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Adsorption is often time consuming due to slow diffusion kinetic. Sizing he adsorbent down might help to accelerate adsorption. For CoFe spinel oxide, a magnetically separable adsorbent, the preparation of nanosheets faces many challenges including phase separation, grain growth and difficulty in preparing two-dimensional materials. In this work, we prepared porous CoFe oxide nanosheet with chemical formula of Co 2.698 Fe 0.302 O 4 through topochemical transformation of a CoFe precursor, which has a layered double hydroxide (LDH) analogue structure and a large interlayer spacing. The LDH precursor was synthesized from a cheap deep eutectic solvent (DES) system. The calcined Co 2.698 Fe 0.302 O 4 has small grain size (10–20 nm), nanosheet morphology, and porous structure, which contribute to a large specific surface area of 79.5 m 2 g −1 . The Co 2.698 Fe 0.302 O 4 nanosheets show fast removal ability and good adsorption capacity for both organic waste (305 mg g −1 in 5 min for Congo red) and toxic heavy metal ion (5.27 mg g −1 in 30 min for Cr (VI)). Furthermore, the Co 2.698 Fe 0.302 O 4 can be separated magnetically. Considering the precursor can be prepared through a fast, simple, surfactant-free and high-yield synthetic strategy, this work should have practical significance in fabricating adsorbents. [ABSTRACT FROM AUTHOR]

Manganese oxides with desired structure are controllably obtained through annealing MnCO 3 precursors with required structures. The structures of MnCO 3 precursors are determined by a “mesocrystal formation” process in an ionic liquid system of a choline chloride/urea (CU) mixture. Without addition of surfactants, only CU solvent and manganese chloride are needed in the reaction system, in which the CU acts as reaction medium as well as control agent for particle growth. A shape transformation of MnCO 3 particles from well-defined rhombohedral mesocrystals to ellipsoidal polycrystal ensembles, and to nanoparticulate aggregates is observed when heating the reaction system for 4 h at 120, 150, and 180 °C, respectively. With a longer aging time at 120 °C, etching and disassembly of MnCO 3 mesocrystals happened. The correlation between the microstructure and the underlying formation mechanism is highlighted. Porous and nanowire-like MnO x nanostructures are obtained through a facile thermal conversion process from the diverse MnCO 3 precursors, which are demonstrated as effective and efficient adsorbents to remove organic waste (e.g. Congo red) from water. Significantly, the nanowire-like MnO x nanostructures obtained by annealing the MnCO 3 mesocrystals at 300 °C for 4 h can remove about 95% Congo red in waste water at room temperature in only one minute, which is superior to the reported hierarchical hollow nanostructured MnO 2 . [ABSTRACT FROM AUTHOR]

Polypyrrole-coated high Na content Na 0.91 MnO 2 porous microcubes are prepared through high temperature calcination followed by a chemical ice water bath process. The higher sodium content of Na 0.91 MnO 2 makes capacity increase up to 50 mAh g−1 compared with Na 0.7 MnO 2.05. The thus wider interlayer space makes ion/electron insertion/extraction faster. Porous structure providing shorter ion/electron diffusion distance compared with hollow sphere structure. The conductive polymer modified sodium manganate oxide cathode for sodium ion full batteries exhibits ultrahigh initial capacity, cycling stability and rate capability. Highly conductive cathode material with enhanced Na+ diffusion kinetics is of great importance in the exploration of sodium ion batteries. In this work, Na 0.91 MnO 2 porous microcube which is coated with highly conductive polypyrrole (PPy) is obtained. The high Na content in the layered sodium manganate oxide brings about wider interlayer distance resulting in high capacity and electrochemical kinetics. The higher sodium content of Na 0.91 MO 2 makes capacity increase up to 50 mAh g−1 compared with Na 0.7 MnO 2.05. Furthermore, the well-designed combination between porous structure and conductive PPy coating exhibits fast ion/electron transfer inside the electrode and high cycling stability. The PPy coated Na 0.91 MnO 2 delivers a high initial capacity of 208 mAh g−1, encouraging capacity retention and rate capability. Based on the porous Na 0.91 MnO 2 @PPy cathode, the sodium ion full cells with puffed millet porous carbon anode show remarkably stable cycling and high-rate performances. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO 2) has been widely used as an anode material for sodium-ion storage because of its high theoretical capacity. However, it suffers from large volume expansion and poor conductivity. To overcome these limitations, in this study, we have designed and prepared Mo-doped SnO 2 nanoflake arrays anchored on carbon foam (Mo-SnO 2 @C-foam with 38.41 wt% SnO 2 and 3.7 wt% Mo content) by a facile hydrothermal method. The carbon foam serves as a three-dimensional conductive network and a buffer skeleton, contributing to improved rate performance and cycling stability. In addition, Mo doping enhances the kinetics of sodium-ion transfer, and the interlaced SnO 2 nanoflake arrays is beneficial to promote the conversion reactions during the charge/discharge process. The as-prepared composite with a unique structure demonstrate a high initial capacity of 1017.1 mAh g−1 at 0.1 A g−1, with a capacity retention over three times higher than that of the control sample (SnO 2 @C-foam) at 1 A g−1, indicating a remarkable rate performance. [ABSTRACT FROM AUTHOR]

Improving the insulating nature of sulfur and retaining the soluble polysulfides in sulfur cathodes are crucial for realizing the practical application of lithium–sulfur batteries (LSBs). Biomass-based carbon is becoming increasingly popular for fabricating economical and efficient cathodes for LSBs owing to its unique structure. Herein, we report a facile strategy to transform bovine bone with an organic–inorganic structure into cellular hierarchical porous carbon via carbonization and KOH activation, followed by CoS 2 modification through hydrothermal treatment. The synthesized composite can load abundant sulfur and produce a dual effect of "physical confinement and chemical entrapment" on polysulfides. The conductive carbon frame with the developed porous structure provides adequate space to accommodate sulfur and physically suppress the shuttle effect of polysulfides. The embedded half-metallic CoS 2 sites can chemically anchor the polysulfides and enhance the electrochemical reaction activity as well. Owing to the multifunctional structure and dual restraint effect, the designed electrode exhibits enhanced electrochemical properties including high initial capacity (1230.9 mAh g−1 at 0.2 C), improved cycling stability and enhanced rate capability. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO 3 mesoporous films as integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO 3 based films are significantly influenced by doping concentration. Compared with the pure WO 3 , the optimal Nb-doped film shows improved optical-electrochemical properties with high specific capacity (74.4 mAh g−1 at 2 A g−1), excellent high-rate capability, large optical contrast (61.7% at 633 nm), and ultra-fast switching speed (3.6 s and 2.1 s for coloring and bleaching process, respectively). These positive features suggest the potential application of Nb-doped WO 3 mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices. [ABSTRACT FROM AUTHOR]

Metal-doping is considered to be an effective way for construction of advanced semiconducting metal oxides with tailored physicochemical properties. Herein, Mo-doped WO 3 nanowire arrays are rationally fabricated by a sulfate-assisted hydrothermal method. Compared to the pure WO 3 , the optimized Mo-doped WO 3 nanowire arrays exhibit improved electrochromic properties with fast switching speed (3.2 s and 2.6 s for coloration and bleaching, respectively), significant optical modulation (56.7% at 750 nm, 83.0% at 1600 nm and 48.5% at 10 μm), high coloration efficiency (123.5 cm 2 C −1 ) and excellent cycling stability. In addition, as a proof of concept, the Mo-doped WO 3 nanowire arrays are demonstrated with electrochemical energy storage monitored by the electrochromism. This electrode design protocol can provide an alternative way for developing high-performance active materials for bi-functional electrochromic batteries. [ABSTRACT FROM AUTHOR]

High-performance electrochromic films with large color contrast and fast switching speed are of great importance for developing advanced smart windows. In this work, crystalline/amorphous WO 3 core/shell (c-WO 3 @a-WO 3 ) nanowire arrays rationally are synthesized by combining hydrothermal and electrodeposition methods. The 1D c-WO 3 @a-WO 3 core/shell hierarchical structures show a synergistic effect for the enhancement of optical modulation, especially in the infrared (IR) region. By optimizing the electrodeposition time of 400 s, the core/shell array exhibits a significant optical modulation (70.3% at 750 nm, 42.0% at 2000 nm and 51.4% at 10 μm), fast switching speed (3.5 s and 4.8 s), high coloration efficiency (43.2 cm 2 C −1 at 750 nm) and excellent cycling performance (68.5% after 3000 cycles). The crystalline/amorphous nanostructured film can provide an alternative way for developing high-performance electrochromic materials. [ABSTRACT FROM AUTHOR]