Doping manganese into CsPb(Cl/Br)3 quantum dots glasses: Dual-color emission and super thermal stability

CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (QDs) represent bright and tunable photoluminescence, it is regrettable that the air instability and poor water resistant properties prevent their application in optoelectronic devices. At the same time, the toxicity of lead is also a major factor restricting its development. As a consequence, we demonstrate the partial replacement of Pb with Mn through conventional melt-quenching and heat-treatment method preparation of Mn-doped CsPb(Cl/Br)₃ QD glass. Mn-doped CsPb(Cl/Br)₃ QD glass exhibits high luminescent intensity like QDs. It is important that Mn-doped CsPb(Cl/Br)₃ QD glass with Dual-Color maintained the same lattice structure like Mn-doped CsPb(Cl/Br)₃ QDs, and highly homogeneous spectral characteristics of Mn luminescence. The intensity and position of this Mn-related emission are also tunable by altering the experimental parameters, such as the Pb-to-Mn feed ratio, annealing temperature. More importantly, the as-prepared orange Mn-doped CsPb(Cl/Br)₃ QD glass was employed to fabricate white LEDs combined with a commercial Ce³⁺:Y₃Al₅O₁₂ phosphor-in-glass (Ce-PiG) on top of a InGaN blue chip. And the constructed WLEDs generate a warm white with an optimal luminous efficacy (LE) of 67.00 lm/W, a high CRI of 81.4, and a low CCT of 4902 K.     

Kinetics and mechanistic studies of methane dry reforming over Ca promoted 1Co–1Ce/AC-N catalyst

The mechanism and kinetic features of dry reforming with methane (DRM) over Ca promoted 1Co–1Ce/AC-N catalyst was investigated. The mechanistic pathway studies have conducted by FTIR and XPS analysis, structure-activity correlations demonstrated the CH₄ and CO₂ could adsorb on catalyst active sites and generate intermediate CH_x, OH and CH_xO, continue to generate CO and H₂ and then desorbed from active sites. Moreover, CH₄ could also oxidized by Ce⁴⁺ and CO₂ reduced by Ce³⁺, the same content of Ce⁴⁺ and Ce³⁺ on promoted catalyst greatly improved the reaction rate. The kinetic of dry reforming with methane was examined for temperature between 650 and 850 at 800 °C. The research was carried out by changing the CH₄/CO₂ ratios between 0.3 and 3.0. The obtained experiment data were fitted by three typical kinetic models (Power Law, Eley-Rideal and Langmuir-Hinshelwood), the fitting results demonstrated that the best prediction of reforming rates can provided by Langmuir-Hinshelwood model for the reaction temperatures between 650 and 800 °C. Moreover, activation energies of methane and carbon dioxide consumption were ?117 and ?47 kJ/mol, indicating that much higher energy barrier is needed for methane activation compared to carbon dioxide.     

金属Ce氢化-氮化反应动力学

以金属Ce为原料，对Ce氢化-氮化动力学参数进行研究，分别考察了初始反应温度、原料气体初始压力和Ce片厚度等对金属Ce氢化-氮化反应的影响。研究结果表明：升高初始反应温度有利于缩短氢化过程的诱导时间，但对氢化反应速率无明显影响；提高H₂初始压力和降低片层厚度能明显加快氢化反应速率。此外，通过X射线衍射（XRD）和扫描电镜（SEM）等表征证明氢化铈可以与N₂反应得到氮化铈（CeN）和H₂，但反应需要较高的温度以克服活化能，增加初始反应温度和N₂初始压力可以提高反应速率。综合考虑，初始反应温度为350 ℃、N₂初始压力为60 kPa是氢化铈氮化的较优条件。     

Dual effect synergistically triggered Ce:(Y,Tb)3(Al,Mn)5O12 transparent ceramics enabling a high color-rendering index and excellent thermal stability for white LEDs

Ce:Y₃Al₅O₁₂ transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce³⁺ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)₃(Al,Mn)₅O₁₂ TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb³⁺ and Mn²⁺ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb³⁺ ion and the energy transfer between Ce³⁺ and Mn²⁺ ions were verified in prepared TCs.     

Nitrogen oxides reduction by liquid petroleum gas over Co–Ce–Ti catalysts in a simulated rotary reactor

Hydrocarbons could be used as the reductant for elimination of NO_x emissions. Liquid petroleum gas, with higher carbon hydrocarbons and cheaper costs, may be of practical value as reducing agents. Due to the consumption of hydrocarbons by oxygen, the NO_x reduction efficiency is significantly inhibited by oxygen in the flue gas. In this research, a novel rotary reactor, realizing the alternating cycle of adsorption zone and reduction zone, was proposed to overcome this negative effect. Co–Ce–Ti mixed oxide catalysts synthesized by a sol–gel method were tested in a simulated rotary reactor for NO_x removal by liquid petroleum gas and characterized by SEM, BET, XRD and XPS. The results showed that catalysts exhibited better NO conversion efficiency at higher temperature but were highly susceptible to oxygen. Catalysts achieved nearly full removal of NO_x from flue gas at 300 °C in a simulated rotary reactor, and 300 °C is considered to be the most optimum temperature with lower energy consumption and excellent flue gas purification performance.     

Unraveling the effect of alumina-supported Y- doped ceria composition and method of preparation on the WGS activity of gold catalysts

The demands for high-purity hydrogen required in fuel-cell applications impose new goals and challenges for design of well performing water-gas shift (WGS) catalysts. Gold-based catalysts have exhibited high activity in the WGS reaction at low temperature. Preparation of appropriate and economically viable supports with complex composition by various synthesis procedures is an attractive approach to WGS performance improvement. The effect of two different preparation methods (wet impregnation or mechanical mixing) and ceria content (10, 20 or 30 wt%) on textural, structural, surface and reductive properties and WGS activity of gold catalysts was studied. Additionally, the role of Y₂O₃ as a promoter of ceria was examined. Long-term stability test was carried out at 260 °C over the most active catalyst. The composition of the best performing sample (composed of about 70 wt% alumina), prepared by mechanical mixing, was considered promising in case of practical applications because of its cost efficiency. The combination of gold nanoparticles and alumina supported Y-doped ceria proved an advantageous approach for developing new catalytic formulations with high effectiveness in clean hydrogen production.     

Ce-based organic framework enhanced the hydrogen evolution ability of ZnCdS photocatalyst

Ce-based organic framework materials [UIO-66(Ce)] were prepared, and the UIO-66(Ce)/ZnCdS composite was attained by microwave irradiation. Moreover, the photocatalytic hydrogen production activity was evaluated. The experimental results revealed that the ZnCdS nanoparticle was decorated on the surface of UIO-66(Ce), and the hydrogen production ability of ZnCdS nanoparticle was improved by UIO-66(Ce) significantly. The hydrogen production yield of UIO-66(Ce)/ZnCdS reaches 3.958 mmol/g·h, in which is as about 1.95 times as that of ZnCdS (2.031 mmol/g·h). The improvement for photocatalytic hydrogen production yield is because UIO-66(Ce) can facilitate the photoinduced carriers to separating.     

A simple Ce-doping strategy to enhance stability of hybrid symmetrical electrode for solid oxide fuel cells

Symmetrical solid oxide fuel cell (SSOFC) is a simple and very promising cell for the rest of the most important commercialization process, which has been longing for stable and efficient symmetrical electrodes, from single-phase perovskites to reducible perovskites with in-situ exsolved metal nanoparticles. Herein, we present a new-type hybrid symmetrical electrode consisting of two different perovskite phases for SSOFC, which interact by dynamic compositional change and accordingly improve the electrochemical activity. Furthermore, a simple Ce-doping strategy is successfully developed to solve the redox stability issue of the hybrid symmetrical electrode for SSOFC. Typical Gd_0.65Sr_0.35Co_0.25Fe_0.75O_3-δ (GSCF) consisting of a cubic perovskite phase and an orthorhombic perovskite phase is chosen as a proof-of-concept. Gd_0.65Sr_0.35(Co_0.25Fe_0.75)_0.9Ce_0.1O_3-δ (Ce-GSCF) with an optimized Ce content of only 10% exhibit the enhanced chemical and thermal stability, consisting of a cubic perovskite phase, an orthorhombic perovskite phase and an in-situ exsolved cubic fluorite phase (GDC). More importantly, Ce-GSCF exhibits very high stability in H₂ at 700 °C and a dramatical reduction of averaged thermal expansion coefficient from 19.5 × 10⁻⁶ K⁻¹ to 16.4 × 10⁻⁶ K⁻¹. The single-cell with Ce-GSCF hybrid symmetrical electrode reaches a high maximum power density of 224 mW/cm² at 700 °C, and can work stably for 180 h without any degradation, indicating that the simple Ce-doping strategy is promising to improve stability of hybrid symmetrical electrode for SOFCs.     

玻璃沉积物对La2Ce2O7/YSZ涂层高温下热冲击性能的影响

目的 为了探究玻璃沉积物CMAS(CaO-MgO-Al2O3-SiO2)对新型结构热障涂层在1250 ℃下的热冲击寿命的影响，揭示热障涂层的失效行为。方法 通过火焰喷涂技术将制备的CMAS粉体均匀地沉积到铈酸镧/氧化钇部分稳定二氧化锆双陶瓷层热障涂层(LC/YSZ DCL-TBCs)和梯度热障涂层(LC/YSZ FGM-TBCs)的表面，于1250 ℃热冲击实验中进行涂层样品的抗热冲击性能及失效机理研究。利用扫描电镜(SEM)和能谱仪(EDS)追踪CMAS的位置，观察CMAS与涂层反应层的厚度与形貌。采用X射线衍射仪(XRD)测试反应层产物，并总结其失效方式。结果 高温热冲击结果显示梯度涂层的热冲击寿命(435次)远高于双陶瓷层热障涂层的寿命(229次)，约为铈酸镧/氧化锆双陶瓷层热障涂层寿命的1.9倍。铈酸镧层与梯度层都能在一定程度上阻碍CMAS渗入涂层内部，提高其CMAS腐蚀条件下的热冲击寿命。双陶瓷层热障涂层与梯度热障涂层的失效均是以层状剥落为主，剥落层主要是CMAS与LC的反应层以及反应层下的烧结层，反应层是由Ca2(LaxCe1-x)8(SiO4)6O6-4x、萤石相和MgAl2O4等难熔氧化物组成，这层致密氧化物类似于密封层，能阻止CMAS继续渗入。结论 功能梯度结构具有比双陶瓷层结构更优异的抗CMAS热冲击性能和更好的应力耐受性。