LDHs对碳酸盐激发胶凝材料早期水化反应与力学性能的影响

碳酸盐激发胶凝材料具有低环境影响、易操作、良好材料性能等特点,但也存在抗压强度发展慢等问题,限制其在实际工程中的应用。本研究以层状双氢氧化物(LDHs)为关键改性材料,探究LDHs掺入后碳酸钠激发矿渣的早期性能,结合等温量热法、XRD、TG-DTG、SEM和压汞仪(MIP)等材料表征测试方法,系统分析LDHs对碳酸盐激发胶凝材料水化反应及产物的影响规律。研究结果发现,随着LDHs掺量的增加,碳酸钠激发矿渣早期水化反应速率显著提升。LDHs可作为纳米晶核位点促进水滑石和C-S-H凝胶生长,加快碳酸盐激发胶凝材料早期主要水化产物的生成。水化早期试样孔隙结构得到改善,其1 d抗压强度最高可达22 MPa。     

纳米层状双金属氢氧化物的制备及光催化性能研究进展

半导体光催化剂因其高效、生态友好、成本低等优点,可用于解决能源与环境问题。层状双金属氢氧化物(LDHs)是一类由两种或两种以上金属阳离子组成的金属氢氧化物,结构由主体层板和层间的插层阴离子及水分子相互交叠构成。LDHs纳米材料具有带隙可调、比表面积大、种类多样、成本低廉并且易与其他材料复合实现功能化等优点,因此LDHs纳米材料在光催化领域中表现出良好的应用前景。本文系统综述了近年来LDHs纳米材料的制备方法及其在光催化分解水制氢、吸附和降解有机染料,以及光催化还原二氧化碳等光催化领域的最新研究进展,为未来高性能LDHs基纳米催化材料的制备及催化性能调控提供了一定的参考。     

金属表面新型绿色海洋防污功能膜层的研究进展

海洋中金属设备的生物污损会引起许多问题,如设备的额外能量消耗、高额的维护成本以及严重的金属腐蚀破坏,给海洋工程带来很大损失。在金属表面构建防污膜层是解决其海洋生物污损问题的重要途径。概括了海洋防污膜层的发展历程与金属表面环境友好型防污膜层的研究进展,并重点介绍了新型海洋防污功能膜层及其研究方向。目前,金属表面新型海洋防污膜层的开发主要集中于结构防污和功能防污2个方面。在结构防污方面,在金属表面构建仿生微纳结构,并以低表面能物质修饰,形成超疏水表面,能够显著提高其抗海洋生物附着的能力,达到绿色防污的目的;在功能防污方面,在金属表面制备具有可控释放防污抗菌剂能力的功能膜层,可以实现在环境保护前提下的高效抗菌防污,是未来研究的发展方向。层状双金属氢氧化物（LDHs）和金属–有机骨架（MOFs）材料具有合成物选择多样、微观结构独特的特点,自身具备抗菌能力或负载大量防污抗菌剂的能力,并可实现防污抗菌剂的可控释放,有望成为具有理想抗菌功能的新型海洋防污剂负载材料。     

多元层状双羟基金属复合氧化物用作阻燃填料制备阻燃纸

以氯化镁(MgCl2.6H2O)、氯化铝(AlCl3.6H2O)、氯化锌(ZnCl2.6H2O)、氯化铁(FeCl3.6H2O)和碳酸钠(Na2CO3)为原料,采用共沉淀法制备了双羟基金属复合氧化物(LDHs,又称水滑石),包括二元Mg-Al-CO23--LDHs、三元Mg-Al-Zn-CO23--LDHs和四元Mg-Al-Zn-Fe-CO23--LDHs;将LDHs作为阻燃填料,用浆内添加法制备了一系列新型阻燃纸;通过红外光谱(FT-IR)、力学性能、燃烧性能等测试对LDHs和阻燃纸进行了表征。结果表明,采用多元LDHs作为阻燃填料所制备的阻燃纸,阻燃性能得到了明显改善,而且随着LDHs元素的增多,其阻燃性能更好。当三元Mg-Al-Zn-CO23--LDHs用量为30%时,阻燃纸可达到难燃级,氧指数达到25.3%。当四元Mg-Al-Zn-Fe-CO23--LDHs用量25%时,阻燃纸即可达到难燃级,氧指数高于25.0%;当四元-Al-Zn-Fe-CO23--LDHs用量30%时,阻燃纸的续燃时间为5 s,灼燃时间为30 s,炭化长度为95 mm,阻燃纸达到GB/T14656—2009的要求。     

Three-dimensional graphene-like carbon nanosheets coupled with MnCo-layered double hydroxides nanoflowers as efficient bifunctional oxygen electrocatalyst

As a multifunctional material with excellent performances, layered double hydroxides (LDHs) and their composites have broad application prospects in energy storage, catalysis, environmental protection, drug release and other fields. In this study, three-dimensional (3-D) graphene-like carbon nanosheets (AGC) were prepared by one-step synthesis method as active carrier materials, and then MnCo-LDHs nanoflowers assembled with ultrafine nanosheets were loaded on them to construct a newly 3-D architecture of AGC/MnCo-LDHs nanocomposites. The nanocomposites were characterized by XRD, SEM, TEM and XPS. The composite materials were assembled into OER and ORR electrodes for electrochemical measurements as efficient bifunctional catalysts. The favorable 3-D porous architecture (fast ion diffusion) of MnCo-LDHs and carrier effect of AGC (high electron conductivity) were the key contributing factors for their excellent electrochemical performances of nanocomposites.     

Exploration of electrocatalytic water oxidation properties of NiFe catalysts doped with nonmetallic elements (P,S, Se)

The introduction of non-metallic atoms (P, S, Se) has emerged as an effective way to improve the catalytic activity of transition metal based layered double hydroxides (LDHs) for oxygen evolution reaction. However, objective comparisons of the performance of heteroelement-doped catalysts are complicated by the lack of standardization both in the electrochemical tests and physicochemical analysis. Herein, we use a unified protocol for evaluating the catalytic activities of heteroelement-doped NiFe-LDHs and explore the reasons for the differences in their catalytic performance. Some regular results are found from comparing the properties of the heteroelement-doped catalysts: (1) the introduction of P/S/Se can optimize the redox behaviors of Ni species, which is conducive to regulating adsorption energy of intermediates and the formation of high-valent active sites; (2) the specific area of catalysts was expanded after heteroelements doping, ensuring a more favorable structure for heterogeneous catalysis; (3) All P/S/Se-doped catalysts showed better activities when compared to the original NiFe LDHs in alkaline solutions, and the catalysts doped with S showed the best performance (Se < P < S).     

Co and La supported on Zn-Hydrotalcite-derived material as efficient catalyst for ethanol steam reforming

Four samples of Zn-hydrotalcite containing different amounts of Co (5, 10, 20, and 30 wt%) have been synthesized and tested in the steam reforming of ethanol. The best results were obtained with the sample containing 20 wt% of Co (20CoHT), with a complete conversion of ethanol and yields to hydrogen close to the equilibrium (73 mol.%). The physicochemical characterization of the samples by DRX, BET area and TPR indicates that the excellent performance exhibited by the sample containing 20 wt% of Co is due to the higher percentage of reduced cobalt and lower crystallite size of metallic cobalt present in this sample (11 nm). Additional studies have been carried out to improve the stability of this catalytic material against deactivation by the incorporation of 1 wt% of La. Stability studies were carried out using an industrial alcoholic waste as feed. Deactivation after 24 h of reaction time was found lower for the catalyst containing La (20CoLaHT), confirming the positive effect of lanthanum on the catalytic stability. The results presented here show that it is possible to prepare a catalyst based on Co supported on Zn-hydrotalcite and promoted with La with improved ethanol conversion, high hydrogen selectivity, and high stability to produce hydrogen by the steam reforming of an industrial alcoholic waste without commercial value.     

层状双氢氧化物的制备、表征及其催化应用

层状双氢氧化物.(LDHs)是一类重要的层柱状材料,因具有特殊的层状结构和组成,在吸附、催化等领域都占有重要地位.本文论述了LDHs可调控性的结构,介绍了LDHs和柱撑LDHs的主要制备方法,概括了主要的表征方法以及LDHs在催化领域的应用.     

Tuning Surface Electronic Configuration of NiFe LDHs Nanosheets by Introducing Cation Vacancies (Fe or Ni) as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

Intrinsically inferior electrocatalytic activity of NiFe layered double hydroxides (LDHs) nanosheets is considered as a limiting factor to inhibit the electrocatalytic properties for oxygen evolution reaction (OER). Proper defect engineering to tune the surface electronic configuration of electrocatalysts may significantly improve the intrinsic activity. In this work, the selective formation of cation vacancies in NiFe LDHs nanosheets is successfully realized. The as‐synthesized NiFe LDHs‐V_Fe and NiFe LDHs‐V_Ni electrocatalysts show excellent activity for OER, mainly attributed to the introduction of rich iron or nickel vacancies in NiFe LDHs nanosheets, which efficiently tune the surface electronic structure increasing the adsorbing capacity of OER intermediates. Density functional theory (DFT) computational results also further indicate that the OER catalytic performance of NiFe LDHs can be pronouncedly improved by introducing Fe or Ni vacancies.     

负载型Ru催化剂的制备及加氢性能

通过Ru固载同水滑石修饰的Al2O3（HTc-Al2O3）合成的同步化，制得Ru-HTc-Al2O3，对其进行XRD、ICP-AES、SEM、HRTEM、BET、NH3-TPD和XPS表征，并将其用于对苯二甲酸二甲酯催化加氢制取1,4-环己烷二甲酸二甲酯。以溶液浸渍法制得Ru/HTc-Al2O3和Ru/Al2O3对照。结果表明：相较于Ru/Al2O3和Ru/HTc-Al2O3，Ru-HTc-Al2O3具有更大的比表面积（105.4 m2/g）；其大粒径Ru粒子的形成和Ru的损失受到明显抑制、Ru粒子尺寸分布集聚区间向小尺寸方向偏移，并可提供更多的表面酸性位，尤其是中性强度的酸性位。通过考察催化剂质量与原料DMT初始摩尔量的比例（CRR）、压力和温度的影响以及循环使用反应性能，发现催化反应活性顺序为：Ru-HTc-Al2O3 > Ru/HTc-Al2O3 > Ru/Al2O3；在CRR为100 g/mol，反应温度为180 ℃，反应压力为8 MPa时，Ru-HTc-Al2O3的催化性能达到最佳：DMT转化率为98.2%，DMCD选择性为96.9%。