Erratum to: Effects of redox-active interlayer anions on the oxygen evolution reactivity of NiFe-layered double hydroxide nanosheets

Nano Research - The labels in Fig. 8 in the original version of this article were unfortunately misplaced. The corrected figure is as follow.     

不同阴离子插层的ZnMgAl层状双氢氧化物对聚氨酯弹性体阻燃抑烟性能的影响

分别以水热法及离子交换法制备了NO_3~-和Mo_7O_(24)~(6-)插层的ZnMgAl三元层状双氢氧化物(NO_3-ZnMgAl LDHs,Mo-ZnMgAl LDHs),并分别将制得的两种LDHs添加到聚氨酯弹性体(PUE)中,研究了不同阴离子插层的LDHs对PUE阻燃抑烟性能的影响。锥形量热仪和烟密度仪研究表明,纯PUE的热释放速率峰值(PHRR)及最大烟密度值(Ds,max)分别为920kW/m~2和452,当NO3-ZnMgAl LDHs、Mo-ZnMgAl LDHs的质量分数为7wt%时,LDHs/PUE复合材料的PHRR和Ds,max分别降低至377kW/m~2、343kW/m~2和216、190,两种LDHs对PUE均有较好的阻燃抑烟效果,Mo-ZnMgAl LDHs的效果更显著。LDHs/PUE复合材料的TGA、残炭的拉曼光谱和XPS研究证实,两种LDHs的加入都能够促进LDHs/PUE复合材料催化成炭,提高残炭率,并且能够提高炭层的石墨化程度,使炭层的抗热氧化能力增强;另外,与NO3-ZnMgAl LDHs相比,Mo-ZnMgAl LDHs的引入能够使Mo-ZnMgAl LDHs/PUE复合材料残炭率和炭层的石墨化程度更高,抗热氧化能力更强,有效地保护基体材料避免受热辐射,隔绝氧气,抑制可燃性气体的挥发。     

A highly active oxygen evolution electrocatalyst: Ultrathin CoNi double hydroxide/CoO nanosheets synthesized via interface-directed assembly

A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide (LDH) and small CoO nanocrystals were designed and synthesized via in situ reduction and interfacedirected assembly in air. The formation of CoNi LDH/CoO nanosheets was attributed to the strong extrusion of hydrated metal–oxide clusters driven by the interfacial tension. The obtained loose and porous nanosheets exhibited low crystallinity due to the presence of numerous defects. Owing to the orbital hybridization between metal 3d and O 2p orbitals, and electron transfer between metal atoms through Ni–O–Co, a number of Co and Ni atoms in the CoNi LDH present a high +3 valency. These unique characteristics result in a high density of oxygen evolution reaction (OER) active sites, improving the affinity between OH^– and catalyst, and resulting in a large accessible surface area and permeable channels for ion adsorption and transport. Therefore, the resulting nanosheets exhibited high catalytic activity towards the OER. The CoNi LDH/CoO featured a low onset potential of 1.48 V in alkaline medium, and required an overpotential of only 300 mV at a current density of 10 mA·cm^–2, while displaying good stability in accelerated durability tests.

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Fast formation of single-unit-cell-thick and defect-rich layered double hydroxide nanosheets with highly enhanced oxygen evolution reaction for water splitting

The development of high-efficiency electrocatalysts for oxygen evolution reactions (OERs) plays an important role in the water-splitting process. Herein, we report a facile way to obtain two-dimensional (2D) single-unit-cell-thick layered double hydroxide (LDH) nanosheets (NSs, ～1.3 nm) within only 5 min. These nanosheets presented significantly enhanced OER performance compared to bulk LDH systems fabricated using the conventional co-precipitation method. The current strategy further allowed control over the chemical compositions and electrochemical activities of the LDH NSs. For example, CoFe-LDH NSs presented the lowest overpotential of 0.28 V at 10 mA/cm², and the NiFe-LDHs NSs showed Tafel slopes of 33.4 mV/decade and nearly 100% faradaic efficiency, thus outperforming state-of-the-art IrO₂ water electrolysis catalysts. Moreover, positron annihilation lifetime spectroscopy and high-resolution transmission electron microscopy observations confirmed that rich defects and distorted lattices occurred within the 2D LDH NSs, which could supply abundant electrochemically active OER sites. Periodic calculations based on density functional theory (DFT) further showed that the CoFe- and NiFe-LDHs presented very low energy gaps and obvious spin-polarization behavior, which facilitated high electron mobility during the OER process. Therefore, this work presents a combined experimental and theoretical study on 2D single-unit-cell-thick LDH NSs with high OER activities, which have potential application in water splitting for renewable energy.

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Strengthen metal-oxygen covalency of CoFe-layered double hydroxide for efficient mild oxygen evolution

Oxygen evolution reaction(OER)is crucial for hydrogen production as well as other energy storage technologies.CoFe-layered double hydroxide(CoFe-OH)has been widely considered as one of the most efficient electrocatalysts for OER in basic aqueous solution.However,it still suffers from low activity in neutral electrolyte.This paper describes partially oxidized CoFe-OH(PO-CoFe-OH)with enhanced covalency of M-O bonds and displays enhanced OER performance under mild condition.Mechanism studies reveal the suitably enhanced M-O covalency in PO-CoFe-OH shifts the OER mechanism to lattice oxygen oxidation mechanism and also promotes the rate-limiting deprotonation,providing superior OER performance.It just requires the overpotentials of 186 and 365 mV to drive the current density densities of 1 and 10 mA·cm^-2 in 0.1 M KHCO₃ aqueous solution(pH=8.3),respectively.It provides a new process for rational design of efficient catalysts for water oxidation in mild conditions.     

Fabrication of NiFe layered double hydroxide with well-defined laminar superstructure as highly efficient oxygen evolution electrocatalysts

Structure–activity relationship (SAR) is the key problem of nanoscience, thus to fabricate novel and well-defined nanostructure will provide a new insight on catalyst preparation method. Highly active and low cost electrocatalysts for oxygen evolution reaction (OER) are of great importance for future renewable energy conversion and storage. Herein, NiFe-based layered double hydroxides with laminar structure (NFLS) were successfully fabricated via a one-step hydrothermal approach by using sodium dodecyl sulfate as surfactant. The as-fabricated NFLS showed a well-defined periodic layered-stacking geometry with a scale down to 1-nm. Benefitting from the unique structure, NFLS exhibited an excellent catalytic activity towards OER with current densities of 10 mA·cm⁻² at overpotential of 197 mV. The synergistic effect of Ni and Fe plays a key role in electrode reactions. The present work provides a new insight to improve the OER performance by rational design of electrocatalysts with unique structures.

     

Co-vacancy-rich Co1-xS nanosheets anchored on rGO for high-efficiency oxygen evolution

Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water.Engineering favorable defects on the electrocatalysts to provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics.Herein,Col-xS nanosheets were designed and grown on reduced graphene oxide (rGO) by controlling the successive two-step hydrothermal reaction.A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO,which were then sulfurized into Col-xS by L-cysteine at a higher hydrothermal temperature.Because of the non-stoichiometric defects and ultrathin sheet-like structure,additional cobalt vacancies (V'Co) were formed/exposed on the catalyst surface,which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte.The resulting Col-xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm-2 in an alkaline electrolyte for the oxygen evolution reaction (OER).Density functional theory calculations indicated that the V'Co on the Col-xS/rGO hybrid functioned as catalytic sites for enhanced OER.They also reduced the energy barrier for the transformation of intermediate oxygenated species,promoting the OER thermodynamics.     

氧空位超薄Co2AlO4纳米片的合成及其增强电催化氧析出反应（英文）

本文报道了通过脱合金和后续退火工艺合成一种新型超薄二维尖晶石结构的Co2Al O4纳米片.通过温和的溶剂热还原法将氧空位缺陷引入Co2Al O4纳米片中,使得电化学表面积增大,活性位密度变高,钴原子得到电子而产生更多的空轨道.这些空轨道有利于接受水分子中氧原子的孤对电子,促进水分子的活化.含有氧空位的超薄Co2Al O4纳米片在10 m A cm^-2时的过电位为280 m V,塔菲尔斜率为70.98 m V dec^-1.此外,其在碱性溶液中也表现出显著的稳定性,并且优于多数已报道的Co3O4电催化剂.该工作为制备高效的可持续新能源材料提供了新思路.     

Effect of interlayer anions on the physicochemical properties of zinc–aluminium hydrotalcite-like compounds

Zinc–aluminium hydrotalcite-like compounds (ZnAlAn-–HT) with a Zn/Al atomic ratio 2.0 and An- = CO2-3, Cl-, NO-3 and SO2-4, were synthesized by coprecipitation under low supersaturation. Their physicochemical properties were studied using powder X-ray diffraction (PXRD), infrared (IR) and laser Raman (LR) spectra, thermogravimetry (TG), differential scanning calorimetry (DSC), evolved gas analysis (EGA), 27Al MAS NMR, BET surface area and pore-size determination. The PXRD of the synthesized samples showed that the crystallinity was affected by the nature of the anions present in the interlayer space. The IR and LR studies revealed that except the NO-3 ion, the symmetry of these interlayer anions was reduced upon intercalation. The TG, DSC and EGA results showed two or three stages of weight loss corresponding to the removal of the interlayer water, structural water and the anion, respectively. The activation energy, Ea, for the decomposition process was found to decrease in the order ZnAlCO3–HT>ZnAlSO4–HT>ZnAlCl–HT>ZnAlNO3–HT. Formation of a pentacoordinated Al (AlV) in addition to the octahedral (AlVI) and tetrahedral Al (AlIV) was the special feature noticed in the 27Al MAS NMR of the calcined samples. Thermal calcination around 500 °C resulted in the formation of non-stoichiometric ZnO whose crystallinity decreased in the order ZnAlNO3–CHT>ZnAlCl–CHT>ZnAlSO4–CHT>ZnAlCO3–HT while their extent of solid solubility was found to be the reverse. The crystallinity of the calcined samples was also correlated with surface area and pore-size determination. This revised version was published online in November 2006 with corrections to the Cover Date.     

Comparison of the fluoride,arsenate and nitrate anions water depollution potential of a calcined quintinite,a layered double hydroxide compound

The potential for removing anionic pollutants such as F⁻, HAsO₄²⁻, and NO₃⁻ from water by mixed oxides issued from the moderate thermal treatment of quintinite (Mg₄Al₂ LDH) has been studied. This compound shows good trapping properties for F⁻ and HAsO₄²⁻, and a low potential for NO₃⁻, due to the competition with OH⁻. The competition between these three anions and CO₃²⁻ has been envisaged and shows that CO₃²⁻ is able to easily replace F⁻ and NO₃⁻, making the mixed oxides issued from MgAl LDH an inappropriate trap for F⁻ and NO₃⁻. However, only small amounts of arsenic are released after the CO₃²⁻ introduction in water. Moreover, arsenates are able to replace carbonates even at lower concentrations. This means that HAsO₄²⁻ anions present a stronger affinity than CO₃²⁻ for the LDH structure. This makes mixed oxides issued from MgAl LDH very promising materials for the removal of arsenic in polluted waters.     

Layered double hydroxide using hydrothermal treatment: morphology evolution,intercalation and release kinetics of diclofenac sodium

The present work demonstrates the possibilities of hydrothermal transformation of Zn-Al layered double hydroxide (LDH) nanostructure by varying the synthetic conditions. The manipulation in washing step before hydrothermal treatment allows control over crystal morphologies, size and stability of their aqueous solutions. We examined the crystal growth process in the presence and the absence of extra ions during hydrothermal treatment and its dependence on the drug (diclofenac sodium (Dic-Na)) loading and release processes. Hexagonal plate-like crystals show sustained release with ～90% of the drug from the matrix in a week, suggesting the applicability of LDH nanohybrids in sustained drug delivery systems. The fits to the release kinetics data indicated the drug release as a diffusion-controlled release process. LDH with rod-like morphology shows excellent colloidal stability in aqueous suspension, as studied by photon correlation spectroscopy.     

Layered double hydroxide as nanofiller in the development of polyurethane nanocomposites

Polyurethane (PU)/Dodecyl sulphate intercalated layered double hydroxide (DS-LDH) nanocomposites were successfully synthesized from PU prepolymer and polyol TG (mixtures of glycerol and trimethylolpropane) for the first time. Formation of partially exfoliated structures of PU/DS-LDH nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Analysis of tensile properties showed significant improvements in tensile strength (TS) and elongation at break (EB) of about 407% and 83% for PU/DS-LDH (3 wt%) nanocomposite. The observed excellent concurrent improvement in TS and EB is attributed to the relatively better reinforcing effect of partially exfoliated DS-LDH layers in PU making the present investigation most noteworthy. In addition, gradual improvement in thermal stability and limiting oxygen index (LOI) with increasing DS-LDH loading makes these nanocomposites versatile and hence suitable for many critical applications.     

Effects of Ag interlayer on the optoelectrical properties of TiON films

A sandwich structure of TiON/Ag/TiON (TAgT) multilayer films was prepared onto glass substrates using RF and DC magnetron sputtering without intentional substrate heating. The thicknesses of each layer in the TAgT films were set at 50 nm, 5 nm and 45 nm. The optoelectrical properties of the TiON films were strongly influenced by the presence of an Ag interlayer. Although the optical transmittance of the film deteriorated when an Ag interlayer was added, the films had a low resistivity of 9.0 × 10⁻⁴ Ω cm due to increased carrier density. In addition, the TAgT films show work functions of 4.4 eV, which are suitable for organic light emitting diode (OLED) applications.The experimental results indicate that TiON film manufactured with a 5-nm thick Ag interlayer is an attractive candidate for use as a transparent electrode in large area electronic applications such as solar cells and displays.     

层间阳离子对蒙脱石凝胶性能的影响

以4种不同产地的蒙脱石原矿为原料,制备不同价态6种金属层间阳离子的蒙脱石及其悬浮液,研究层间阳离子对蒙脱石的结构、形貌、Zeta电位、分散状态和凝胶性能的影响,以及各影响因素之间的关系。结果表明:蒙脱石原料产地对蒙脱石凝胶性能的影响不大;低价态层间阳离子的蒙脱石的水合离子半径较大,Zeta电位值高,悬浮液的分散性越好,黏度值大,凝胶性能好;对于同价态的阳离子的蒙脱石,其水合离子半径越大,凝胶性能越好。     

Effects of SiNx interlayer on characterisation of amorphous diamond-like carbon films

The magnetron sputtering amorphous diamond-like carbon film is successfully deposited by SiN_x interlayer approach. The scanning electron microscopy study reveals the creation of high uniform surface micrograph diamond-like carbon films with SiN_x interlayer. For comparison, diamond-like carbon films with different interlayers are also grown. The Raman spectra are analyzed in order to characterize the stressed induce peak shifts of the films. The interactions of C atom with Si(100) and SiN_x surface are studied by density functional theory simulation. The effects of interlayers on the films deposition and the considering deposition mechanism are discussed. It is suggested that the diamond-like carbon and SiN_x bilayer structure can help to render applications in protective coatings and high quality silicon on diamond related radiation tolerance devices.