzyme could be efficiently applied in situ to electrochemically detect O2•- released from human malignant melanoma cells and normal keratinocyte, showing excellent real time quantitative detection capability. This material open up exciting opportunities for implementing biomimetic enzymes in nanoscale transition metal phosphates and designing enzyme-free biosensors with much higher sensitivity and durability in health and disease analysis than those of natural one.

Novel K3V2(PO4)3 and three-dimensional conductive network K3V2(PO4)3/C nanocomposites are successfully fabricated and further evaluated as cathode materials for potassium-ion batteries for the first time. The K3V2(PO4)3/C nanocomposite exhibits a high-potential platform of 3.6–3.9 V and a good capacity retention of at least 100 cycles. This work may provide new insight into developing cathode materials for potassium-ion batteries.

The rational construction of low cost, efficient, and stable oxygen reduction reaction (ORR) electrocatalysts is important for the commercialization of fuel cells and metal–air batteries. In this article, we report an easy and effective soft-template method to in situ assemble Fe2N nanoparticles on the surface of N-doped graphene-like carbon (NC). The prepared Fe2N nanoparticles were covered by a few carbon layers, which promoted the connection of Fe–NX clusters with graphene to facilitate the formation of Fe–N–C active sites. Fe–NX and NC units were found to respectively fulfill different functionalities, and commonly afford the sample with excellent performance. The electrochemical data show that the Fe2N@NC composite with high-purity and good crystalline displays a synergistic enhanced catalytic activity for ORR, including a positive onset potential (0.084 V), a half-wave potential (−0.036 V) and a high electron transfer number (∼4e−), as compared to 20% Pt/C. Additionally, the existence of carbon shells wrapped around Fe2N nanoparticles can restrain their expansion and dissolution. In addition, the as-prepared catalyst was implemented as an air catalyst for zinc–air batteries and was found to display a comparable open circuit voltage of ca. 1.48 V and a maximum power density of 82.3 mW cm−2. These results demonstrate that the Fe2N@NC catalyst may serve as a good alternative to precious Pt for ORR in practical applications.

In this work, ultrathin graphene-like carbon nitride nanosheets with rich nanoporous and excellent hydrophilic characteristics were synthesized by a simple and effective thermal exfoliation of bulk g-C3N4. In order to fully understand the effect of thermal exfoliation conditions on the texture, surface state, and photocatalytic activity of the resulting g-C3N4, a series of exfoliated g-C3N4 were prepared by adjusting the thermal exfoliation temperature and time. The detailed characterization and analysis distinctly suggested that increasing exfoliation temperature led to a large number of nitrogen vacancies and increased specific surface area, further prolonging exfoliation time, the thermal exfoliation degree was enhanced, more carbon vacancies and enlarged pore volume formed in the resulting products. Further, the exfoliation degree and photocatalytic ability of the resultant products were enhanced by increasing thermal exfoliation temperature and time. The optimized ultrathin graphene-like carbon nitride nanosheets exhibited a 89.6% degradation efficiency for Rh6G only in 10 min, which was much faster than other such nanosheets reported in previous literature.

A corn-like CeO2/C coaxial cable textured by a cerium oxide shell and a carbon core was designed to sense NO. The carbon core possesses high electrical conductivity, and the CeO2 surface delivers excellent electrocatalytic activity. The sensor, typically operated at 0.8 V (vs. Ag/AgCl), exhibits a detection limit of 1.7 nM, which is 4-times lower than that of CeO2 nanotubes based one (at S/N = 3). It also displays wide linear response (up to 83 μM), a sensitivity of 0.81 μA μM−1 cm−2, and fast response (2 s). These values are highly competitive to that of a CeO2 tube (0.92 μA μM−1 cm−2 and 2 s). The sensor was used to quantify NO that is released by Aspergillus flavus.

During the development of oxygen reduction reaction electrocatalysts, transition-metal nanoparticles embedded in N-doped graphene have attracted increasing attention owing to their low-priced, minimal environmental impact, and satisfying performance. In this study, a new organic-cadmium (Cd) complex formed through Cd2+ coordination with p-phenylenediamine (PPD) was used to synthesize highly active Fe-embedded N-doped carbon catalysts for the first time. It is significant that with the decreasing molar ratio of Cd/Fe, an obvious microstructure evolution was observed in Cd-Fe-PPD from diamond-like blocks to thick flakes, and further bloomed into flowerlike shapes with ultrathin petals and then eventually exhibited large block starfish-like shapes. After carbonization, Cd was removed, slack and porous N-doped carbon was formed, and Fe was assembled in the N-doped carbon. Similar phenomenon was also observed in Co-PPD. The optimized Fe/NPC-2 material featuring uniform and well-dispersed 3-5 nm Fe nanoparticles embedded in two-dimensional ultrathin carbon nanosheets delivered excellent electrocatalytic performance ( Eonset: 0.96 V vs reversible hydrogen electrode (RHE), E1/2: 0.84 V vs RHE), which is very close to those of commercial platinum on carbon (Pt/C) ( Eonset: 0.95 V vs RHE, E1/2: 0.84 V vs RHE), and its methanol tolerance and durability also surpass those of Pt/C.

Two-dimensional bismuth oxychloride (BiOCl) ultrathin nanoplates with a thickness of 10–20 nm are synthesized by a simple hydrothermal method. The as-prepared product is explored as an anode material for sodium-ion batteries for the first time. It shows BiOCl ultrathin nanoplates with two very suitable discharge voltage plateaus (0.6 V and 0.4 V) for sodium ion batteries. Furthermore, a two-step sodiation mechanism including an intercalation reaction and a conversion reaction is proposed. This work reveals a novel electrode material for sodium-ion batteries beyond conventional materials (such as transition metal oxides, carbon materials and alloys) and encourages more researchers to further investigate BiOCl.

A low-cost, high-performance, and durable catalyst for oxygen reduction reaction (ORR) is prerequisite for the commercialization of fuel cells. Continuous efforts are made to explore nonprecious, efficient catalysts to replace the expensive and scare platinum-based catalysts. Here, we demonstrate a kind of novel nitrogen and phosphorus co-doped mesoporous carbon spheres (NPMCS) synthesized by hydrothermal assisting pyrolysis of food yeast. The as-prepared mesoporous carbon hollow spheres exhibit a high specific surface area of 1223 m2 g−1, deliver an excellent electrocatalytic performance for ORR in alkaline media, superior durability and high resistance to methanol cross-over effect.

A glassy carbon electrode (GCE) was modified with a nanocomposite consisting of tetraoctylammonium bromide (TOAB), C60 fullerene, and palladium nanorods (PdNRs). The PdNRs were hydrothermally prepared and had a typical width of 20 ± 2 nm. The nanocomposite forms stable films on the GCE and exhibits a reversible redox pair for the C60/C60 − system while rendering the surface to be positively charged. The modified GCE was applied to fabricate an electrochemical biosensor for detecting acetylcholinesterase (AChE) by measurement of the amount of thiocholine formed from acetylthiocholine, best at a working voltage of −0.19 V (vs. SCE). The detection scheme is based on (a) measurement of the activity of ethyl paraoxon-inhibited AChE, and (b) measurement of AChE activity after reactivation with pralidoxime (2-PAM). Compared to the conventional methods using acetylthiocholine as a substrate, the dual method presented here provides data on the AChE activity after inhibition and subsequent reactivation, thereby yielding credible data on reactivated enzyme activity. The linear analytical range for AChE activity extends from 2.5 U L−1 to 250 kU·L−1, and the detection limit is 0.83 U L−1.

We report a general approach for the synthesis of yolk–shell-structured porous dicobalt phosphide/zinc oxide@porous carbon polyhedral/carbon nanotube hybrids (Co2P/ZnO@PC/CNTs) derived from bimetal–organic frameworks, and explore their potential utilization in the electrochemical sensing of superoxide anions. Beyond our expectation, the trace level of O2˙− released from living cells has also been successfully captured by our designed sensor. The presented strategy for the controlled design and synthesis of bimetal–organic frameworks-derived functional nanomaterials offers prospects of developing highly active electrocatalysts in non-enzyme sensors.

Large-scale electrochemical water splitting is hindered by the sluggish oxygen evolution reaction (OER) kinetics. In this work, we report a vertically standing Fe3O4-FeSe/CoSe2 hierarchical structure material grown on carbon cloth as a highly active OER electrocatalyst. Benefiting from the rock-like Fe3O4 particles on the carbon cloth, the CoSe2 nano-arrays are more firmly affixed onto the carbon cloth. In addition, small amount of FeSe particles adsorbed on the CoSe2 arrays offer a synergistic advantage, in which CoSe2 achieved a small 279 mV overpotential at a current density of 10 mA cm−2 and a low Tafel slope of 68.78 mV dec−1. By comparing the performance of Fe3O4-FeSe/CoSe2 with pure CoSe2 and Fe3O4-FeSe, it demonstrates to be the most efficient OER catalyst. Significantly, the hierarchical structural strategy of fixed Fe3O4 growth on carbon cloth arrays introduces a new concept to explore the design of high efficiency OER electrocatalysts.

A novel book-like K0.23V2O5 crystal is obtained by a simple hydrothermal method and is explored as a cathode material for Li-ion batteries for the first time. It exhibits a high reversible capacity (of ca. 244 mA h g(-1) at a current density of 50 mA g(-1)), along with a good rate capability (80 mA h g(-1) at a current density of 1800 mA g(-1)) and a good capacity retention (185.3 mA h g(-1) after 100 cycles).

Novel K2Ti8O17 is successfully fabricated via a facile hydrothermal method combined with a subsequent annealing treatment and further evaluated as an anode material for potassium-ion batteries for the first time. This study may provide a broader vision into developing anode materials for potassium-ion batteries.

Metal-organic framework (MOF)-derived hollow cobalt sulfides have attracted extensive attention due to their porous shell that provides rich redox reactions for energy storage. However, their ultradispersed structure and the large size of MOF precursors result in relatively low conductivity, stability, and tap density. Therefore, the construction of an array of continuous hollow cages and tailoring of the inner cavity of MOF-derived materials is very effective for enhancing the electrochemical performance. Herein, we in situ assembled small Co-based zeolitic imidazolate framework (ZIF-67) on the both sides of negatively charged MnO2 nanosheets to fabricate a hierarchical sandwich-type composite with hollow cobalt sulfide nanocages/graphene-like MnO2. The graphene-like MnO2 nanosheets acted not only as a structure-directing agent to grow a ZIF-67 array but also as a promising electroactive material of electrochemical capacitors to provide capacitance. As an electrode material of supercapacitors, the as-pre...

Polycrystalline K2Ti8O17 is prepared by hydrothermal reaction of (BuO)4Ti and KOH in a 1:1 mixture of ethylene glycol and H2O (autoclave, 200 °C, 20 h) followed by calcination in air (700 °C, 12 h).

In this communication, a novel platanus hispanica-like, highly integrated hierarchical electrocatalyst, with Co–carbon nanotubes anchored through porous Co embedded carbon sphere frameworks (Co–CNTFs), was fabricated using a chemical vapor deposition (CVD) method. More importantly, the prepared Co–CNTFs demonstrate even better activity than commercial Pt electrocatalysts in an alkaline medium. This presented CVD approach provides an effective way to grow metal–CNTs in situ through various metal-complex-derived functional nanomaterials and can be expanded to metallic oxide, metallic sulfide, and metallic phosphide, among others, to introduce carbon nanotube frameworks with a multitude of potential applications.

In this communication, we designed and synthesized a novel calcium-organic framework and presented it as an anode material for sodium-ion batteries. The results show that it delivers a reversible capacity of higher than 140 mA h g(-1) even after 300 cycles. The remarkable performance is attributed to the high structural stability and extremely low solubility of the calcium-organic framework in electrolytes.

A novel book-like K0.23V2O5 crystal is obtained by a simple hydrothermal method and is explored as a cathode material for Li-ion batteries for the first time. It exhibits a high reversible capacity (of ca. 244 mA h g−1 at a current density of 50 mA g−1), along with a good rate capability (80 mA h g−1 at a current density of 1800 mA g−1) and a good capacity retention (185.3 mA h g−1 after 100 cycles).