Search

Efficient, rechargeable Mg and Ca batteries Divalent rechargeable metal batteries such as those based on magnesium and calcium are of interest because of the abundance of these elements and their lower tendency to form dendrites, but practical demonstrations are lacking. Hou et al . used methoxyethyl amine chelants in which the ligands attach to the metal atom in more than one place, modulating the solvation structure of the metal ions to enable a facile charge-transfer reaction (see the Perspective by Zuo and Yin). In full battery cells, these components lead to high efficiency and energy density. Theoretical calculations were used to understand the solvation structures. —MSL

Li10GeP2S12 (LGPS) has a high ionic conductivity and compatibility with sulfur cathodes; however, the instability of LGPS against Li and Li dendrite growth still remains unsolved. Here, we solved t...

Carbon materials with excellent light-harvesting capacity are promising light absorbers for solar-thermal conversion. However, developing advanced carbon materials with tailored morphology and properties that are suitable for solar steam generation remains challenging. Herein, we have successfully synthesized oxygen-enriched tubular carbon with uniform hollow architecture and some defective structure by pyrolysis of a coordination complex (PEG-CaCl2 precursor). Briefly, PEG molecules can promote the anisotropic growth of CaCl2 nanorods during pyrolysis through coordination interaction (Ca–O), and simultaneously serve as the carbon and oxygen sources for in-situ growth of self-doped tubular carbon using the as-formed nanorods as ideal templates. The resulting tubular carbon with one-dimensional hollow structure, possesses a large specific surface area (613 m2 g−1) for light absorption, low thermal conductivity (0.0474 W m−1 K−1) for heat localization, and abundant hydrophilic oxygen-containing groups (8.62 at.% oxygen) for efficient water delivery. Thus, the self-floating photothermal membrane based on the tubular carbon, fabricated by the addition of agar binder, exhibits broadband light absorption (96%) and achieves a high evaporation efficiency of 91.3% under one sun illumination. This work provides a new insight to design and synthesize functionalized carbon with controlled morphology and the desired structure for potential application in solar steam generation.

Multi-walled carbon nanotubes-titanium dioxide (MWCNTs-TiO2) nanocomposites were synthesized via microwave-assisted synthesis and conventional hydrothermal method, comprising of well-crystallized a...

To work against the volume expansion (∼300%) of SnO2 during lithiation, here a sub-micro sized, interconnected, and porous SnO2 cube with rationally designed reserved space (∼375%) is synthesized via an artful topochemistry route (CaSn(OH)6-CaSnO3-SnO2). Owing to its microstructure, this novel material harvests enhanced lithium-storage performance.

In the search of high-performance anode materials for next-generation Li-ion batteries, more efforts are needed on new structural prototypes. Motivated by the negative thermal expansion effect in a loosely packed crystal structure type, we are intrigued by the possibility of exploiting new anode materials in a suitable phase structure with much-reduced intrinsic volume strain. Herein, we report a new pyrochlore phase anode material, Ce2Sn2O7, which shows atomic Sn confined in a conductive 3D percolating Ce–O framework. Based on the concept of structural openness, pyrochlore Ce2Sn2O7 possesses open structures to tolerate the volume change. Notably, the Ce–O network is quite robust against the charge/discharge process, which accounts for the high structural stability observed in the experiment. Ultimately, Ce2Sn2O7 electrodes achieve a capacity as high as 631.1 mA h g−1 and excellent cycling stability. This atom-confining strategy of atomic Sn in the conductive 3D percolating Ce–O framework might be exploited as a general strategy for reducing cycling strain in ion-storage materials.

Flexible electrode materials toward rational design and low-cost fabrication are crucial to energy storage applications. Herein, a three-dimensional (3D) flexible N, B co-doped carbon foam (NBC) is developed, enabling efficient polysulfides confinement. N, B co-doping is employed to overcome the conflict between heteroatom doping and stability of carbon lattice, because one B and one N atoms are isoelectronic to two C atoms. B atoms in such a carbon structure possess positive charge which can interact with Sn2− anions in forming Sn2− … B while N atoms form negative charge which construct a strong-couple interaction with Li+ cations in forming N⋯Li2Sn. Moreover, the fabrication approach of corresponding flexible 3D carbon form is extremely facile derived from the self-gelation of agar. When used as the host for S, such a 3D carbon foam provides a continuous conductive structure, accommodates the volume change during long-term cycling and serves as a barrier for polysulfides dissolution. As a result, cycling performance of high sulfur loading (5.8 mg cm−2) NBC-S electrode exhibits high areal capacity of 5.6 mA h cm−2 (965 mA h g−1) with a very small capacity decay of 0.03% per cycle over 350 cycles at 0.2 C.

Chemical activation has been widely used to synthesize porous carbon materials due to its promising application on energy storages. To ensure the sufficient activation, heavily usage of activation agent is necessary, which is unsafe and uneconomical for massive production. Here a sol-gel assisted chemical activation strategy was proposed to synthesize nitrogen doped porous carbon material. The sol-gel process ensured the activation agent uniformly mixed with carbon precursors, which achieved sufficient activation at a quietly low consumption of activation agent. As synthesized carbon material possesses high specific surface area (2140 m2/g) and N, O content (5.42 at.% and 11.29 at.%). Electrochemical characterization shows that the material delivers a capacitance of 334 F/g in 1 M H2SO4 electrolyte. The sol-gel assisted chemical activation is a promising strategy to synthesize low-cost nitrogen doped porous carbon materials.

Black TiO2-x attracts enormous attention due to its large solar absorption and improved conductivity. In this work, a novel structure of TiO2-x with conductive TiO layer, performing full-spectrum absorption, was synthesized in one step by the unforeseen dismutation reaction of titanium sub-oxides (Tin O2n-1 ) in ammonium halide atmosphere. For this new reaction, a possible mechanism of decomposition-etching-disproportionation-rehydrolysis process was proposed. The vital intermediate reactant TiCl4 , which verifies the assumption, has been captured in the form of (NH4 )2 TiCl6 , especially where Ti2 O3 is the reactant. Furthermore, this work not only can nominate TiO as an alternative for noble metals or carbon materials in the aim to improve the electron conductivity and solar absorption of black TiO2-x , which are important in electrochemistry and optoelectronics fields, but also can be a new route to synthesize special structures for other multivalent transition metals.

In this study, in situ synthesis of carbon-coated MoC1–x nanodots anchored on nitrogen-doped carbon (MoC1–x@C) for lithium storage is reported. The obtained MoC1–x@C hybrids exhibit intriguing stru...

Nitrogen-rich carbon materials attract great attention because of their admirable performance in energy storage and electrocatalysis. However, their conductivity and nitrogen content are somehow contradictory because good conductivity requires high-temperature heat treatment, which decomposes most of the nitrogen species. Herein, we propose a facile method to solve this problem by introducing boron (B) to fix the nitrogen in a three-dimensional (3D) carbon material even at 1000 °C. Besides, this N-rich carbon material has a high content of pyrrolic nitrogen due to the selective stabilization of B, which is favorable in electrochemical reactions. Density functional theory (DFT) investigation demonstrates that B reduces the energy level of neighboring N species (especially pyrrolic nitrogen) in the graphene layer, making it difficult to escape. Thus, this carbon material simultaneously, achieves high conductivity (30 S cm-1) and nitrogen content (7.80 atom %), thus showing an outstanding capacitance of 412 F g-1 and excellent rate capability.

Titania with intrinsic safety (without lithium deposition) has met the safety requirement for high-power batteries, however, its poor rate capability due to sluggish ion diffusion coefficients remains as a challenge. Here mesoporous structure titania with a fast ion-conducting surface layer through lithiation can achieve capacitive lithium storage: 220 mA h g−1 at 1 C, 114 mA h g−1 at 50 C, 93 mA h g−1 at 100 C. The improvement in rate performance can be attributed to two factors: The resulting lithiated titania shows over 5 orders of magnitude improvement of conductivity (from 0.001 to 198.20 μS cm −1) induced by the presence of bulk Ti3+ , enabling an ultra-fast conduction path for electrons; The lithiated surface layer is favorable to faster lithium ion transport, addressing the limited lithium diffusion between the electrolyte and the active electrode materials. This new route may offer a general approach towards lithium batteries with capacitor-like rate performance.

To achieve large-scale preparation of high-performance carbon materials for electrochemical energy storage with a simple and cost-effective method remains a challenge. Here, we report a novel approach to synthesize hierarchical porous carbon with a low melting point metal tin (Sn) as pore forming agent. An aqueous processed tin chloride-polyethylene glycol (SnCl2-PEG) gel is used as precursor to form Sn/Carbon (Sn/C) composites with homogeneously distributed ultrafine Sn particles (

Selections of metallic cathode materials and modulations of metal–sulfur bonding strength are crucial for sulfur immobilization in development of high-performance lithium–sulfur (Li–S) batteries with low cost. By combining theoretical calculations and experiments, herein we reveal the relationship between intrinsic electronic structure and metal–S bonding strength, which links to energy density and durability of Li–S batteries. Through first-principles calculations, we simulate sulfur clusters (S1, S2, S4, and S8) immobilization on metal (Cu, Ni, and Sn) slab surfaces with and without graphene substrate. For sulfur clusters, the metal–Sx (x = 1, 2, 4, and 8) bonding strength is in the sequence of Ni > Cu > Sn without graphene substrate. Nevertheless, the sequence changes (Ni > Sn > Cu) in the presence of graphene substrate due to different amounts of charge transfer between these metal clusters and graphene. Guided by these theoretical results, metal (Cu, Ni, Sn)/graphene (G) composites are synthesized an...

Nitrogen-doped hollow carbon spheres with a well-defined shape, uniform diameter, and high doping concentration (11 at%) are synthesized via space-confined thermal decomposition of a single source precursor zinc carbodiimide, which can serve as both carbon and nitrogen sources and also a self-template.

Layered transition metal dichalcogenides (TMDs) such as MoS2 have attracted considerable interest as two-dimensional materials because of their unique physical and chemical properties. Single or few-layer TMD nanosheets can be achieved by conventional Li intercalation methods through organolithium chemistry or electrochemistry. However, these methods are hampered by the low yield, mixed phases and a lot of defects inside the nanosheets. Here we develop a novel general strategy to prepare single-layer TMD nanosheets by using AMS2 (A = Li, Na, K; M = Mo, Nb, Ta, Ti) crystals as ideal precursors. The crystal structure of these compounds ensures the robust S–M–S layers and fully filled alkali atoms between them, which lead to a high-yield production of high-quality single-layer nanosheets by following chemical exfoliation. Surprisingly, MoS2 nanosheets obtained by LiMoS2 crystals show a high-quality 1T′ phase, while the widely used n-butyl lithium method can only prepare phase-mixed (2H, 1T, 1T′) nanosheets with abundant defects. The as-prepared 1T′ MoS2 nanosheets exhibit a remarkable electrical conductivity (618 S cm−1), which is much higher than that of MoS2 nanosheets (35.4 S cm−1) obtained using the n-butyl lithium method, also the highest value in MoS2 related materials and superior to the best value of the reported 2D films of graphene (550 S cm−1).

Jahn-Teller distorted Mn(III) (t2g3eg1) ions play a key role in the performance of manganese-based layered oxides. Here we show that there is an obvious relationship between the Jahn-Teller distortion of a trivalent manganese and the electrochemistry in a pair of Na isomer, namely orthorhombic and hexagonal P2-type Na2/3Mn0.9Ti0.1O2 having the same composition. It is found that more reversible phase transformations, higher working voltage and faster Na diffusion correlated with Jahn-Teller effect are found for distorted P′2-Na2/3Mn0.9Ti0.1O2 upon Na+ ions extraction/insertion. Such Jahn-Teller distorted Mn assisted Na migration enables that the orthorhombic Na2/3Mn0.9Ti0.1O2 delivers a high specific capacity of 204.0 mA h g−1 with a 2.7 V average working voltage, reaching 550 Wh Kg−1 with both better cycle stability (a capacity retention of 82.3% after 100 cycles) and enhanced rate capability (97.8 mA h g−1 cycled at 10C) in Na cell in contrast with undistorted Na2/3Mn0.9Ti0.1O2. This strategy for understanding the Jahn-Teller effect of P2-type compounds at orbital energy level grasps new insight into designing high energy density positive electrode materials for Na-ion batteries.

Nitrogen-doped hierarchical porous hard carbon (NPC) that are capable of high N content, high specific surface area and high chemical stability has the potential to be a promising electrode material for energy storage application. Here we report a N-doped hierarchical porous hard carbon via a facile Ti-peroxy initiated in-situ polymerization of p-phenylenediamine. Ti-peroxy can also serve as a hard template to manipulate the formation of hierarchical porous. This nitrogen-doped hierarchical porous hard carbon has advantages of high N-content (7.2 at. %) and high surface area (1515 m2 g−1), displaying a specific capacitance of 360 F g−1 and an extraordinary cycling stability above 98% after 30,000 cycles.

Binary oxides MO2 (M = Ti, Sn) are promising anode materials for Li-ion batteries, but they suffer from rather low capacities (TiO2: ∼340 mA h g−1) and poor cycling stability (SnO2

To utilize visible-light solar energy to meet environmental and energy crises, black TiO2 as a photocatalyst is an excellent solution to clean polluted air and water and to produce H2. Herein, black TiO2 with a crystalline core–amorphous shell structure reduced easily by CaH2 at 400 °C is demonstrated to harvest over 80 % solar absorption, whereas white TiO2 harvests only 7 %, and possesses superior photocatalytic performances in the degradation of organics and H2 production. Its water decontamination is 2.4 times faster and its H2 production was 1.7 times higher than that of pristine TiO2. Photoelectrochemical measurements reveal that the reduced samples exhibit greatly improved carrier densities, charge separation, and photocurrent (a 4.5-fold increase) compared with the original TiO2. Consequently, this facile and versatile method could provide a promising and cost-effective approach to improve the visible-light absorption and performance of TiO2 in photocatalysis.

Nano TiO2 is investigated intensely due to extraordinary photoelectric performances in photocatalysis, new-type solar cells, etc., but only very few synthesis and physical properties have been reported on nanostructured TiO or other low valent titanium-containing oxides. Here, a core-shell nanoparticle made of TiO core covered with a ≈5 nm shell of amorphous TiO1+x is newly constructed via a controllable reduction method to synthesize nano TiO core and subsequent soft oxidation to form the shell (TiO1+x ). The physical properties measurements of electrical transport and magnetism indicate these TiO@TiO1+x nanocrystals are a type-ІІ superconductor of a recorded Tconset = 11 K in the binary Ti-O system. This unusual superconductivity could be attributed to the interfacial effect due to the nearly linear gradient of O/Ti ratio across the outer amorphous layer. This novel synthetic method and enhanced superconductivity could open up possibilities in interface superconductivity of nanostructured composites with well-controlled interfaces.

Conductive carbon nitride, as a hypothetical carbon material demonstrating high nitrogen doping, high electrical conductivity, and high surface area, has not been fabricated. A major challenge towards its fabrication is that high conductivity requires high temperature synthesis, but the high temperature eliminates nitrogen from carbon. Different from conventional methods, a facile preparation of conductive carbon nitride from novel thermal decomposition of nickel hydrogencyanamide in a confined space is reported. New developed nickel hydrogencyanamide is a unique precursor which provides self-grown fragments of ⋅NCN⋅ or NCCN and conductive carbon (C-sp2) catalyst of Ni metal during the decomposition. The final product is a tubular structure of rich mesoporous and microporous few-layer carbon with extraordinarily high N doping level (≈15 at%) and high extent of sp2 carbon (≈65%) favoring a high conductivity (>2 S cm−1); the ultrahigh contents of nongraphitic nitrogen, redox active pyridinic N (9 at%), and pyrrolic N (5 at%), are stabilized by forming NiN bonds. The conductive carbon nitride harvests a large capacitance of 372 F g−1 with >90% initial capacitance after 10 000 cycles as a supercapacitor electrode, far exceeding the activated carbon electrodes that have

Hydrogenated black titania, with a crystalline core/amorphous shell structure, has attracted global interest due to its excellent photocatalytic properties. However, the understanding of its structure–property relationships remains a great challenge and a more effective method to produce hydrogenated titania is desirable. Herein, we report a TiH2 assisted reduction method to synthesize bluish hydrogenated titania (TiO2−x:H) that is highly crystallized. The characteristic amorphous shells, which are essential for the enhancement of solar absorption and photocatalysis in many reported hydrogenated titania, are completely removed by hydrogen peroxide. The blue TiO2−x:H sample without amorphous shells delivers not only significantly improved visible- and infrared-light absorption but also greatly enhanced photocatalytic activity compared to pristine TiO2. Its water decontamination is 2.5 times faster and the hydrogen production was 1.9-fold higher over pristine TiO2. Photoelectrochemical measurement reveals greatly improved carrier density and photocurrent (a 4.3-fold increase) in the reduced TiO2−x:H samples. This work develops a facile and versatile method to prepare hydrogenated titania and proposes a new understanding of the hydrogenated titania that doped hydrogen atoms, instead of the amorphous shells, are essential for its high photocatalytic performance.

A new catalyst (Ni/Mo/MgO) is reported, with which one can synthesize multi-walled carbon nanotube (MWNT) bundles with a yield of more than 45 times the amount of the pristine catalyst, using a methane-hydrogen mixture as precursor. Powder X-ray diffraction, Raman spectroscopy and thermal gravimetric analysis show that the purity of the as-prepared MWNTs is over 97%. The diameter of the carbon nanotubes is 9–20 nm, measured by high-resolution electron microscopy on 421 individual MWNTs. The high purity of the as-prepared MWNTs allows us to omit the usual complex purification process required for carbon nanotubes synthesized by chemical vapor deposition. Because of its durable high activity, the Ni/Mo/MgO catalyst in its pristine state is ideal for mass production of high-quality MWNTs. The synergism of nickel and molybdenum is considered the main reason for the high yield of carbon nanotubes.

SnO2 -based lithium-ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO2-x , which homogenizes the redox reactions and stabilizes fine, fracture-resistant Sn precipitates in the Li2 O matrix. Such fine Sn precipitates and their ample contact with Li2 O proliferate the reversible Sn → Li x Sn → Sn → SnO2 /SnO2-x cycle during charging/discharging. SnO2-x electrode has a reversible capacity of 1340 mAh g-1 and retains 590 mAh g-1 after 100 cycles. The addition of highly conductive, well-dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g-1 remaining after 100 cycles at 0.2 A g-1 with 700 mAh g-1 at 2.0 A g-1 . Conductivity-directed microstructure development may offer a new approach to form advanced electrodes.