Ferrites with superstructures exhibit great potential for gas sensing applications, benefiting from their open structure, high specific surface area, and fully exposed active sites. However, the preparation of these superstructures is often cumbersome and requires some surfactants. In this study, Zn-Fe Prussian blue analogue (PBA) nanocages were synthesized through Ostwald ripening using a simple liquid-phase coprecipitation method without any other etchants or surfactants. A series of MFe2O4 (M = Fe, Co, Ni, Cu) nanocages, including n-type and p-type semiconductors, were obtained using the Zn-Fe PBA nanocages as templates via a metal ion exchange strategy and annealing process. Gas sensing investigations revealed that Zn-CuFe2O4, Zn-Fe3O4, and Zn-CoFe2O4 materials exhibited high sensitivity and selectivity for H2S, ZnFe2O4 for H2, and Zn-NiFe2O4 for NO2 at relatively low operating temperatures (50-150 °C). Quasi-in situ X-ray photoelectron spectroscopy and in situ infrared spectroscopy analyses indicated that during the H2S sensing response process, H2S reacted with the adsorbed oxygen on the surface of Zn-doped Fe3O4 and CuFe2O4 materials, as well as with the materials themselves, resulting in the formation of metal sulfide intermediates in small quantities. This work advances the controllable preparation of nanosuperstructures and lays a sound foundation for their widespread applications.

The rational integration of nanomaterials with different functions is a new solution to improve the gas-sensing performance of metal oxide gas sensors. In this paper, Fe2O3 nanotube-decorated ZnFe2O4 open nanocages and nanoboxes with a hierarchical complex superstructure are prepared by an autotemplate epitaxial growth strategy combined with an annealing process. The gas sensitivity test result shows that the Fe2O3 nanotube-decorated ZnFe2O4 open nanocage exhibited good gas selectivity for H2S at a relatively low operating temperature (140 °C) with fast response/recovery time (12/96 s) and a detection limit as low as 39 ppb. The superior gas-sensing performance of Fe2O3 nanotube-decorated ZnFe2O4 open nanocages is attributed not only to the combination of open cavities and porous shell structures but also to the highly active tubular Fe2O3 subunits with ultrathin wall thickness to promote the adsorption of gas molecules and the migration of carriers. Quasi in situ X-ray photoelectron spectroscopy and in situ infrared characterization reveal that H2S is physically adsorbed in an unstable state on the surface of the Fe2O3-nanotube-decorated ZnFe2O4 open nanocages during the gas-sensing response. This unstable adsorption facilitates faster desorption, thereby significantly reducing the sensor's response/recovery times. This work not only provides a novel strategy for designing high-performance H2S gas-sensing materials but also proposes a promising approach for engineering complex nanostructures with enhanced functionalities.

Nanoframes have broad application prospects in the field of gas sensor due to their large specific surface area and fully exposed active sites. However, due to the presence of the solid edge, traditional nanoframes cannot maximize the exposure of the material's active sites, which hinders the charge and mass transfer processes during gas sensing. Hitherto, there have been no reports of hollow-edge frame material. In this work, Zn/Fe co-doped SnO2 ultra-thin hollow-edge nanoframes are prepared for the first time, which have a huge specific surface area (520.19 m2 g-1) and exhibit an excellent gas sensing performance for hydrogen sulfide (H2S) gas at a relatively low operating temperature (130 degrees C). Quasi-in-situ X-ray photoelectron spectroscopy and in-situ infrared spectrometer confirmed that H2S gas reacted not only with the adsorbed oxygen on the material's surface, but also with the material itself during the gas sensing response. The density functional theory calculations provide theoretical support for the excellent selectivity of Zn/Fe co-doped SnO2 ultrathin hollow-edge nanoframes towards H2S. This work provides a new perspective for further expanding the complexity of nanoframes.

Metal-oxide semiconductor is widely applied in gas sensor for volatile organic compound detection. However, these sensors usually exhibit poor selectivity and inferior sensitivity. Here, ZnO@Fe2O3 microflowers were synthesized using FeOOH microflowers as precursors via a simple solution reaction route, followed by heat treatment. The ZnO@Fe2O3 microflowers were characterized using a series of techniques, and their sensing responses to volatile organic compounds (VOCs) were evaluated in comparison with those of pristine Fe2O3. The ZnO@Fe2O3 microflower sensor exhibited better responses to several gases, especially acetone, with a response of 74.3 towards 100 ppm acetone, which is 2.85 times higher than that of the Fe2O3 microflower sensor. The sensor also presented high selectivity, reproducibility, and stability in sensing different VOCs. The large specific surface area, heterostructure, favorable hierarchical flower-like nanostructure assembled by the nanosheets, and high porosity of the ZnO@Fe2O3 microflowers contributed to its enhanced gas-sensing responses. Overall, this synthetic strategy for fabricating flower-like ZnO@Fe2O3 nanostructures can be widely applied.

Metal oxide semiconductor (MOS) nanostructures are used widely in acetone sensors, but pure MOS sensors usually have poor selectivity and low sensitivity. In this study, various Sn-doped Fe2O3 (Sn-Fe2O3) microflowers were obtained using FeOOH microflowers as precursors using a liquid hydrolysis reaction followed by a calci-nation process. Various characterization techniques verified the morphologies and composition of the products. The microflower-like 17.0 wt% Sn-Fe2O3 possessed a specific surface area of 138.9 m2 g-1. Employed as a sensing material, the 17.0 wt% Sn-Fe2O3 microflowers exhibited a strong response of 107.7 for 100 ppm acetone with short response/recovery times of 8/12 s. Furthermore, the 17.0 wt% Sn-Fe2O3 microflower sensor displayed good selectivity and high stability for acetone vapor with a detection limit of 114 ppb. The in-situ Raman spectrum verified that the Sn-Fe2O3 microflowers improved the adsorption of the acetone molecules, resulting in enhanced sensing performance.

Transition metal oxides applied in anode for lithium-ion batteries are susceptible to particle aggregation during the cycling test, resulting in a low capacity retention during cycling process. In this study, Fe 2 O 3 /polyaniline microflowers were prepared via a simple liquid-phase oxidation and calcination process followed by polyaniline coating. Several characterization techniques demonstrated their morphology and chemical composition. When applied in anode for lithium-ion batteries, Fe 2 O 3 /polyaniline microflowers exhibit an ultrahigh specific capacity of 1847.1 mAh g-1 over 100 cycles at 0.1 A/g. A high specific capacity of 619.8 mAh g-1 was achieved after 300 cycles at 1.0 A/g. The high performance is mainly due to the polyaniline coating and flower-like microstructures, which can mitigate the volume change, improve the electrical conductivity and cycling stability, and contribute to the rapid Li + diffusion. This work provides a new route for synthesizing advanced-performance Fe 2 O 3-based anode material.

Lithium-sulfur (Li-S) batteries are promising candidates for large-scale high-energy-density devices owing to their potential high energy density, low cost, and more pronounced ecological compatibility. Nevertheless, their commercial applications of Li-S batteries are limited by the low electrical conductivity of sulfur, huge volume swell, shuttle effect, and slow redox reactions. In order to solve the above issues, various sulfur hosts have been developed and combined with active sulfur to form a composite. Polyaniline-coated cobalt nitride nanoflowers loaded with sulfur (CoN/S@PANI nanoflowers) were prepared by simple liquid phase precipitation followed by nitridation, sulfurization, and coating with polypyrrole. The CoN nanoflowers possessed a hierarchical nanostructure with a large specific surface area, which could reduce the volume swelling of sulfur and the shuttle effect of polysulfides. The polyaniline coating with high electrical conductivity can adsorb the polysulfides and promote the electrochemical reaction kinetics. Therefore, the CoN/S@PANI nanoflowers exhibit a high initial capacity of 895 mAh g-1 at 0.5 A g-1, which was kept at 736 mAh g-1 over 100 cycles. This paper reports a new route to prepare a sulfur host for advanced lithium-sulfur batteries.

The "shuttle effect" and slow redox reactions of Li-S batteries limit their practical application. To solve these problems, a judicious catalyst design for improved battery cycle life and rate performance is essential. Herein, this issue is addressed by modifying the Li-S battery separator using a 2D Fe2 O3 -CoP heterostructure that combines the dual functions of polar Fe2 O3 and high-conductivity CoP. The synthesized ultrathin nanostructure exposes well-dispersed active sites and shortens the ion diffusion paths. Theoretical calculations, electrochemical tests, and in situ Raman spectroscopy measurements reveal that the heterostructure facilitates the inhibition of polysulfide shuttling and enhances the electrode kinetics. A sulfur cathode constructed using the Fe2 O3 -CoP-based separator provides an astonishing capacity of 1346 mAh g-1 at 0.2 C and a high capacity retention of ≈84.5%. Even at a high sulfur loading of 5.42 mg cm-2 , it shows an area capacity of 5.90 mAh cm-2 . This study provides useful insights into the design of new catalytic materials for Li-S batteries.

Lithium-sulfur (Li-S) battery has attracted extensive attention owing to its high theoretical energy density, low cost, and environmental friendliness. On the other hand, there are also some scientific problems, such as volume expansion and the shuttle effect of polysulfides. Here, three-dimensional cross-linked N-doped carbon nanosheets (NCNs) loaded with aluminum nitride (AlN) nanoparticles were synthesized and used as sulfur hosts for Li-S battery. The AlN@NCNs nanocomposites greatly improved the cycling and rate performance of Li-S battery. The AlN@NCNs/S nanocomposites provided a stable discharge capacity of 507.4 mAh/g after 400 cycles at 0.5 A/g, with a Coulombic efficiency of up to 99 %. After 500 cycles at 1.0 A/g, the capacity kept at 435.2 mAh/g. The polar AlN nanoparticles have strong adsorption on polysulfides, which obviously relieve the shuttle effect of polysulfides. Therefore, combining nitrogen-doped carbon nanosheets with metal nitride nanoparticles enhanced the electrochemical performance of Li-S batteries.

Gallium oxide as an anode material for lithium-ion batteries has attracted attention because of its high specific capacity. As reported previously, N-doped carbon coated Ga2O3 nanopapers exhibited a high dis-charge capacity of 477 mAh g-1 after 200 cycles at 0.2 A g-1. But the rate performance and cycling stability of the Ga2O3-based anode still need to be improved. Herein, Ga2O3 nanotubes coated with N-doped carbon layers (Ga2O3/N-C NTs) were prepared using MoO3 nanorods as sacrificial templates followed by a poly-dopamine coating and heat treatment process. The resulting tubular structure provided cavities for volume changes of the Ga2O3 in the cycling process and shortened the migration path of Li ions and electrons. The N-doped carbon coated Ga2O3 NTs delivered a capacity of 1185.3 mAh g-1 after 100 cycles at 0.1 A g-1 and outstanding stability of 535.5 mAh g-1 after 500 cycles at 1.0 A g-1. This study supplies a novel method for preparing Ga2O3 anode materials to promote the performance of lithium-ion battery. (c) 2023 Elsevier B.V. All rights reserved.

The design engineering of a hierarchical bimetallic composite anode is a critical part of the high-perfor-mance lithium-ion battery. This study developed a one-step sulfurization route to prepare hierarchical Cu3SnS4-Cu2SnS3 hollow nanocapsules (CTS HNCs) using CuSn(OH)6 nanorods as sacrificial templates. The final Cu3SnS4-Cu2SnS3/N-doped carbon hollow nanocapsules (CTS/N-C HNCs) were obtained by coating the hollow nanocapsules with polydopamine, followed by calcination. As an anode material, the CTS/N-C HNC electrode demonstrated a high capacity (827.8 mAh g-1 at 0.2 A g-1 over 150 cycles), superior long-cycling performance (409.1 mAh g-1 at 1.0 A g-1 over 500 cycles) and outstanding rate performance (average discharge capacity of 374 mAh g-1 at 5.0 A g-1). Hence, the CTS/N-C HNCs composites with a hollow structure, outer assembled nanosheets, and N-doped carbon layer are conducive to controlled volume changes during the intercalation/deintercalation process and accelerate the electron/Li+ transport. Briefly, this research provides a facile strategy for constructing CTS-based hierarchical composites, contributing to the further development of LIBs.(c) 2022 Elsevier B.V. All rights reserved.

Hollow micro/nanostructures have attracted considerable interest for lithium storage because of their merits in alleviating volume expansion. This paper presents novel preparation method for hollow tin dioxide nano-spheres coated with an ultrathin N-doped carbon layer (SnO2@N-C) using MgSn(OH)6 nanospheres as sacrificial templates through the alkali etching, annealing, acid washing, polydopamine coating, and subsequent carbonization. The resulting hollow SnO2@N-C nanosphere anode exhibited good cycling stability (1154.2 mAh g(-1 )after 200 cycles at 0.2 A g(-1)) and good rate performance (791.8, 708.6, 595.9, 402.2, 234.1, and 80.7 mA h g(-1 )at 0.1, 0.2, 0.5 1, 2, and 5 A g(-1), respectively). In addition, a capacity of 734.2 mAh g(-1 )was obtained as the current density was back to 0.1 A g(-1). The superior electrochemical performance was ascribed to their hollow microstructure and ultrathin N-doped carbon coating.

Achieving ideal photoelectrochemical (PEC) water splitting efficiency for renewable chemical fuel generation is a highly preferable but a challenging target. To do so, much effort needs to be taken to investigate photoelectrodes. In this study, we report the amelioration of hematite (alpha-Fe2O3), which is a well-known semiconducting oxide suitable for PEC water oxidation. The Se-doped alpha-Fe2O3 nanowire array thin film on the fluorine-doped tin oxide substrate was synthesized by a facile one-step hydrothermal process followed by in situ two-step annealing at 823 and 1073 K. A photocurrent of 0.85 mA cm(-2) at 1.23 V versus RHE was achieved for the Se-doped alpha-Fe2O3 photoanode, which was more augmented than the undoped alpha-Fe2O3 photoanode (0.33 mA cm(-2)). The Mott-Schottky plot revealed that the carrier concentration of alpha-Fe2O3 was strongly increased through Se doping. Photovoltage and electrochemical impedance spectroscopy indicated that Se-doped alpha-Fe2O3 exhibited a stronger driving force and reduced charge transport resistance, which were crucial aspects for higher photocurrent. Our work highlights the importance of the nonmetal element dopant to improve the PEC performance of alpha-Fe2O3 via convenient preparation.

Tin dioxide nanotubes coated with ultrathin N-doped carbon film (N-doped SnO2/C NTs) are prepared through a sacrificial template method for the first time. It was employed as anodes for lithium-ion batteries (LIBs) and delivered a high reversible capacity of 909.5 mAh g(-1) at 0.5 A g(-1) after 200 cycles, outstanding stability 551.7 mAh g(-1) after 500 cycles at 1 A g(-1), and excellent rate performance of 1069.2 mAh g(-1) after 280 cycles. Such superior electrochemical performance is owning to the N-doped carbon coating which improved the conductivity of the NTs, which is essential for higher performance LIBs. The special designed whole nanotube structure provides extensive surface and pores to accommodate Li, meanwhile, prohibited the volume expansion during cycling test. The electrochemical performance of pouch- type cells further demonstrates the SnO2/C NTs as a promising candidate for LIBs anode. This study has shed a light on the LIB anode materials design and preparation and made such hollow nanostructured materials a potential candidate to replace commonly used graphite materials.

A self-sacrificing template method is a common and straightforward way to synthesize hollow nanomaterials. In this study, a self-sacrificing template method was used for the facile preparation of well-defined hollow SnO2@C nanoboxes. CaSn(OH)(6) nanocubes, as sacrificial templates, reacted with glucose under hydrothermal conditions to synthesize hollow SnO2 nanoboxes. The surface of the hollow SnO2 nanoboxes via the carbonization of polydopamine, resulting in hollow SnO2@C nanoboxes. The electrochemical performance test confirmed the excellent rate performance (806.5, 785.0, 718.8, 612.4, and 297.8 mA h g(-1) at 0.1, 0.2, 0.5 1.0, and 2.0 A g(-1), respectively) and outstanding reversible capacity (786.9 mAh g(-1) after 100 cycles) of the hollow SnO2@C nanoboxes. The carbon-coated hollow structured SnO2 nanoboxes provide buffer space for volume expansion, high electrolyte contact area, and short ion transfer path, resulting in improved cycling stability and rate performance.

Nanostructured SnO2 and ZnS have been proved to application prospects in lithium-ion battery. However, some severe challenges, such as rapid capacity decay due to volume expansion during the charge/discharge process and poor conductivity, limit their applications. Herein, a hollow cubic SnO2/ZnS@C composite was obtained using ZnSn(OH)(6) cubes as precursor via a hydrothermal reaction and a subsequent carbon coating process. Served as anode material, the SnO2/ZnS@C nanocubes exhibit an initial capacity of 1312.8 mAh g(-1) at 0.1 A g(-1), the coulombic efficiency reaches 73.1%, and it remains 753.5 mA g(-1) over 200 cycles. Moreover, rate capacities of SnO2/ZnS@C composite reach up to 818, 757 and 693 mAh g(-1) at 0.2, 0.5 and 1.0 A g(-1), respectively. The SnO2/ZnS@C nanocubes exhibit the superior performance due to the synergistic effect of Sn and Zn, the hollow structure and the carbon coating. (C) 2021 Elsevier B.V. All rights reserved.

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium-sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core-shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core-shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g(-1), which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer.

The polysulfide shuttle phenomenon of lithium‑sulfur batteries restricts their practical applications. Herein, polypyrrole-coated hollow zeolite microcakes are first synthesized to reduce the polysulfide shuttle. The large surface area of hollow zeolite microcakes can increase the amount of sulfur storage. Moreover, the special hollow zeolite microcakes with polypyrrole coating enhance sulfur utilization. Consequently, the as-prepared composite electrode deliveres a capacity of 753 mAh g−1 after cycling 200 times at 0.1 A g−1, and a capacity of 460 mAh g−1 after cycling 500 times at 0.5 A g−1, which are much higher than those of the hollow zeolite microcakes without polypyrrole coating. These electrochemical characteristics make the composite a prospective sulfur host for lithium‑sulfur batteries.

Manganese monoxide (MnO) nanowire@reduced graphene oxide (rGO) nanocomposites are synthesized using a simple hydrothermal method combined with a calcination process. The structural and morphological characterization of the composites indicates that the MnO nanowires homogeneously anchor on both sides of the cross-linked rGO. The nanocomposites exhibit a high surface area of 126.5 m(2) g(-1). When employed as an anode material for lithium-ion batteries, the nanocomposites exhibit a reversible capacity of 1195 mAh g(-1) at a current density of 0.1 A g(-1), with a high charge-discharge efficiency of 99.2% after 150 cycles. The three-dimensional architecture of the present materials exhibits high porosity and electron conductivity, significantly shortening the diffusion path of lithium ions and accelerating their reaction with the electrolyte, which greatly improves the lithium-ion storage properties. These excellent electrochemical performances make the composite a promising electrode material for lithium-ion batteries.

Simultaneously achieving a high conductivity and a good volume-change accommodation for sulfur cathode in lithium-sulfur batteries is highly required. Herein, we present a unique porous sulfur composite consisting of a porous sulfur particle coating with conductive hydrogel polypyrrole, which is prepared through a templated method. The pores inside the sulfur particles offer a good buffering space for the volume expansion of sulfur upon lithiation; while the external polypyrrole coating improves the conductivity and suppress the transfer of polysulfides. The porous sulfur@polypyrrole composite exhibits a capacity of about 900 mAh g(-1) after cycling for 100 times at 0.12 C, along with a good Coulombic efficiency around 99.9%, which is much better than the polypyrrole-coated non-porous sulfur particles and pure sulfur particles. When cycled for 500 times, the capacity fading rate is as low as 0.09% per cycle. After three rounds of rate-performance measurements, the capacity retention of the sulfur@polypyrrole at different rates remain above 97%. The density functional theory calculations and electrochemical impedance spectra demonstrate a polysulfide-adsorptive and a stable electric transportation surface of the sulfur@polypyrrole composite, respectively.