TiO2纳米管限域Fe2O3的可见光分解水制氢性能

通过真空−超声辅助的等体积浸渍法制备了TiO2纳米管限域Fe2O3催化剂,考察了其可见光分解水制氢性能。由于TiO2纳米管的限域效应,导致Fe2O3颗粒减小,分散度提高,能隙增大,光生载流子得到有效分离,提高了其光解水制氢活性。     

Nb2C MXene衍生Nb2O5多层纳米片的快速合成及其在锂离子电容器中的性能

近年来,随着电动汽车和储能领域的快速发展,锂离子电容器(LICs)因其高功率密度和相对较高的能量密度而备受关注.五氧化二铌(Nb2O5)因具有高容量和优异的倍率性能等特点,而成为最重要的负极材料之一.然而,目前报道的Nb2O5基负极材料的合成均需要复杂的制造工艺或做特殊处理.因此,本工作开发了一种通过氧化多层Nb2C MXene材料快速合成多层Nb2O5纳米片的方法.借助X射线衍射谱(XRD)、扫描电子显微镜技术(SEM)、比表面积分析、X射线光电子能谱(XPS)和电化学技术等测试表征手段,对所制得的多层Nb2O5纳米片进行了表征.在高温煅烧的初始阶段,前驱体由Nb2C MXene材料转变为正交Nb2O5(T-Nb2O5),并保留了MXene材料的多层纳米片微结构.随着烧结时间的增加,转变为由伪六方Nb2O5(TT-Nb2O5)纳米颗粒组成的纳米片结构.与TT-Nb2O5纳米颗粒相比,多层T-Nb2O5纳米片电极显示出更高的比容量和更优异的倍率特性.同时,T-Nb2O5电极在半电池和锂离子混合电容器中都表现出优秀的循环性能.多层T-Nb2O5材料更加优异的储锂性能可能源于其多片层结构、准二维锂离子扩散通道和快速赝电容响应能力三者的协同作用.     

纳米非晶硅(na-Si:H)P-i-n太阳电池

该文报道了通过适当氢稀释(RH=15)和合适的衬底温度(Ts=170℃)下，用PECVD制备得到的宽带隙氢化纳米非晶硅(na-Si：H)薄膜，并将其用作pin太阳电池的本征层。经过电池结构和工艺条件的优化设计，在p／i，i/n界面插入渐变带隙缓冲层，制备出了glass／ITO／p—a-SiC：H／i—na-Si：H／n—nc-Si：H／Al结构的pin太阳电池。电池初始开路电压(Voc)高达0．94V，同时还能保证0．72的填充因子(FF)。光电转换效率(Eff)达到8．35％(AM1．5，100mW／cm^2)。     

新型太阳能制氢系统的分析与研究进展

本文对太阳能分解水制氢系统进行了理论和应用方面的分析，重点介绍了光解水的光热电化学分析。对近几年利用太阳能光解水制氢的进展进行了概述，并指出了它们目前存在的缺点。介绍了通过光热化学循环进行太阳能分解水制氢的新途径，并对未来的研究方向进行了展望。     

溶胶—凝胶法制备新型蓄能复合材料

用溶胶－凝胶法制备C17H35COOH－SiO2复合材料，并用透射电镜，扫描电镜，差示扫描量热分析等测试手段研究其结构与性能，结果表明，该复合材料是三维网络状纳米复合材料，而且具有良好的蓄热能力，可用于太阳能利用等方面。     

Ni-Co双金属催化剂上沼气重整制氢宏观动力学

用传统湿式浸渍法制备La2O3掺杂的商业γ-Al2O3负载的沼气重整催化剂Ni-Co/La2O3-γ-Al2O3,通过对NiCo双金属催化剂上沼气重整制氢在常压下的宏观动力学分析,得出该催化剂上CH4与CO2消耗、H2与CO生成时的表观反应速率方程.通过改变进料中CH4与CO2的分压,求出各物质的反应分级数,确定总反应...     

水溶性Fe_3O_4/Au纳米复合粒子制备及性能研究

本文针对可用作MRI/CT双模式成像分子探针的Fe3O4/Au纳米粒子制备方法存在工艺繁琐,工业扩大化后能耗大等缺点,发展了一种绿色、简便的可控自组装工艺,分析了纳米复合材料的微观结构特征,研究了材料的等离子体共振特性和磁学特征。结果表明:(1)发展的层层自组装方法可以使磁性纳米粒子Fe3O4与具有高X射线吸收的Au粒子组装在一起,两者结合牢固,长时间超声振荡后仍然没有脱落;(2)中心核为Fe3O4纳米团簇的结构特征使复合粒子具有高饱和磁化强度,克服了以往报道的Fe3O4/Au复合纳米粒子磁化强度低的缺点;(3)金粒子均匀分布在Fe3O4纳米团簇表面,因为粒子间距缩短增强了粒子间的耦合作用,使得等离子体共振谱发生了宽化和红移。     

光催化技术制氢的研究进展

直接利用太阳能光解水制氢对缓解未来能源危机有着重要意义,细述了利用光催化技术催化分解水制氢的反应机理,介绍了4种光催化剂和光催化反应的光源,分析了提高光催化性能的途径,展望了未来的研究方向.     

TiO2超声光催化降解荧光增白剂-CBW

均匀沉淀法制备了纳米TiO2，TEM，xRD分别进行了表征。以该纳米TiO2为光催化剂，对超声光催化降解荧光增白剂CBw的反应进行了研究。结果表明，超声波的引入提高了纳米TiO2光催化降解CBw的反应效率；反应符合Langmuir-Hinshelwood动力学模型，表观反应速率常数k1为0．0266min^-1；反应受超声波功率的影响；溶液中添加少量的Fe^3 ，H3PW12O40、H2O2均能够明显地强化CBw的降解反应。     

复合相变蓄能材料的研究与发展

本文介绍了复合相变蓄热材料和纳米复合材料的制备、特性、机理及国内外研究现状,并从节能、环保的角度出发,提出将纳米技术与复合相变蓄能材料结合,制备新型、高效的纳米复合蓄能相变材料。     

Cd1-xZnxS薄膜结构表征与光电化学性能研究

利用超声喷雾热分解方法在ITO导电玻璃上成功制备了高质量低成本的Cd1-xZnxS薄膜,并利用X射线衍射(XRD)、扫描电镜(SEM)、紫外可见光谱(UV-vis)等表征手段对其进行了结构、形貌和光学性质表征,并采用锁相放大技术研究了Cd1-xZnxS电极的光电流作用谱图。结果表明,利用喷雾热分解方法能制备出结晶完好均匀致密的Cd1-xZnxS薄膜,其中CdS呈六角相,Cd1-xZnxS(0相似文献   

Enhanced hydrogen storage properties and mechanisms of magnesium hydride modified by transition metal dissolved magnesium oxides

Magnesium hydride (MgH₂) is a promising on-board hydrogen storage material due to its high capacity, low cost and abundant Mg resources. Nevertheless, the practical application of MgH₂ is hindered by its poor dehydrogenation ability and cycling stability. Herein, the influences and mechanisms of thin pristine magnesium oxide (MgO) and transition metals (TM) dissolved Mg(TM)O layers (TM = Ti, V, Nb, Fe, Co, Ni) on hydrogen desorption and reversible cycling properties of MgH₂ were investigated using first-principles calculations method. The results demonstrate that either thin pristine MgO or Mg(TM)O layer weakens the MgH bond strength, leading to the decreased structural stability and hydrogen desorption energy of MgH₂. Among them, the Mg(Nb)O layer exhibits the most pronounced destabilization effect on MgH₂. Moreover, the Mg(Nb)O layer presents a long-acting confinement effect on MgH₂ due to the stronger interfacial bonding strength of Mg(Nb)O/MgH₂ and the lower brittleness of Mg(Nb)O itself. Further analyses of electronic structures indicate that these thin oxide layers coating on MgH₂ surface reduce the bonding electron number of MgH₂, which essentially accounts for the weakened MgH bond strength and enhanced hydrogen desorption properties of modified MgH₂ systems. These findings provide a new avenue for enhancing the hydrogen desorption and reversible cycling properties of MgH₂ by designing and adding suitable MgO based oxides with high catalytic activity and low brittleness.     

定壁温下甲烷自热重整产氢暂态特性数值模拟

采用甲烷自热重整的详细反应机理,通过数值模拟的方法研究了恒壁温、微型直通道内的CH4、O2、H2O镍基催化剂上的自热重整反应。重点分析了混合物组分及质量流量对自热重整产氢暂态特性的影响。结果表明,在较高温度下,微型反应器出口H2产量达到最大值所需的时间受混合气质量流量影响较大,而受混合物组分影响很小;氢气产量达到稳定所需的时间随H2O、CH4摩尔比的增大而缩短,随O2/CH4摩尔比的增大而增长。CH4/O2/H2 O摩尔比为1∶0.5∶3.5时,氢气体积分数可在90 ms时稳定于54%。     

Study on the hydrogen storage properties of a TiZrNbTa high entropy alloy

High-entropy alloys (HEAs), as a new class of metallic materials, have received more and more attention due to its excellent mechanical properties. In this study, the hydrogen absorption properties, such as hydrogen absorption capacity, thermodynamics, kinetics and cyclic properties, as well as the hydride structure of a newly designed TiZrNbTa HEA were investigated. The results showed that multiple hydrides including ε-ZrH₂, ε-TiH₂ and β-(Nb,Ta)H were found in the TiZrNbTa HEA after hydrogenation. With the increase of temperature from 293 K to 493 K, the maximum hydrogen absorption capacity decreased from 1.67 wt% to 1.25 wt% and the plateau pressure related with β-(Nb,Ta)H hydrides increased from 1.6 kPa to 14.8 kPa. The formation enthalpy of β-(Nb,Ta)H hydride was determined to be −6.4 kJ/mol, which was less stable than that of NbH and TaH hydrides. The results also showed that the TiZrNbTa HEA exhibited a rapid hydrogen absorption kinetic even at the room temperature with a short incubation time, and the hydrogen absorption mechanism was determined to be the nucleation and growth mechanism. Moreover, the hydrogen absorption capacity at 293 K decreased slowly with the cycle numbers, and remained 86% capacity after 10 cycles. Cracking occurred after hydrogen absorption and became worse with cycles.     

Photocatalytic production of hydrogen and methane from glycerol reforming over Pt/TiO2–Nb2O5

In this study, platinized mixed oxides (TiO₂–Nb₂O₅) were tested on photocatalytic hydrogen production from a glycerol solution under UV light. Different samples with different Ti:Nb ratios were prepared by using a simple method that simultaneously combined a physical mixture and a platinum photochemical reduction. This method led to improved physicochemical properties such as low band gap, better Pt nanoparticle distribution on the surface, and the formation of different Pt species. Niobia content was also found to be an important factor in determining the overall efficiency of the Pt–TiO₂–Nb₂O₅ photocatalyst in the glycerol reforming reaction. The photocatalytic results showed that Pt on TiO₂–Nb₂O₅ enhanced hydrogen production from the aqueous glycerol solution at a 5 wt% initial glycerol concentration. The influence of different operating conditions such as the catalyst dosage and initial glycerol concentration was also evaluated. The results indicated that the best hydrogen and methane production was equal to 6657 μmol/L and 194 μmol/L, respectively after 4 h of UV radiation using Pt/Ti:Nb (1:2) sample and with 3 g/L of catalyst dosage. Moreover, the role of water in photocatalytic hydrogen production was studied through photocatalytic activity tests in the presence of D₂O. The obtained results confirmed the role of water molecules on the photocatalytic production of hydrogen in an aqueous glycerol solution.     

Enhanced hydrogen production properties of a novel aluminum-based composite for instant on-site hydrogen supply at low temperature

Al-water reaction for hydrogen production faces the problems of long induction time and low conversion efficiency at low temperature (below 273.15 K), which has seriously limited its applications. To realize the instant hydrogen production of Al composites at low temperature, low melting point metals (Ga, In, Sn) and additives (NaCl, g-C₃N₄, LiH) were selected to prepare Al composites with high reactivity. Compared with the other Al composites, Al alloy/NaCl/LiH/g-C₃N₄ composites exhibit the enhanced low temperature hydrogen production performance in 23 wt% NaCl aqueous solution at 253.15 K. For all Al alloy/NaCl/LiH/g-C₃N₄ composites, the induction time of Al-water reaction at 253.15 K has completely eliminated. The highest hydrogen generation volume of 1095 mL·gAl^?1 and the maximum hydrogen generation rate of 120 mL·gAl^?1·s^?1 were obtained for Al alloy/NaCl/1.5%LiH/g-C₃N₄ composite. It is proposed that LiH can induce Al-water reaction instantly starting at 253.15 K. The released heat and micro alkaline environment further promote the Al-water reaction and enhance the hydrogen conversion efficiency. In particular, g-C₃N₄ additive can improve the antioxidant properties of Al composites. This study provides a novel way for the development and application of Al composites in real-time hydrogen production at low temperature.     

Hydrogen production by aluminum corrosion in aqueous hydrochloric acid solution promoted by sodium molybdate dihydrate

Recycled aluminum alloys corrosion system was studied for hydrogen production in 1.4 M HCl solution at low temperature, 333 K. Molybdate ions were used as corrosion promoter. Commercial Na₂MoO₄·2H₂O was tested, varying its concentration (0–0.036 M) in order to analyze the promoter effect in H₂ production. Moreover, Na₂MoO₄·2H₂O particles were synthesized via sonochemical method and by ultrasonic method. Later, synthesized promoters were tested in order to analyze the effect of their physicochemical properties in H₂ production. Gas composition produced during the reaction was analyzed by gas chromatography. Results showed that reaction rate was notorious affected by molybdate ions concentration. The highest hydrogen volume and the greatest reaction rate obtained was with the use of 1050 aluminum foil alloy with very low promotor concentration (0.004 M), becoming, therefore, a low-cost process for high purity hydrogen production.     

Kinetics and thermodynamics of hydrogenation-dehydrogenation for Mg-25%TM (TM = Ti,Nb or V) composites synthesized by reactive ball milling in hydrogen

0.75Mg?0.25TM?H (TM = Ti, Nb or V) samples were mechano-chemically synthesized by reactive ball milling. The detailed reaction mechanism during hydrogen release and uptake was investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) experiments. The thermodynamic and kinetic properties have been studied by Sievert's method. On the base of calculated values of the Gibbs free energy for reaction of hydrogen absorption (ΔG < 0) it reveals that hydrogenation reaction could thermodynamically proceed at room temperature, which is experimentally confirmed for all of the studied composites. It is clearly shown that β-MgH₂ forms at RT under conditions of experiment. Comparative analysis of the MgTi, MgV and MgNb systems makes it possible to establish that the most effective additive facilitating hydrogen uptake, particularly at RT, is vanadium. It provides the degree of conversion into hydride phase α = 0.86 for the first minute of hydrogenation. In contrast, additives of Nb and Ti provide only α = 0.62 and 0.36, respectively, following the 30 min of exposure. However, this study reveals that for the dehydrogenation process, titanium is the best among the examined additives, which is evidenced by lowest value of activation energy E_a = 53.6 kJ/mol of the hydrogen desorption.     

Characteristics of a phototrophic sludge producing hydrogen from acetate and butyrate

A mixed phototrophic sludge was enriched from the sediment of a local river for continuous hydrogen production from acetate and butyrate in a complete-mix reactor. At pH 7.0–7.5 and , the optimal hydrogen production rate at 48 h of hydraulic retention time (HRT) for 150 days of steady-state operation averaged with of biomass. The sludge yield averaged -VSS/g-COD. Results of batch experiments showed an optimal pH of 8.5 and an optimal concentration of 2 mM for hydrogen production. At 10 mM, severely inhibited the hydrogen production. Three of the five OTUs classified from 26 clones developed from the seed sludge were phototrophs, based on phylogenetic analysis. Among them, OTU LA15, which is closely related to Rhodobacter sp., was most likely responsible to the hydrogen production.     

Production of hydrogen by direct thermal decomposition of water

This paper reports the first results of a study on the feasibility of producing hydrogen by direct thermal splitting of water by use of concentrated radiation. Relative amounts of H, O, OH, H₂, O₂ and H₂O have been computed between 1500 and 4000 K at thermodynamic equilibrium. In addition, the rate of the overall reaction has been estimated assuming a kinetic model: 90% of equilibrium concentrations are reached after about 10^?2, 10^?3 and 10^?4s at 2200, 2500 and 3000 K respectively. The dissociation experiments have been carried out in an image furnace, simulating the future use of a solar furnace. Water is injected through a zirconia nozzle heated at the focus. The hot jet containing active species is then quenched by turbulent cold jets in order to minimize recombinations. Several shapes of zirconia nozzles and quenching devices have been tested in order to maximize the net production of hydrogen, which reaches 1.7 STP l. h^?1 in continuous operation. Modelling of the hot nozzle allows the calculation of the gas temperature and shows that thermodynamic equilibrium conditions are reached under certain conditions. Parallel experiments show that cooling rates up to 10⁶ Ks^?1 can be obtained by quenching.