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Background: Crystal violet dye is stable and difficult to be biodegraded owing to the existence of the multiple aromatic rings of the crystal violet molecules. Removing crystal violet dye from the wastewater is a major challenge. Objective: The aim of the research is to synthesize barium carbonate/tin dioxide nanoparticles and investigate the photocatalytic performance for the degradation of crystal violet. Methods: Barium carbonate/tin dioxide nanoparticles were synthesized via a facile hydrothermal route without any surfactants. The crystal structure, micro-morphology, size and optical performance of the barium carbonate/tin dioxide nanoparticles were investigated by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and solid ultraviolet-visible diffuse reflectance spectrum. Results : The size of the barium carbonate/tin dioxide nanoparticles is 20 nm to 200 nm with the band gap of 3.71 eV. The photocatalytic activity of the barium carbonate/tin dioxide nanoparticles was measured by the photocatalytic degradation of crystal violet. The crystal violet degradation efficiency reaches 92.1% with the ultraviolet-visible irradiation time of 8 h using 10 mg barium carbonate/tin dioxide nanoparticles. The crystal violet degradation ratio increases to 96.1% when the dosage of the barium carbonate/tin dioxide nanoparticles increases to 20 mg/10 mL crystal violet dye solution. Active species capture photocatalytic experiments showed that the holes, hydroxyl radicals and superoxide ion radicals are the main active species. Reusability experiments displayed that the barium carbonate/tin dioxide nanoparticles are stable for the crystal violet dye degradation. Conclusion: The barium carbonate/tin dioxide nanoparticles show good photocatalytic performance toward crystal violet under ultraviolet light irradiation.

Hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) have been considered as two critical processes in the field of electrocatalytic water-splitting for hydrogen production and fuel cells. However, the sluggish reaction kinetics of HER and ORR required efficient electrocatalyst such as Pt to promote such process. Transition metal phosphides (TMPs) exhibit great potential to replace noble metal electrocatalysts to accelerate HER and ORR due to their high activity and easy availability. Herein, a highly-efficient bifunctional CoP electrocatalyst for HER and ORR, featuring a unique core-shell structure decorated on nitrogen-doped carbon matrix was designed and constructed via etching a cobalt-based zeolitic imidazolate framework (ZIF-67) with phytic acid (PA) followed by pyrolysis treatment (PA-ZIF-67-900). Experimental results revealed that the pure-phase single-crystalline CoP exhibited outstanding electrocatalytic performance in HER and ORR, superior to Co(PO3)2 in PA-ZIF-67-700, hybrid phase of Co(PO3)2 and CoP in PA-ZIF-67-800 and Co2P-doped CoP in PA-ZIF-67-1000. To reach the current density of 10 mA/cm2 the as-synthesized CoP required an overpotential of 120 mV for HER in 1 M KOH and half-wave potential of 0.85 V in O2-saturated 0.1 mol/L KOH. This work present new clue for construction of efficient and bifunctional electrocatalyst in the field of energy conversion and storage

The development of cathode materials with a high electric conductivity and a low polarization effect is crucial for enhancing the electrochemical properties of magnesium-ion batteries (MIBs). Herein, Mo doping and nitrogen-doped tubular graphene (N-TG) introduction are carried out for decorating VS4 (Mo-VS4/N-TG) via the one-step hydrothermal method as a freestanding cathode for MIBs. The results of characterizations and density functional theory (DFT) reveal that rich sulfur vacancies are induced by Mo doping, and N-TG as a high conductive skeleton material serves to disperse the active material and forms a tight connection, all of which collectively improved the electrical conductivity of electrode and increased the adsorption energy of Mg2+ (-6.341 eV). Furthermore, the fast reaction kinetics is also confirmed by the galvanostatic intermittent titration technique (GITT) and the pesudocapacitance-like contribution analysis. Benefiting from the synergistic effect of electrical conductivity enhancement and rich vacancy introduction, Mo-VS4/N-TG delivers a steady Mg2+ storage specific capacity of about 140 mAh g-1 at 50 mA g-1, outstanding cycle stability (80.6% capacity retention ratio after 1200 cycles under 500 mA g-1), and excellent rate capability (specific capacity reaches 77.1 mAh g-1 when the current density reaches 500 mA g-1). In addition, the reversible reaction process, intercalation mechanism, and structural stability during the Mg2+ insertion/extraction process are confirmed by a series of ex situ characterizations. This research provides a sustainable and scalable strategy to spur the development of MIBs.

Titanium dioxide is often used to capture polysulfides due to its strong surface polarity. Surface activity of titanium dioxide is produced by defects, which possesses an important impact on abilities to capture polysulfides. However, the reaction mechanism of defective titanium dioxide in the process of capturing polysulfide is not clear. In this paper, we introduced cobalt source as an additive to titanium dioxide/biomass carbon composite materials to prepare titanium dioxide with many defects and strong surface activities. The crystallinity of biomass carbon surface is also continuously improved by introducing cobalt sources. Under combined performance of highly active titanium dioxide and highly conductive biomass carbon, composite materials possess strong and reversible polysulfide-capturing abilities. In particular, types of polysulfides captured is increased. Herein, the addition of cobalt source is beneficial to enhance abilities of titanium dioxide to capture multiple polysulfides, improve conductivity of composite materials and achieve high reversible capacity (375.0 mA h·g−1 after 500 cycles at 1C).

Polysulfides can be captured rapidly by defects, which possess strong catalytic redox abilities. Species of defects have important influence on rate performance of metal-sulfur electrodes. However, catalytic reaction mechanisms have not been explored in depth. This paper focuses on comparing differences between intrinsic defect carbon materials (IDC) and external introduced defect carbon materials (EIDC) in promoting polysulfide redox abilities and exploring catalytic redox reaction mechanism deeply. Results show that IDC have stronger catalytic redox reaction abilities than EIDC, which is mainly due to stable C–S bonds on surface of IDC. After cycling, C–S bond contents in IDC electrodes maintain more than 70 %. During cycling process, C–S bonds can quickly adsorb polysulfides and promote their conversion into final products, thereby achieving high rate performance. Weak catalytic redox abilities of EIDC electrodes is mainly due to loss of C–S bonds. When the current density is 5C, capacities of IDC electrodes is twice as much as that of EIDC electrodes. Good rate performance of IDC electrodes reflects important roles of stable C–S bonds in promoting redox reaction of polysulfides, which has important research significance for preparation of carbon-based composite electrodes.

Iron carbodiimide (FeNCN) belongs to a type of metal compounds with a more covalent bonding structure compared to common transition metal oxides. It could provide possibilities for various structural designs with improved charge-transfer kinetics in battery systems. Moreover, these possibilities are still highly expected for promoting enhancement in rate performance of sodium (Na)-ion battery. Herein, oriented FeNCN crystallites were grown on the carbon-based substrate with exposed {010} faces along the [001] direction (O-FeNCN/S). It provides a high Na-ion storage capacity with excellent rate capability (680 mAh g-1 at 0.2 A g-1 and 360 mAh g-1 at 20 A g-1), presenting rapid charge-transfer kinetics with high contribution of pseudocapacitance during a typical conversion reaction. This high rate performance is attributed to the oriented morphology of FeNCN crystallites. Its orientation along [001] maintains preferred Na-ion diffusion along the two directions in the entire morphology of O-FeNCN/S, supporting fast Na-ion storage kinetics during the charge/discharge process. This study could provide ideas toward the understanding of the rational structural design of metal carbodiimides for attaining high electrochemical performance in future.

The conversion chemistry of lithium–sulfur provides a high energy density (2600 Wh/kg), enabling lithium–sulfur batteries to be a promising energy storage system. Nevertheless, the dissolved lithiu...

To meet the ever-increasing demand for higher energy density and power density, developing cathode materials with high specific capacity has become an urgent problem. V2O5 has been considered as one of the most promising cathodes for its high theoretical specific capacity (443 mAh g−1), abundant source, and low cost. In this work, cobalt-doped vanadium pentoxide (Co-V2O5) microflowers were synthesized through a simple solvothermal method. The doped Co not only improves the electronic conductivity but also increases the diffusion coefficient of the lithium ions. Benefiting from the appropriate amount of Co doping, the charge transfer impedance decreases from 51 to 28 Ω and the diffusion coefficient of the lithium ions increased from 2.81×10−17 cm2 s−1 to 3.31×10−16 cm2 s−1. The optimal Co-V2O5 microflowers deliver a high reversible capacity of 166 mAh g−1 after 200 cycles.

Layer-structured α-MoO3 with high theoretical capacity (1117 mAh g−1) is considered as one of the alternative anode materials for LIBs. However, the repeated insertion/extraction of Li+ often causes irregularly exfoliated layer structure of α-MoO3, especially the multiple-direction interlayer Li+ insertion/extraction shows rapid capacity decay. In this work, we achieve regularly exfoliated layer structure by inducing [100]-orientated plate-like α-MoO3 during high-temperature calcinations process. This regularly exfoliated layer structure is dominated by the optimized [100] single-direction Li+ interlayer diffusion way caused by the induced orientation growth. As anode for LIBs, the plate-like α-MoO3 exhibits capacity retention of 86.7% from 1st to 300th, showing enhanced stability of Li storage performance. This work indicates that inducing orientation growth of electrode material to optimize lithium-ion diffusion path can achieve regular exfoliation of layer structure, which can enhance the stability of Li storage performance. This conclusion can be used as a good reference for enhancing stability of layer-structured electrodes by structure design.

The rational design and construction of noble-metal-free electrocatalysts with high activity and robust durability for oxygen evolution reactions (OERs) have aroused immense interest in the past decades, but challenges remain. Herein, a reduction-induced dissolution–recrystallization (RIDR) strategy was developed to fabricate a defect-rich yolk–shell Prussian-blue analogue (YS-PBA) by a solvothermal process in isopropyl alcohol (IPA) in the presence of polyvinylpyrrolidone (PVP). The experimental result indicated that the defect-rich YS-PBA was formed via phase transformation from Co3[FeIII(CN)6]2 to Co2FeII(CN)6 induced by the reduction potential of the IPA-PVP couple. The newly synthesized YS-PBA exhibited outstanding OER performance with a low overpotential of 293 mV to deliver a current density of 10 mA cm−2 and long-term durability (120 h) in alkaline media. Both experimental and density functional theory (DFT) results unveiled that the defects formed in YS-PBA cause a dramatic positive effect on the improvement of the OER activity.

The development of cost-effective, high-efficiency bifunctional electrocatalysts as alternatives to the state-of-the-art Pt-based materials toward the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is of great significance but still challenging. Herein, an advanced bifunctional electrocatalyst is presented, composed of Fe2P encapsulated in carbon nanowalls decorated with well-dispersed Fe3C nanodots (denoted as Fe2P@Fe3C/CNTs), which is achieved by a novel “inside-out” gas–solid reaction protocol. When functioning as a cathodic catalyst for water splitting, the Fe2P@Fe3C/CNT catalyst needs an ultralow overpotential of 83 mV to deliver a current density of 10 mA cm−2, shows a small Tafel slope of 53 mV dec−1 and ensures long-term stability for over 200 h in an alkaline electrolyte. Notably, the Fe2P@Fe3C/CNT catalyst exhibits an extremely impressive ORR performance with an onset potential (Eonset) of 1.060 V and a half-wave potential (E1/2) of 0.930 V, excellent stability (≈94% activity retention after 36 000 s), and a strong methanol resistance ability, even far outperforming commercial Pt/C (Eonset = 0.955 V, E1/2 = 0.825 V, ≈75% activity retention after less than 3500 s). Such outstanding HER and ORR performances are mainly ascribed to the improved corrosion resistance of the unique Fe2P@C core–shell structures, the abundant catalytically active sites of ultrasmall Fe3C nanodots incorporated in carbon nanowalls, and the good electrical conductivity of 2D graphitic carbon nanotubes used as a support.

We report the in situ generation of NiCoV-LTH on nickel foam for the HER. Interestingly, the introduction of Co into NiV-LDH can induce the formation of porous nanosheets to expose a large number of active sites and change the electron density around Ni and V to promote the absorption of hydrogen species and thus accelerate the HER kinetics.

Building composite structures of hollow metal sulfides and carbon material is considered an effective strategy for improving the performance of sodium storage. However, most of these composite structures are implemented using complex hard-templating and multiple-step methods. Moreover, the mechanism for enhancing the electrochemistry of carbon materials in hollow structures is not clear. In this work, a carbon-supported hollow tungsten disulfide (WS2) cuboid composite structure (marked H-WS2) was synthesized in one step by a self-templating method. On the one hand, the hollow composite structure can alleviate the volume changes during the charging and discharging processes, showing good structural stability. On the other hand, the pyrolytic carbon and nanosheet structure can effectively promote the transport of electrons/ions, exhibiting fast reaction kinetics. The H-WS2 electrode showed improved electrochemical performance for sodium storage. A high reversible capacity was achieved, 353.2 mA h g−1 after 100 cycles at 200 mA g−1. At a high current density of 5.0 A g−1, the reversible capacity of 236.7 mA h g−1 was still achieved. This work provides new insight into the synthesis of hollow metal sulfides and carbon composite structures.

In this work, the SnS2 nanoflakes electrode materials have been synthesized using citric acid as chelating agent for lithium-ions battery by a facile microwave hydrothermal method. Citric acid can form a strong ligand for metal ions, and the crystals growth is controlled by the interaction between ligand and hydrogen bond, which affects the nucleation, growth, and self-assembly in the synthesis process. Therefore, the SnS2 nanoflakes electrodes were obtained with the size and thickness of around 100–200 nm and ~ 30 nm, respectively. The SnS2 nanoflakes electrode delivers the initial discharge capacity of 1485.8 mAh g−1, the reversible capacity of 327.3 mAh g−1 at 100 mA g−1 after 100 cycles, and the Coulombic efficiency (CE) of about 99.8%. The prominent rate capability was exhibited for lithium-ion battery (387.5 mAh g−1 and 339.7 mAh g−1 at 800 and 1000 mA g−1, respectively). The outstanding electrochemical performance and high capacity retention rate mainly are ascribed to the fast charges, lithium-ions diffusion, and stable structure for SnS2 nanoflakes. This work could provide a potential approach to promote the electrochemical performances of sulfides electrode materials for lithium-ions battery.

Developing cost-effective, highly-active and robust electrocatalysts is of vital importance to supersede noble-metal ones for both hydrogen evolution reactions (HERs) and oxygen reduction reactions (ORRs). Herein, a unique vanadium-mediated space confined strategy is reported to construct a composite structure involving Co/Co9S8 nanoparticles anchored on Co–N-doped porous carbon (VCS@NC) as bifunctional electrocatalysts toward HER and ORR. Benefitting from the ultrafine nanostructure, abundant Co–Nx active sites, large specific surface area and defect-rich carbon framework, the resultant VCS@NC exhibits unexceptionable HER catalytic activity, needing extremely low HER overpotentials in pH-universal media (alkaline: 117 mV, acid: 178 mV, neutral: 210 mV) at a current density of 10 mA cm−2, paralleling at least 100 h catalytic durability. Notably, the VCS@NC catalyst delivers high-efficiency ORR performance in alkaline solution, accompanied with a quite high half wave potential of 0.901 V, far overmatching the commercial Pt/C catalyst. Our research opens up novel insight into engineering highly-efficient multifunctional non-precious metal electrocatalysts by a metal-mediated space-confined strategy in energy storage and conversion system.

Both biomass carbon and titanium dioxide are beneficial for enhancing the capturing capacities and conversion capacities of polysulfides and achieving excellent lithium–sulfur battery performance. However, the binding ability between highly polar titanium dioxide and weakly polar biomass carbon is weak. The sulfur-loading capacity of titanium dioxide/biomass carbon composite structures is limited and a large number of polysulfides produce shuttle effects. How to enhance the binding ability of titanium dioxide and biomass carbon to achieve high sulfur-loading is an issue that needed to be solved. In this paper, we introduce cobalt into the surface of titanium dioxide/biomass carbon composite structures, adjust the cobalt–titanium molar ratio and obtain composite structures with the strongest binding abilities. The composite structure has high specific capacity and good cycling stability. After 500 cycles at 1.7 A g−1, the reversible capacity is still close to 400 mA h g−1. The high capacity and good cycling stability depend on the ability of composite structures to capture multiple polysulfides and achieve reversible conversion.

The development of low-cost and high-efficient electrocatalysts toward hydrogen evolution reaction (HER) is highly desirable and challenging. Herein, the novel V-doped Ni3S2/NiS heterostructure nanorod arrays grown on nickel foam (VNS/NF-WM) are synthesized via a facile methanol-assisted hydrothermal method. We demonstrate that the morphology, phase composition, and crystallinity of VNS/NF are well modulated by tuning the ratios of water/methanol solvent. The optimized VNS/NF-WM-heterostructured nanorod (volume ratio of water/methanol is 3:1) exhibits superior HER electrocatalytic activity with low overpotentials of 85 and 218 mV to yield current density values of 10 and 100 mA cm-2, respectively, meanwhile sustaining an excellent stability with almost an unchanged current density of 10 mA cm-2 for 60 h. Our work offers fresh insights into the rational design of highly active and stable earth-abundant-heterostructured electrocatalysts for the hydrogen fuel production.

Ablation of carbon/carbon (C/C) composites was investigated in a nitrogen plasma torch with a heat flux of ∼25 MW/m2. The reaction products of carbon in C/C composites and nitrogen plasma jet were calculated based on the principle of free energy minimum. The calculated results show that the thermal chemical ablation and sublimation of carbon occur and Cn(g) (n = 1–3), CN(g), C2N(g) and C2N2(g) may be the major reaction products consuming carbon. Ablation is apt to begin at the interfaces, especially the fibre-matrix interface and interfaces inside the matrix. Ablation of C/C composites is mainly controlled by the thermal chemical ablation, sublimation of carbon, and mechanical breakage. The formation of needle-shaped fibres and shell-shaped matrices is attributed to both the thermal chemical ablation and sublimation of carbon, while carbon fragments and fractured fibres or matrices result from the mechanical breakage.

A green and natural biomass carbon with hollow structure was first reported derived from waste makeup cotton, which was prepared by facile pyrolysis and carbonisation in the nitrogen-filled vacuum tube furnace. Utilised as lithium-ion batteries (LIBs) anode materials, the hollow structure exhibits superior cycling and rate performance. At the current density of 100 mA g−1, it demonstrates a reversible capacity of 340 mAh g−1 with the Coulombic efficiency of 58.8%, and the reversible capacity gradually increases to 450 mAh g−1 at 300 cycles, displaying long cycling stability. Even at a higher current density of 500 mA g−1, the capacity can be maintained around 245 mAh g−1 after 150 cycles. Moreover, the hollow carbon exhibits excellent rate capability (222 mAh g−1 at an ultrahigh rate of 2000 mA g−1). This enhanced property can be attributed to its special hollow structure, which could provide fast lithium ions and electrons transfer path to facilitate the electrochemical reaction. The authors believe this work could help to design new carbon materials with green and environmental protection as anode materials for LIBs.

Polysulfides (Li2Sx) have become key points that limit capacity improvement of lithium-sulfur batteries because of their high solubility. Oxygen-containing functional groups (such as C–O–H, C–O–C and C O) can effectively relieve a large amount of polysulfide dissolution due to their strong polarity. However, their types and contents on polysulfide-capturing abilities are still unknown. Therefore, three kinds of electrodes containing different contents of hydroxyl (C–O–H), ether (C–O–C) and carbonyl (C O) groups on carbon surface are controlled by changing pyrolysis times of dandelion. Electrochemical performance of lithium-sulfur batteries is tested to analyze influence of these groups on polysulfide-capturing abilities. It is discovered that C O and C–O–H groups can obviously inhibit shuttle effects of polysulfides during their initial production. In addition, a large number of C O bonds are converted to C–O–H bonds. More C–O–H bonds facilitate reversible capture of polysulfides and improve capacities. The introduction of C–O–C groups is not suitable for capturing more polysulfides rapidly and the appearance of ether groups limits conversion process of C–O–H groups. Both S load and discharging/charging process can effectively regulate evolution of three valence bonds, which is conducive to improving rate performance of lithium-sulfur batteries.

We report the in situ generation of NiCoV-LTH (layered triple hydroxide) on nickel foam (NF) for electrocatalytic oxygen evolution reaction (OER). By adjusting the molar ratio of Co/V, the NiCoV-LT...

The hydrophilicity/hydrophobicity of zeolites has been received increasing attentions due to its great influence on the physical, chemical property and application of zeolites. Generally, zeolites ...

The vital challenge of a layered manganese oxide cathode for sodium-ion batteries is its severe capacity degradation and sluggish ion diffusion kinetics caused by irreversible phase transitions. In response to this problem, the spinel-layered manganese-based composite with an intergrowth structure is ingeniously designed by virtue of an interesting spinel-to-layered transformation in the delithiated LiMn2O4 under Na+ insertion. This unique spinel-layered intergrowth structure is strongly confirmed by combining multiple structure analysis techniques. The layered component can provide more reversible capacity, while the spinel component is crucial for the stabilized crystal structure and accelerated ion diffusion kinetics. As an appealing cathode for sodium-ion batteries, the layered-spinel composite delivers a high reversible capacity of 180.9 mAh g-1, excellent cycling stability, and superior rate capability with 55.7 mAh g-1 at 12 C. Furthermore, the reaction mechanism upon Na+ extraction/insertion is revealed in detail by ex situ X-ray diffraction and X-ray photoelectron spectroscopy, indicating that Na+ ions can be accommodated by the layered structure at a low voltage and by the spinel at a high voltage. This study will provide a new idea for the rational design of an advanced cathode for sodium-ion batteries.

Developing the highly active, cost-effective, environmental-friendly, and ultra-stable nonprecious electrocatalysts for hydrogen evolution reaction (HER) is distinctly indispensable for the large-scale practical applications of hydrolytic hydrogen production. Herein, we report the synthesis of well-integrated electrode, NiV layered double hydroxide nanosheet array grown in-situ on porous nickel foam (abbreviated as in-NiV-LDH/NF) via the facile one-step hydrothermal route. Interestingly, the valence configuration of vanadium (V) sites in such NiV-LDH are well dominated by the innovative use of NF as the reducing regulator, achieving the reassembled in-NiV-LDH/NF with a high proportion of trivalent V ions (V3+), and then an enhanced intrinsic electrocatalytic HER activity. The HER testing results show that the in-NiV-LDH/NF drives the current densities of 10 and 100 mA cm−2 at extremely low overpotentials of 114 and 245 mV without iR-compensation respectively, even outperforms commercial 20 wt% Pt/C at the large current density of over 80 mA cm−2 in alkaline media, as well as gives robust catalytic durability of at least 100 h in both alkaline and neutral media. More importantly, this work provides a fresh perspective for designing bimetal (oxy) hydroxides electrocatalysts with efficient hydrogen generation.

Self-assembled cactus-like NH4V3O8 is prepared through polyethylene glycol (PEG)-assisted hydrothermal synthesis method. The samples are characterized by X-ray diffraction and scanning electron microscopy techniques. Adjusting the pH value of the solution can effectively control the morphology of NH4V3O8. The electrochemical measurements indicate that the sample which pH value is 3.7, shows the best cycling performance. It delivers an initial discharge capacity is 228 mAh g−1 and maintains at 156 mAh g−1 under 15 mA g−1 after 50 cycles. The proposed synthetic method can also be developed to address other electrode materials with inferior electronic conductivity and lithium ion diffusion.

The photocatalytic reclamation of the environment requires improved catalysts, as severe charge recombination currently limits their practical application. This study describes a simple synthesis of SnO2−x/Sb2O3 composite by the mechanical milling method. The coupling of SnO2−x possessing oxygen vacancies (OVs) with Sb2O3 is a new approach for obtaining materials with outstanding photocatalytic properties. For the photo-oxidation of isopropanol (IPA) within 5 h, the acetone yield over SnO2−x/Sb2O3 composite with mass ratio of 1:4 was 22.67 and 10.5 times higher than those of SnO2−x and Sb2O3, respectively, and the carbon dioxide output was 13.29 and 7.46 times higher than those of SnO2−x and Sb2O3, respectively. This results showed that the OVs-induced SnO2−x/Sb2O3 heterostructures have a very high IPA photo-oxidation catalytic degradation activity, even after six cycles with no obvious decline. Combination of defect engineering and heterojunction can be a powerful tool for obtaining broad light absorption and high photo-induced charge separation efficiency, which contributes to improving the photocatalytic IPA degradation property.

Developing highly efficient electrocatalysts with hierarchical structures while revealing their electrochemical reaction mechanism is crucial for pushing commercial water splitting application. Her...

A novel (NH4)2Mo4O13/N-doped porous carbon composite is fabricated in situ using a one-step solid technique. Benefiting from the intriguing features of this composite, it undergoes an intercalation and conversion reaction mechanism with diffusion-controlled Li storage behaviour, exhibiting an excellent reversible capacity of 1151 mA h g-1 over 350 cycles.

The construction of nanoporous structure combined with the optimization of electronic structure toward electrocatalysts could be a promising and effective approach to boosting their catalytic performance. Herein, we rationally synthesized a novel Ni3+-doped ultrathin NiZn layered double hydroxide nanomesh supported on nickel foam (Ni(II,III)Zn-LDH/NF-nm) by a facile one-step methanol-assisted hydrothermal method. Results show that methanol can not only trigger the generation of ultrathin nanomesh structure, but adjust portion of Ni2+ to Ni3+ and thus to result in the Ni3+-doped NiZn-LDH nanomesh material. The nanoporous feature endows Ni(II,III)Zn-LDH/NF-nm with abundant exposed catalytic active sites and fast mass transfer for alkaline water electrolysis. More importantly, the Ni3+ doping can facilitate the available formation of highly active NiOOH phase on the surface for the oxygen evolution reaction (OER), accompanied by increased oxygen vacancies that can greatly enhance the electronic conductivity, leading to the improved intrinsic activity and the accelerated electrocatalytic OER reaction kinetics. As expected, the as-prepared Ni(II,III)Zn-LDH/NF-nm has relatively low overpotentials of 320 and 370 mV to drive large current densities of 100 and 500 mA cm−2, respectively, and a small Tafel slope of 63.9 mV dec−1, extremely superior to RuO2/NF and NiZn-LDH/NF-ns counterpart. Meanwhile, the electrolyzer assembled for overall water splitting by Ni(II,III)Zn-LDH/NF-nm yields the outstanding catalytic activity and stability. This work highlights a feasible strategy to design and develop high-efficiency water splitting electrocatalysts via engineering on composition and nanostructure.

Metal–organic frameworks (MOFs) with a high density of metal nodes have great potential in the application of heterogeneous catalysis. However, identifying the real active site in MOF structures and tuning its amount to further improve its catalytic performance are still a great challenge. In this paper, defective UiO-66 modulated with trifluoroacetic acid (TFA) was synthesized and used for the conversion of cyclohexanone to cyclohexanol via hydrogen transfer. We found that not all structural defects were responsible for catalytic reaction, and only structural defects where open metal sites are created by a modulator were effective for cyclohexanone conversion. Then we successfully tuned the number of each type of effective structural defect (that is, missing-cluster defects or missing-linker defects) in modulated UiO-66 via precise control of the synthetic/treatment conditions. Our experimental results showed that the creation of both types of structural defects can increase the amount of effective open metal sites and then enhance their catalytic performances under the same conditions. Furthermore, the mechanism study confirmed that this reaction indeed proceeded on effective open metal sites. Our findings have further deepened the understanding of the roles of structural defects in MOF heterogeneous catalysis.

Polymeric membranes with high ionic conductivity and solvent molecule blocking capability are attracting considerable attention as separators for new-generation batteries adopting hybrid electrolytes. The performances of the membranes are closely dependent on their microstructures and functional groups. Here, we report the design and fabrication of a carboxyl-functionalized polymer-of-intrinsic-microporosity (PIM) membrane, which has optimal surface properties and microporous channels (∼0.8 nm) to permit cation (Li+ or Na+) transportation, while preventing solvent molecule penetration. Using a droplet-templating strategy, we create large pores on both surfaces of the PIM-membrane to improve its interfacial contact with electrolytes. The obtained membrane integrates good mechanical strength with high thermal and electrochemical stability, demonstrating a great potential for battery applications as a flexible separator. When intercalated with Li+, the membrane (PIM-1-COOLi) exhibits a remarkable Li+ conductivity in both aqueous (6.5 × 10−3 S cm−1) and organic (7.3 × 10−4 S cm−1) solutions, as well as a good solvent permeation resistance (19 μmol cm−2 min−1 at 10 Pa for H2O). Taking these advantages of the PIM-membrane, we are able to fabricate challenging batteries with hybrid electrolytes, such as Li–H2O2 and Na–H2O2 batteries (Li/Na anode with organic electrolyte and H2O2 cathode with aqueous electrolyte), into a flexible laminated form. The as-fabricated battery shows an excellent discharge performance, comparable to a model battery constructed with the commercial ceramic Li super-ionic conductor, but is more tolerant to mechanical treatment and harsh environment. Our study demonstrates that PIM represents a promising platform for developing flexible secondary batteries with hybrid electrolytes, which are particularly desirable for wearable and portable electronic devices.

Photocatalytic degradation of organic pollutants in wastewater is one of the most promising strategies for environmental remediation, and photocatalysts as the prerequisite have received considerable attention. Herein we reported highly efficient, nontoxic, and inexpensive Mg0.8Zn0.2O microspheres with a diameter of around 36 μm prepared through reaction between CO32−, Mg2+ and Zn2+ for degrading organic dyes. The molar ratio between Mg2+ and Zn2+ was found to play a crucial role in determining the morphology and photocatalytic performance of the resulting product. According to time-dependent experiments, the plausible formation mechanism for the spherical-like Mg0.8Zn0.2O composite was proposed, in which irregular agglomerates composed of fine powders were first formed followed by their transformation into rod-like structures. Due to their thermal instability, the rod-like particles underwent further self-assembly and became a more stable spherical-like product with ZnCO3 embedded in the space between Mg5(CO3)4(OH)2·4H2O sheets. After investigating the photocatalytic performance, the results demonstrated that the developed Mg0.8Zn0.2O composite was not only superior to other state-of-the-art catalysts such as P25 TiO2 and g-C3N4 in degrading organic dyes upon irradiation under either UV light or visible light, but also was an amphoteric photocatalyst more favorable for degrading organic dyes in both strongly acidic (pH 2–4) and strongly alkaline (pH 12) solutions. Moreover, its catalytic efficiency remained as high as 98.3% after six cycles. These features made the developed Mg0.8Zn0.2O composite promising in practical utilization for treatment of organic dyes. Further experiments including photoluminescence, adsorption and photoelectrochemical measurements accounted for the underlying photocatalytic mechanism of the Mg0.8Zn0.2O composite for degradation of organic dyes.

Pulverization is a common phenomenon of alloy-based anode materials during the sodiation/desodiation process and usually leads to sluggish Na+ insertion/extraction kinetics. Although many studies have reported how to avoid or inhibit the occurrence of this phenomenon, it is still a great challenge in the research on alloy-based anode materials. Herein, we have achieved fast Na+ extraction in an Sb2Se3 alloy anode by constructing uniform carbon capsule confined Sb2Se3 composites (SSCs). Further analysis results indicate that the fast Na+ extraction is attributed to the uniform carbon capsule confined Sb2Se3 structure. In this structure, the carbon capsule can suppress the huge volume change of Sb2Se3 during the Na+ insertion process and uniformly release stress during the Na+ extraction process, maintaining the stable electrode structure. Specifically, Sb2Se3 is in situ pulverized in the intact carbon capsule and maintains the original rod-like outline, which provides a stable and short Na+ extraction pathway, good electrical contact, and a stable SEI layer on the surface of the intact carbon capsule and inhibits the side reaction of Sb2Se3. Therefore, the SSC exhibits fast Na+ extraction with a high reversible capacity of 324 mA h g−1 at 5 A g−1. The capacity is still as high as 380 mA h g−1 after 600 cycles at 2 A g−1.

Formic acid (HCOOH), the acidic form of formate, is an important hydrogen carrier which can be directly used in fuel cells. Development of earth-abundant element-based catalysts to convert carbon dioxide (CO2) into HCOOH or formate with high selectivity and high efficiency has been a vigorous research activity in recent years but remains an unsolved challenge. In this contribution, using one-step anodization, we prepare nanotubular SnO2 porous nanostructures with high surface area (90.1 m2 g−1), large porosity (0.74 cm3 g−1), and rich grain boundaries for electrochemical CO2 reduction (CO2RR). They exhibit stable 95% faradaic efficiency (FE) towards CO2RR and 73% FE for formate at −0.8 VRHE. The notable performance of such SnO2 nanostructures can be attributed to their unique structural and chemical properties, which provide active sites for CO2 adsorption and conversion, and easy access for CO2 to the active sites. The insights gained from the structure/property relationships might be beneficial for designing superior electrocatalysts for CO2 electroreduction into formate.

A Sn2Nb2O7–Super P nanocomposite (SNO–SP) as an anode material for lithium ion batteries is successfully synthesized through a simple hydrothermal method. In the SNO–SP nanocomposite, SNO nanocrystals are homogeneously anchored on the surface of Super P carbon spheres, and there is the Sn–C bond between SNO and Super P. Research into the electrochemical performance shows that the Sn–C bond can provide a short pathway for fast electron transport during the charge–discharge process and effectively accelerate the electronic and ionic diffusion kinetics, which is advantageous for the improvement of the electrochemical performance. The SNO–SP electrode exhibits a relatively high reversible capacity (616.7 mA h g−1 at 0.1 A g−1 after 100 cycles) and outstanding high-rate capability (224.4 mA h g−1 even at 2.0 A g−1).

Bridging S22− moieties have been demonstrated to be highly active sites existing in metal polysulfides for the hydrogen evolution reaction (HER), thus the incorporation of high-density bridging S22− into a Ni3S2 material to improve its electrocatalytic HER performance is highly desirable and challenging. Herein, we report a novel Ni3S2 nanorod array decorated with (020)-oriented VS4 nanocrystals grown on nickel foam (Shig-NS-rod/NF) via a simple and facile solvothermal method. Results show that the in situ incorporation of VS4 not only triggers the formation of such a nanorod array structure, but also contributes to the uniform grafting of high-density and high catalytically active bridging S22− sites on the interface between Ni3S2 and VS4 for enhanced HER activity, and also promotes the absorption ability of OH− radicals and thus accelerates the HER Volmer step in alkaline media. As expected, the resultant Shig-NS-rod/NF material exhibits impressive catalytic performance toward the HER, with a much lower overpotential of 137 mV at 10 mA cm−2 and a long-term durability for at least 22 h, and is superior to Ni3S2 nanorod arrays with low-density bridging S22− (Slow-NS-rod/NF) and NS-film/NF counterparts (without VS4), even outperforming the NF-supported 20% Pt/C at a large current density of over 120 mA cm−2. Our findings put forward fresh insight into the rational design of highly efficient electrocatalysts toward the HER for green hydrogen fuel production.

The rational design and development of cost-effective and high-efficiency bifunctional electrocatalysts for overall water splitting is of prime significance for advancing large-scale commercial hydrogen production. Herein, a novel nanoporous NiAl layered double hydroxide nanosheet array with optimized Ni active sites on nickel foam (np-NiAl-LDH/NF) is prepared by a facile and simple metal-defect engineering strategy. We demonstrate that the partial leaking of catalytically inactive Al sites in NiAl-LDH nanosheets during anodic electrochemical etching can not only trigger the generation of a nanoporous structure and electron-rich Ni2+ sites, but can also increase the content of Ni3+ active sites accompanied by abundant oxygen defects, resulting in the synchronously increased density and intrinsic activity of Ni active sites and also enhanced mass and electron transport, thus greatly promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. As expected, the as-obtained np-NiAl-LDH/NF electrode needs extremely small overpotentials of 90 and 180 mV to deliver the 10 mA cm−2 current density for the HER and OER in alkaline media, respectively. Moreover, an alkaline electrolyzer assembled with np-NiAl-LDH/NF functioning as both the anode and cathode can yield 10 and 100 mA cm−2 at quite low voltages of ∼1.5 and 1.7 V, respectively, far outperforming the Pt/C/NF–IrO2/NF-coupled electrolyzer, and can give durable stability for at least 60 h. This work provides new insights for creating highly efficient Ni-based electrocatalysts toward overall water splitting via engineering on catalytically active Ni sites.

Design and fabrication of bifunctional efficient and durable noble-metal-free electrocatalyst for hydrogen and oxygen evolution is highly desirable and challenging for overall water splitting. Herein, a novel hybrid nanostructure with Ni2P/CoP nanoparticles decorated on a porous N-doped fullerene nanorod (p-NFNR@Ni-Co-P) was developed as a bifunctional electrocatalyst. Benefiting from the electric current collector (ECC) effect of FNR for the active Ni2P/CoP nanoparticles, the p-NFNR@Ni-Co-P exhibited outstanding electrocatalytic performance for overall water splitting in alkaline medium. To deliver a current density of 10 mA cm-2, the electrolytic cell assembled by p-NFNR@Ni-Co-P merely required a potential as low as 1.62 V, superior to the benchmark noble-metal-based electrocatalyst. Experimental and theoretical results demonstrated that the surface engineered FNR serving as an ECC played a critical role in accelerating the charge transfer during the electrocatalytic reaction. The present work paves the way for fullerene nanostructures in the realm of energy conversion and storage.

Developing 3 D self-assembled nanoarchitectures with well-defined crystal structures is an effective strategy to enhance the electrochemical performances of electrode materials. (1 1 0)-oriented and bridged-nanoblocks self-assembled VS4 microspheres are controllably synthesized by a facile one-step hydrothermal method. The (1 1 0)-bridged structure sets up open pathways for Na+ diffusion among nanoblocks, and the (1 1 0)-oriented structure provides unobstructed pathways for Na+ diffusion in the nanoblocks, which collectively constructs multidimensional Na+ transfer channels in the VS4 microspheres, promoting the electrochemical kinetics. As an anode for Na-ion batteries (SIBs), this material exhibits pseudocapacitive Na+ storage and excellent rate capability, delivering high capacities of 339 and 270 mAh g-1 at rates of 0.1 and 2.0 A g-1 , respectively, with a capacity retention of 79 % in the voltage window of 0.5-3.0 V. In particular, the reversible capacity reaches 575 mAh g-1 after 300 cycles even at 1.0 A g-1 in the voltage window of 0.05-3.0 V, outperforming those of the ever-reported VS4 -based anode materials. This work presents an effective strategy to the exploration and design of high-performance anodes for SIBs.

Microparticles with carbon microsphere (CMS) cores and poly(methyl methacrylate) (PMMA) shells were successfully synthesized through an aqueous-phase radical polymerization method. The morphologies...

Building Chemical bonds is an effective strategy to obtain excellent performance of electrode materials. Herein, we report SnSe nanoparticles growth on carbon nanotubes (SnSe-CNTs) composite with strong Sn C bonding for high performance LIBs anode. The composite electrode exhibits high reversible capacity of 772 mAh g−1 after 200 cycles at a current density of 200 mA g−1. Even under higher current density of 1 A g−1, the capacity of composite electrode still maintains 323 mAh g−1 after 1000 cycles, the capacity retention rate is as high as 69.5%. It is found that strong electronic coupling between SnSe nanoparticles and carbon nanotubes conducive to the rapid transmission of electron/ion, facilitating the reversible conversion reaction between Sn and Li2Se to form SnSe. Meanwhile, Sn C bonding significantly improved structural stability of SnSe nanoparticles growth on carbon nanotubes composites electrode. These encouraging results of chemical bonding provide new opportunities for designing advanced electrode materials.

Transition oxides are a kind of promising anode materials for lithium-ion batteries due to their high capacity and low cost. However, it is a great challenge to realize high power density and long cycle life. Size control and surface coating are effective ways to increase reaction sites and improve electrical conductivity. In this work, rice crust-like structure of thin carbon layer coated Fe3O4 nanoparticles (∼15 nm) uniformly covering rGO sheets (Fe3O4@C/rGO) is achieved. This composite delivers a high capacity of 594 mAh g−1 even after 1000 cycles at a high current rate of 5.0 A g−1, which can be attributed to the high surface pseudocapacitance dominated storage mechanism. Further analysis reveals that the high extrinsic pseudocapacitance is closed to the nanosized structure and carbon coating, because large surface area and good electrical conductivity are essential for the improvement of extrinsic pseudocapacitance. This work offers a new perspective for future structure design for high-rate and long-life anode materials of lithium-ion batteries.

Nanorod assembled three-dimensional (3D) hierarchical Zn0.2Cd0.8S microspheres were successfully prepared by a facile one-pot microwave hydrothermal approach using ethylenediamine (EN) as a template agent. The optimal 3D hierarchical Zn0.2Cd0.8S microspheres (ZCS-30) is obtained when adding 30 mL into the synthetic system, which can function as a highly active photocatalyst for H2 evolution under visible-light irradiation with the wavelength of 420 nm, delivering an activity approximately 2.5 and 7.5 times higher than that of Zn0.2Cd0.8S nanoparticles and CdS counterparts, respectively, and giving an apparent quantum efficiency (AQE) of 7.4%. Furthermore, the ZCS-30 photocatalyst shows the good stability after the catalytic H2 evolution for 15 h (5 cycles). In addition, the ZCS-30 photocatalyst exhibits the excellent degradation of Rhodamine B (Rh B) almost up to 80% under the visible light irradiation over a period of 150 min. The results demonstrate that ZCS-30 can serve as a promising visible-light-driven bifunctional photocatalyst for water splitting and dye degradation.

Oxygen-containing functional groups and pseudographic structure are key factors that affect the electrochemical properties of biomass derived carbon materials. In this work, the shaddock peel derived hard carbon with abundant carbon-oxygen double bond (C O) and highly ordered pseudographic structure is successfully synthesized by a H2SO4-assisted hydrothermal pretreatment and subsequent KOH-assisted low temperature (600 °C) pyrolysis procedure. The resulting unique structure is beneficial for the co-effective enhancement of Na+ storage sites and electrochemical reaction kinetics. The hard carbon exhibits excellent cycling and rate performances in sodium-ion batteries, delivering a high reversible capacity of 380 mAhg−1 at 50 mAg−1 after 500 cycles, and that of 274 and 199 mAhg−1 even at 500 and 1000 mAg−1, respectively. This performance is superior to the previously reported shaddock peel derived hard carbons. Besides, the surface-controlled redox mechanism of C O and Na+ occurring at the hard carbon is clearly revealed.