Novel preparation of high activity 1T-phase MoS2 ultra-thin flakes by layered double hydroxide for enhanced hydrogen evolution performance

In this study, 1T phase molybdenum disulfide Ultra-thin Flakes (1T-MoS₂ UFs) with high HER activity was successfully prepared by spatial confinement of layered double hydroxides (LDHs). The growth of MoS₂ tends to be thin layer and high 1T phase due to the binding force of LDHs, this novel strategy is different from other phase transition methods, like alkali metal ion intercalation, electron irradiation, and stress induction, etc. The 1T-MoS₂ UFs were used as hydrogen evolution reaction (HER) catalysts, when current density is 10 mA/cm², the potential (vs. RHE) is 254 mV and the Tafel slope is only 64 mV/dec under the optimal condition. The superior HER activity is due to highly active 1T phase and rich defects.     

低温共沉淀法合成多孔CoFe LDH纳米片电催化剂

通过低温共沉淀技术合成了多孔CoFe层状双金属氢氧化物（CoFe LDH）纳米片。运用X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电镜（SEM）、透射电镜（TEM）等手段对产物的物相、组成及微观形貌进行了表征,并探讨了铁离子（Fe³⁺）含量对CoFe LDH纳米结构生长行为的影响,考察了制备的产物作为电催化剂在电解水析氧反应中的性能。结果表明,Fe³⁺的加入可以有效调节产物的形貌、结晶度和孔道结构。在合适的Co与Fe比例条件下,制备的CoFe LDH可形成多孔纳米片,且增大了总孔体积,增加了表面活性位点。同时,结晶CoFe LDH纳米片可促进Co和Fe离子间的电荷转移行为,从而提高产物的电催化活性。对于电解水析氧反应,当电流密度为10 mA/cm²时,结晶Co_0.67Fe_0.33 LDH多孔纳米片所需的过电势仅为291 mV,Tafel斜率为33 mV/dec,并展现出良好的循环稳定性。     

层状氢氧化镁铝的改性与成型及其对PO43-的吸附脱除性能

利用大型工业设备制备出性能稳定的粉末层状氢氧化镁铝(500kg/批,记为Mg-Al LDH),利用沉积法将Mg-Al LDH进行改性与成型,并对其进行材料表征,探索了Mg-Al LDH的改性机理,研究了改性与成型层状氢氧化镁铝(记为MG Mg-Al CLDH)对PO43-的动态吸附脱除及再生性能。结果表明,Mg-AlLDH经改性与成型后,比表面积为233.34m2/g,比未改性时提高了40%,Mg-Al LDH的改性主要是通过氢键键合和离子交换实现的。MG Mg-Al CLDH对PO43-的穿透吸附量是13.49mg/g,是未改性时的6倍以上,再生率为126.24%,MG Mg-Al CLDH吸附脱除PO43-后能够满足污水综合排放一级标准0.5mg/L。解决了Mg-Al LDH在实际应用中存在粉末易堵塞床体、无法实现固液分离和再生的问题,同时为水体中磷的脱除提供了一条新型可行之路。     

Chitosan/Poly(Vinyl Alcohol)/LDH Biocomposites With pH-Sensitive Properties

The viscometric parameters of chitosan/poly(vinyl alcohol) mixtures determined at 37°C are sensitive to polymer composition and pH changes, giving information about interpolymer complexes formation. Hybrid composites based on interpolymeric chitosan/poly(vinyl alcohol) complexes and the inorganic matrix of layered double hydroxides were synthesized in the presence of glutaraldehyde. The viscoelastic parameters showed a stronger network formation at pH = 5.5 which is not broken down by the mechanical shear forces. The swelling kinetics of hybrid hydrogels is pH sensitive and the type of diffusion of small molecules into the network was established.     

Polymorphism and spherulite morphology of poly(1,4‐butylene adipate)/organically‐modified layered double hydroxide nanocomposites

A novel biodegradable poly(1,4‐butylene adipate)/organically‐modified layered double hydroxide (PBA/m‐LDH) nanocomposites are synthesized using the solution mixing process. The m‐LDH is originally prepared with magnesium nitrate hexahydrote (Mg(NO₃)₂ 6H₂O), aluminum nitrate‐9‐hydrate (Al(NO₃)₃ 9H₂O), oleic acid, and sorbitol by a novel one‐step co‐precipitation method to intercalate the organo‐modifier of oleic acid and sorbitol into the interlayer of LDH. The structure and morphology of the PBA/m‐LDH nanocomposites are characterized using X‐ray diffraction and transmission electron microscopy (TEM). It has been shown that the m‐LDH is exfoliated and well distributed in PBA matrix. The effect of m‐LDH on the polymorphic crystal and morphology of PBA at various crystallization temperatures (T_cs) would be investigated using WAXD and POM. Both data indicate that the addition of m‐LDH can change the starting formation temperature of α‐form crystals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42526.     

水热反应温度对LA103Z镁锂合金表面MAO/LDH复合膜层微观组织及耐蚀性的影响

目的 研究层状双金属氢氧化物(LDH)形成的水热反应机理,以及水热反应温度对LA103Z镁锂合金表面MAO/LDH复合膜层微观组织及耐蚀性的影响.方法 保持水热反应时间为18 h,改变水热反应温度,在微弧氧化陶瓷层(MAO)表面制备LDH膜层.将制得的Mg-Al LDH/MAO复合膜层置于3.5％NaCl溶液中,进行浸泡和析氢实验,使用XRD、SEM、EDS等测试手段对腐蚀前后的膜层进行表征.结果 不同水热反应温度下,均能在MAO陶瓷层表面形成细小针状结构,经XRD分析得到了LDH的特征衍射峰.在80、90、100℃条件下制备的LDH膜层,表面均匀,截面结构致密,而在120℃条件下制备的LDH膜层,表面针状组织尺寸更为粗大,分布更为密集,但截面蓬松.析氢实验中,在不同水热反应温度下,膜层析氢曲线的斜率由小到大依次为:80℃≈90℃<100℃<120℃LDH膜层在浸泡8 d后,析氢量不足50 mL,远低于120℃条件下制备的膜层(析氢量为150 mL).结论 水热反应过程中,首先在MAO陶瓷层表面形成Mg(OH)2,随后溶液中的Al3+取代部分Mg(OH)2中的Mg2+,形成LDH,最终生长成LDH膜层.在一定温度范围内,随制备温度的降低,Mg-Al LDH/MAO复合膜层的耐蚀性能逐渐增强,这与其表面及截面的微观结构密切相关.     

Preparation and properties of exfoliated nanocomposites through intercalated a photoinitiator into LDH interlayer used for UV curing coatings

The exfoliated polymer/layered double hydroxide (LDH) nanocomposites based on MgAl were prepared through intercalating a photoinitiator into LDH interlayer, following by UV irradiation induced polymerization. The fragmental photoinitiator, 2-hydroxy-2-methyl-1-phenylpropane-1-one (1173) firstly reacted with isophorone diisocyanate (IPDI) to obtain the semiadduct, 1173-IPDI, and then reacted with the LDH modified by aminoundecanoic acid, obtaining LDH-1173 with an intercalated microstructure, which was characterized by FTIR, XRD, and TGA measurements. The obtained LDH-1173 was mixed with the multifunctional acrylate oligomer and monomer, and then exposed to a UV lamp to prepare a polymer/LDH nanocomposite. From the XRD, TEM and HR-TEM analysis, as well the photopolymerization kinetics investigation, it was found that the LDH-1173 effectively initiated the photopolymerization of acrylates, and formed exfoliated polymer/LDH nanocomposites. However, the mostly intercalated polymer/LDH nanocomposites were obtained for the systems with additional 1173 except for LDH-1173 addition. Compared with the pure polymer material, both the exfoliated and intercalated polymer/LDH nanocomposites exhibited the enhancements in mechanical and thermal properties, as well as hardness.     

Application of high-pressure treatment on ovine brined cheese: Effect on composition and microflora throughout ripening

Ovine brined cheese was high-pressure (HP) treated at 200 or 500 MPa for 15 min at 20 °C on the 15th day of ripening. Compared to control cheese, HP treatment did not affect significantly (P > 0.05) the pH values, moisture, fat in dry matter, protein in dry matter and salt in moisture contents of cheeses at 90 days. The counts of total aerobic mesophilic bacteria, thermophilic lactococci, thermophilic lactobacilli and non starter lactic acid bacteria (NSLAB) were not affected by HP treatment of cheese at 200 MPa throughout ripening. After 90 days of ripening, the same microbial groups in cheese treated at 500 MPa were about 1.2, 3.6, 2.1 and 4 log units lower than in control cheese respectively. Coliforms were reduced faster at non detectable levels in HP treated cheeses than in control cheese. Regarding the bacterial enzymatic activities in cheese, aminopeptidase activity (Apep) was marginally favoured by both HP treatments. However, its activity was decreased at 90 days due probably to loss in brine. In contrast, lactate dehydrogenase (LDH) activity, following the bacteria cell lysis, was negatively affected by HP treatment at 500 MPa throughout ripening.Industrial relevanceThe data obtained from this work suggest that application of HP treatment under optimized conditions on ovine cheese in brine can be used to reduce effectively the undesirable microbial load in it and to cause moderate enhancement of aminopeptidase activity, without modifying its composition.     

Improving the Oxygen Evolution Activity of Layered Double-Hydroxide via Erbium-Induced Electronic Engineering

Layered double-hydroxide (LDH) has been considered an important class of electrocatalysts for the oxygen evolution reaction (OER), but the adsorption-desorption behaviors of oxygen intermediates on its surface still remain unsatisfactory. Apart from transition-metal doping to solve this electrocatalytic problem of LDH, rare-earth (RE) species have sprung up as emerging dopants owing to their unique 4f valence-electronic configurations. Herein, the Er is chosen as a RE model to improve OER activity of LDH via constructing nickel foam supported Er-doped NiFe-LDH catalyst (Er-NiFe-LDH@NF). The optimal Er-NiFe-LDH@NF exhibits a low overpotential (191 mV at 10 mA cm⁻²), high turnover frequency (0.588 s⁻¹), and low activation energy (36.03 kJ mol⁻¹), which are superior to Er-free sample. Electrochemical in situ Raman spectra reveal the facilitated transition of Ni-OH into Ni-OOH for promoted OER kinetics through the Er doping effect. Theoretical calculations demonstrate that the introduction of Er facilitates the spin crossover of valence electrons by optimizing the d band center of NiFe-LDH, which leads to the G_O-G_HO closer to the optimal activity of the kinetic OER volcano by balancing the bonding strength of *O and *OH. Moreover, the Er-NiFe-LDH@NF presents high practicability in electrochemical water-splitting devices with a low driving potential of and a well-extended driving period.     

Engineering NiO/NiFe LDH Intersection to Bypass Scaling Relationship for Oxygen Evolution Reaction via Dynamic Tridimensional Adsorption of Intermediates

Oxygen evolution reaction (OER) is a pivotal reaction in many technologies for renewable energy, such as water splitting, metal–air batteries, and regenerative fuel cells. However, this reaction is known to be kinetically sluggish and proceeds at rather high overpotential due to the universal scaling relationship, namely, the adsorption energies of intermediates are linearly correlated and cannot be optimized simultaneously. Several approaches have been proposed to break the scaling relationship by introducing additional active sites; however, positive experimental results are still absent. Herein, a different solution is suggested on the basis of dynamic tridimensional adsorption of the OER intermediates at NiO/NiFe layered double hydroxide intersection, by which the adsorption energy of each intermediate can be adjusted independently, so as to bypass the scaling relationship and achieve high catalytic performance. Experimentally, the OER overpotential is reduced to ≈205 mV at current density of 30 mA cm^?2, which represents the best performance achieved by state‐of‐the‐art OER catalysts.