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CoMoO4 nanoparticles have been successfully in-situ formed and simultaneously embedded within the porous carbon nanofibers (CoMoO4/CNFs) via a facile electrospinning-annealing strategy. The porous CoMoO4/CNFs exhibit a specific surface area of 255.3 m2/g and a pore volume of 0.52 cc/g with average pore diameter of 43.5 nm. The carbon content in the CoMoO4/CNFs can be readily controlled by adjusting the annealing temperature. When examined as anode materials for lithium ion batteries (LIBs), the CoMoO4/CNFs demonstrate superior electrochemical performance, delivering a high reversible capacity of 802 mA h/g after 200 cycles at 200 mA/g and a high-rate capacity of 574 mA h/g at 2000 mA/g. The excellent lithium storage behavior can be attributed to the incorporation of CoMoO4 nanoparticles into the porous N-doped graphitic carbon nanofibers, which efficiently buffer the volume changes of CoMoO4 upon lithiation/delithiation and maintain the overall electrode conductivity/integrity.

Preparing high-efficiency electrocatalyst through facile, low energy consumptive, and time-effective strategy is essential to the hydrogen generation via water electrolysis. Here, we report a galvanic replacement-mediated synthesis of highly active Co–Fe layered double hydroxides (Co–Fe LDHs) at room temperature as advanced electrocatalyst for water oxidation. The disc-like Co precursors were the first proposed as self-sacrificing templates for Co–Fe LDHs. By steady control of the carving of iron ions, the disc-like Co precursors are carved relaxedly and then formed to nanosheet-constructed Co–Fe LDHs. The Fe (II) ion is proved to a more preferable iron precursor than Fe (III) ion for Co–Fe LDHs nanosheets growth, owing to the “slow-growth” process. This catalyst shows a highly electrocatalytic activity towards the OER with low overpotential (η10 mA cm -2 = 270 mV), low Tafel slope (48.7 mV dec-1), and remarkable long-time stability.

We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO2/MoO3 into porous foam-like carbon nanoflakes (denote as SnO2/MoO3@CNFs, or SMC in short), which are simply prepared by annealing tin(II)/molybdenum(IV) 2-ethylhexanoate within CNFs under ambient atmosphere at a low temperature (300 °C). The SnO2/MoO3 loading amount within CNFs can be easily adjusted by controlling the Sn/Mo/C precursors. When examined as lithium ion battery (LIB) anode materials, the amorphorized SnO2/MoO3@CNFs with carbon content of 32 wt% (also denote as SMC-32, in which the number represents the carbon content) deliver a high reversible capacity of 1120.5 mA h/g after 200 cycles at 200 mA/g and then 651.5 mA h/g after another 300 cycles at 2000 mA/g, which is much better than that of the crystalline SnO2/CNFs (carbon content of 34 wt%), MoO3/CNFs (carbon content of 22.7 wt%), or SnO2/MoO3@CNFs (with lower carbon contents of 11 and 25 wt%). The electrochemical measurements as well as the ex situ structure characterization clearly suggest that combination of amorphorization and hybridization of SnO2/MoO3 with CNFs synergistically contributes to the superior lithium storage performance with high pseudocapacitive contribution.

Photocatalytic hydrogen evolution from water splitting driven by visible light is a promising approach to solve energy crisis and environmental problems, and noble-metal-free co-catalysts for boosting the hydrogen evolution reaction are highly desired. Herein, we explore a novel noble-metal-free Fe2P–Co2P co-catalyst for the first time to boost the photocatalytic performance of graphitic carbon nitride (g-C3N4). The resultant Fe2P–Co2P/g-C3N4 with optimum ratio exhibits a hydrogen production rate of 347 μmol h−1 g−1 in the absence of noble-metal co-catalyst, which is 87 times higher than that of pristine g-C3N4 under the same conditions. The significant enhancement in the photocatalytic performance of Fe2P–Co2P/g-C3N4 can be ascribed to the Schottky junction formed between Fe2P–Co2P and g-C3N4, which produces a strong driving force for the transfer of electrons from g-C3N4 to Fe2P–Co2P, promoting the separation and transfer of photogenerated electrons and holes. Furthermore, due to the synergistic effects between the two metal phosphides (Fe2P and Co2P), the Schottky junction in Fe2P–Co2P/g-C3N4 can produce stronger driving force than that in Fe2P/g-C3N4 and Co2P/g-C3N4, resulting in the fact that the hydrogen production rate over Fe2P–Co2P/g-C3N4 is much higher than that over Fe2P/g-C3N4 and Co2P/g-C3N4. This work may shed light on the careful design of co-catalyst by utilizing the synergistic effect of different components.

Transition metal oxides (TMOs) have been regarded as promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacities, natural abundance, and eco-friendliness. However, their large volume changes and the thus resulting pulverization problem, as well as the poor electrical conductivity, have hindered their practical applications. Design of hollow nanostructures with simultaneous carbon hybridization has shown great promise to overcome these drawbacks. Herein, we demonstrate a facile strategy to fabricate hollow Co3O4 nanoparticle-assembled nanofibers with controllable carbon content via electrospinning and subsequent annealing. Interestingly, the solid Co nanoparticles encapsulated within carbon nanofibers convert into hollow Co3O4 counterparts under ambient oxidation in air, and the carbon content can be easily adjusted by controlling the annealing temperature/time. When used as anode materials for LIBs, the hollow Co3O4 nanoparticle-assembled nanofibers (no carbon left) deliver a high discharge capacity of 1491.5 mA h g−1 after 180 cycles at 200 mA g−1, demonstrating superior lithium storage properties. Notably, optimized Co3O4/C nanofibers with 10 wt% carbon content demonstrate superior cycling stability, delivering a stable reversible capacity of ∼871.5 mA h g−1 after 500 cycles at 200 mA g−1. The superior electrochemical performance of the Co3O4(/C) nanofibers could be ascribed to the unique hollow nanostructure of Co3O4, the carbon hybridization, and the novel hierarchical nanoparticle-nanofiber assembly, which could not only shorten the lithium diffusion length, but also efficiently buffer the volumetric changes upon repeated lithiation/delithiation processes.

MoO3 as electrode material for lithium ion batteries (LIBs) suffers from the poor ionic and electronic conductivity, while hybridizing nanostructured MoO3 with carbon-based materials is regarded as an efficient strategy. Herein, we report the facile synthesis of MoO3 nanoplates within foam-like carbon nanoflakes (CNFs) via the pyrolysis of molybdenum 2-ethtlhexanoate (C48H90MoO12) at a low temperature of 300 °C under ambient atmosphere. Mixing C48H90MoO12 with the highly porous foam-like CNFs allows the sufficient pyrolysis of Mo precursor, which can readily crystallize into MoO3 with plate morphology. The loading amount of MoO3 within CNFs can be easily and precisely controlled by adjusting the relative amount of C48H90MoO12/CNFs, while the plate morphology of MoO3 can be well preserved. The structural characteristics as well as the formation mechanism are investigated. When used as anode material for LIBs, optimized MoO3/CNFs displays superior lithium storage performance, delivering a high discharge capacity of 791 mA h/g after 100 cycles at 500 mA/g and even ∼600 mA h/g at a high rate of 2000 mA/g. Moreover, the present pyrolysis synthetic strategy can be generally applied for low-cost and large-scale fabrication of various MoO3/carbon nanocomposites, which demonstrates great potential in the development of high-performance electrodes for electrochemical energy-storage.

Atomic layer deposition (ALD) of TiO2 shells on MoO3 nanobelts (denote as TiO2@MoO3) is realized using a home-made ALD system, which allows a controllable hydrolysis reaction of TiCl4–H2O on an atomic scale. When used as an anode material for lithium ion batteries, the TiO2@MoO3 electrode demonstrates much enhanced lithium storage performance including higher specific capacity, better cycling stability and rate capability.

To address the volume change-induced pulverization problem of tin-based anodes, a concept using hollow carbon nanoballs (HCNBs) as buffering supports is herein proposed. HCNBs with hollow interior, flexibility and graphitic crystallization are first prepared by a combined method of chemical vapor deposition (CVD) and template-synthesis using CH4 as the carbon source and CaCO3 as the conformal template. The ultrafine SnO2 nanoparticles are loaded onto the HCNBs (denoted as SnO2@HCNBs) via pyrolysis of tin(II) 2-ethylhexanoate at 300 °C in air. On further annealing SnO2@HCNBs in Ar, SnO2 is partially reduced to SnOx by consuming a part of carbon of HCNBs as the reducing agent, and thus SnOx@HCNBs are obtained (note that SnOx represents a composite consisting of SnO2, SnO and Sn phases). When applied as anode materials for lithium ion batteries (LIBs), HCNBs deliver high reversible capacities of 841 mA h g−1 after 125 cycles at 200 mA g−1, and 726 mA h g−1 after 400 cycles even at 1000 mA g−1, while SnO2@HCNBs and SnOx@HCNBs exhibit discharge capacities of 1042 and 1299 mA h g−1 after 400 cycles at 200 mA g−1, respectively. Notably, all of them display gradually increased capacity with retention over 100% even after long-term cycling, which is attributed to the novel robust characteristic of the HCNBs as revealed by the ex situ TEM analysis. The flexible hollow HCNBs with high graphitic crystallization not only efficiently tolerate the volume changes of the Li–Sn alloying–dealloying but also facilitate the electrolyte/charge transfer owing to the hollow structure and high conductivity of the HCNBs.

CoMoO

We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO

We demonstrate a facile hydrothermal synthesis of SnO 2 /MoO 3-x nanocomposites with ultrafine SnO 2 crystallites uniformly embedded into an amorphous MoO 3-x matrix, which demonstrate superior electrochemical performance as anodes for lithium ion batteries, including long-term cycling stability (953 mA h/g after 100 cycles at 200 mA/g), high rate capability (668.0 mA h/g after 1000 cycles at 1000 mA/g) and high initial Coulombic efficiency (81.3% at 200 mA/g). Synergistic effects of the both components SnO 2 and MoO 3-x on the lithium storage are revealed by electrochemical characterization and supported by TEM and XPS analysis performed at the different discharge/charge states of the respective electrodes. SnO 2 nanocrystallites confined within the amorphous MoO 3-x matrix efficiently buffer the volume changes of Li-Sn alloying-dealloying upon cycling, while the metallic Mo in situ generated by a conversion reaction of MoO 3-x promotes the reversible reaction SnO 2 + Li + ↔ Sn + Li 2 O. In addition, the amorphous MoO 3-x with bulk or surface defects allows for a better lithium insertion and thus enhanced capacity.

Multidimensional architecture design is a promising strategy to explore unique physicochemical characteristics by synergistically integrating different structural and compositional materials. Herein, we report the facile synthesis of a novel dendritic hybrid architecture, where carbon nanotubes (CNTs) with nickel sulfide nanoparticles encapsulated inside are epitaxially grown out of the porous electrospun N-doped carbon nanofibers (CNFs) (denoted as CNT@NS@CNFs) through a combined strategy of electrospinning and chemical vapor deposition (CVD). The adopted thiophene (C4H4S) not only serves as a carbon source for the growth of CNTs but also as a sulfur source for the sulfurization of Ni particles and S-doping into carbon matrices. When examined as an anode material for lithium-ion batteries (LIBs), the dendritic CNT@NS@CNFs display superior lithium storage properties including good cycle stability and high rate capability, delivering a high reversible capacity of 630 mA h g−1 at 100 mA g−1 after 200 cycles and 277 mA h g−1 at a high rate of 1000 mA g−1. These outstanding electrochemical properties can be attributed to the novel hybrid architecture, in which the encapsulation of nickel sulfide nanoparticles within the CNT/CNFs not only efficiently buffers the volume changes upon lithiation/delithiation, but also facilitates charge transfer and electrolyte diffusion owing to the highly conductive networks with open frame structures.

In order to suppress the shuttling of soluble lithium polysulfides in Li-S batteries and increase the conductivity of the sulfur cathode, here we report the design and synthesis of three-dimensional (3D) highly ordered porous carbon bulk network (PCBNs), using silica (SiO2) nanospheres as removable hard templates and soluble starch as carbon source. After carbonization and template removal, the as-prepared PCBNs composed of interconnected hollow carbon balls exhibit large surface area (447.4 m2/g) and large pore volume (1.567 cm3/g), high graphitization degree and robust framework. Serving as an efficient sulfur host, PCBNs supported sulfur cathode (S@PCBNs with sulfur content of 72 wt%) delivers a high discharge capacity of 760 mA h/g after 150 cycles at 0.1 C and 455 mA h/g after 400 cycles at 1 C. The superior lithium storage properties is attributed to the novel hierarchical microstructure of the PCBNs, in which the large hollow space not only allows high loading of sulfur but also efficiently accommodates the large volumetric expansion. Moreover, the interconnected PCBNs with high conductivity can spatially confine the shuttling of soluble polysulfides and enhance the redox reaction kinetics.

Atomic layer deposition (ALD) of TiO2 shells on MoO3 nanobelts (denote as TiO2@MoO3) is realized using a home-made ALD system, which allows a controllable hydrolysis reaction of TiCl4-H2O on an atomic scale. When used as an anode material for lithium ion batteries, the TiO2@MoO3 electrode demonstrates much enhanced lithium storage performance including higher specific capacity, better cycling stability and rate capability.

To address the volume change-induced pulverization problem of tin-based anodes, a concept using hollow carbon nanoballs (HCNBs) as buffering supports is herein proposed. HCNBs with hollow interior, flexibility and graphitic crystallization are first prepared by a combined method of chemical vapor deposition (CVD) and template-synthesis using CH4 as the carbon source and CaCO3 as the conformal template. The ultrafine SnO2 nanoparticles are loaded onto the HCNBs (denoted as SnO2@HCNBs) via pyrolysis of tin(ii) 2-ethylhexanoate at 300 °C in air. On further annealing SnO2@HCNBs in Ar, SnO2 is partially reduced to SnOx by consuming a part of carbon of HCNBs as the reducing agent, and thus SnOx@HCNBs are obtained (note that SnOx represents a composite consisting of SnO2, SnO and Sn phases). When applied as anode materials for lithium ion batteries (LIBs), HCNBs deliver high reversible capacities of 841 mA h g-1 after 125 cycles at 200 mA g-1, and 726 mA h g-1 after 400 cycles even at 1000 mA g-1, while SnO2@HCNBs and SnOx@HCNBs exhibit discharge capacities of 1042 and 1299 mA h g-1 after 400 cycles at 200 mA g-1, respectively. Notably, all of them display gradually increased capacity with retention over 100% even after long-term cycling, which is attributed to the novel robust characteristic of the HCNBs as revealed by the ex situ TEM analysis. The flexible hollow HCNBs with high graphitic crystallization not only efficiently tolerate the volume changes of the Li-Sn alloying-dealloying but also facilitate the electrolyte/charge transfer owing to the hollow structure and high conductivity of the HCNBs.

MoO

Transition metal oxides have attracted extensive attention as promising anodes for lithium ion batteries (LIBs) owing to their low cost and high theoretical capacities. However, the large volume changes upon lithiation/delithiation cycling gradually causes the drastic particle pulverization in the electrodes, thus leading to the fast capacity fading and limiting their practical applications. Ternary metal oxides with enhanced electronic conductivity and multiple electrochemically active sites display stepwise lithium storage behaviors, thus efficiently alleviating the volume change induced electrode pulverization problem. Herein, we report the synthesis of hierarchical CoMoO4 microspheres assembled from nanosheets via a facile hydrothermal method and subsequently annealing. When used as anodes for LIBs, the CoMoO4 electrode exhibits superior lithium storage properties, delivering large reversible capacities of 1008 and 896 mA h/g at current densities of 200 and 500 mA/g after 50 cycles, respectively, and notably an exceptional rate capacity of 444 mA h/g at 2000 mA/g. Design of ternary metal oxides with different electrochemically active components and novel nanostructures might be an useful strategy for exploring high-performance LIB anode materials in the next-generation energy storage devices.

In order to overcome the poor electrical conductivity of titania (TiO2) and silica (SiO2) anode materials for lithium ion batteries (LIBs), we herein report a facile preparation of integrated titania&ndash, silica&ndash, carbon (TSC) nanofibers via electrospinning and subsequent heat-treatment. Both titania and silica are successfully embedded into the conductive N-doped carbon nanofibers, and they synergistically reinforce the overall strength of the TSC nanofibers after annealing (Note that titania&ndash, carbon or silica&ndash, carbon nanofibers cannot be obtained under the same condition). When applied as an anode for LIBs, the TSC nanofiber electrode shows superior cycle stability (502 mAh/g at 100 mA/g after 300 cycles) and high rate capability (572, 518, 421, 334, and 232 mAh/g each after 10 cycles at 100, 200, 500, 1000 and 2000 mA/g, respectively). Our results demonstrate that integration of titania/silica into N-doped carbon nanofibers greatly enhances the electrode conductivity and the overall structural stability of the TSC nanofibers upon repeated lithiation/delithiation cycling.

We demonstrate a facile synthesis of ultrafine SnO2 nanoparticles within graphene nanosheets (GNSs) via thermal decomposition of tin-octoate, in which tin-octoate is firstly blended with GNSs followed by annealing in air at a low temperature (350 °C) and a short time (1 h). As anode for lithium ion batteries, the SnO2/GNSs displays superior cycle and rate performance, delivering reversible capacities of 803 and 682 mA h/g at current densities of 200 and 500 mA/g after 120 cycles, respectively, much higher than that of pure SnO2 and GNSs counterparts (143 and 310 mA h/g at 500 mA/g after 120 cycles, respectively). The enhanced electrochemical performance is attributed to the ultrafine SnO2 nanoparticle size and introduction of GNSs. GNSs prevent the aggregation of the ultrafine SnO2 nanoparticles, which alleviate the stress and also provide more electrochemically active sites for lithium insertion and extraction. Moreover, GNSs with large specific surface area (~363 m2/g) act as a good electrical conductor which greatly improves the electrode conductivity and also an excellent buffer matrix to tolerate the severe volume changes originated from the Li-Sn alloying-dealloying. This work provides a straight-forward synthetic approach for the design of novel composite anode materials with superior electrochemical performance.