Facile synthesis of ordered mesoporous molybdenum carbide electrocatalysts for high-performance hydrogen evolution reaction

In this study, a simple method was designed to prepare ordered mesoporous carbons embedded with molybdenum without any extreme conditions. We prepared three different ordered molybdenum carbide materials with mesoporous structures to explore the influence of the structure of molybdenum-based materials on the HER catalytic efficiency. The ordered mesoporous molybdenum carbide catalysts (CMK-3-MoCx, fCMK-3-MoCx, CMK-8-MoCx) were characterized by SEM, TEM, XRD, nitrogen adsorption-desorption and XPS. The HER is catalyzed efficiently on the three electrocatalysts, fCMK-3-MoCx shows the best HER electro-catalytic performance with a small onset potential of −0.06 V vs. RHE, a low tafel slope of 66 mV dec⁻¹ and a small over-potential value of 89 mV at 10 mA cm⁻². This excellent performance on HER is due to its high specific surface area and highly ordered mesoporous structure that resulted in excellent proton transport efficiency and high electron transfer rate. Our results provide a new research direction for the application of flat ordered mesoporous structures in catalysis.     

双官能团硫脲催化丙交酯开环聚合反应的理论研究

用密度泛函理论在B3LYP/6-31G(d)水平上研究了双官能团硫脲催化丙交酯开环聚合反应的微观机理. 讨论了催化聚合反应的两条可能路径: 路径A和路径B. 计算结果表明沿路径A进行的开环聚合反应在能量上是有利的. 从理论上证实了催化剂在聚合反应中所起的双官能团催化作用, 即氨基活化引发剂, 硫脲活化单体, 通过两个基团共同作用, 完成催化开环.     

N,P‐Codoped Carbon Networks as Efficient Metal‐free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions

The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template‐free approach to three‐dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self‐assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal‐free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn–air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g^?1) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells.     

FeNi Layered Double‐Hydroxide Nanosheets on a 3D Carbon Network as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

An efficient electrocatalyst for oxygen evolution has been prepared via the deposition of iron–nickel layered double‐hydroxide (FeNi‐LDH) nanosheets on 3D carbon network as the building scaffold in a one‐step hydrothermal process. It is found that upon the assembling of FeNi‐LDH nanosheets with graphene into the 3D cross‐linked hybrid, the FeNi‐LDH/graphene hybrid features a well‐improved catalytic activity towards the oxygen evolution reaction (OER) with a good stability during the long‐term cycling experiment. Moreover, the hybrid catalyst is also active in the oxygen reduction reaction (ORR), qualifying it as a new type of bifunctional catalyst that can work in metal–air batteries.     

Efficient Synthesis of Dimethyl Ether from Methanol in a Bifunctional Zeolite Membrane Reactor

A sandwich FAU–LTA zeolite dual‐layer membrane has been developed and used as a catalytic membrane reactor for the synthesis of dimethyl ether (DME). In the top H‐FAU layer with mild acidity, methanol is dehydrated to DME. The other reaction product, water, is removed in situ through a hydrophilic Na‐LTA layer, which is located between the porous alumina support and the H‐FAU top layer. The combination of mild acidity with the continuous removal of water results in high methanol conversion (90.9 % at 310 °C) and essentially 100 % DME selectivity. Furthermore, owing to the selective and continuous removal of water through the Na‐LTA membrane, catalyst deactivation can be effectively suppressed.     

Effect of Initiator on the Incorporation of Graphite into Polymer Matrix During Suspension Polymerization

Summary: The incorporation of graphite into polystyrene (PS) particles produced by suspension polymerization was studied using a monofunctional and a bifunctional initiator, benzoyl peroxide (BPO) and 2,5-dimethyl-2,5-bis(2-ethyl hexanoyl peroxide) hexane (L256), respectively. The results showed that the polymerization rate was affected by graphite concentration when BPO was used as the initiator while no such effect was observed for L256. Results also showed that the incorporation of graphite in the PS particles was higher when using BPO than when using L256. Molecular weight distribution showed that during the reaction with BPO and graphite oligomers were formed indicating that the free radicals generated by the decomposition of BPO presented a very high reactivity with the functional groups present at the graphite surface while no significant effect was observed for the reaction with L256.     

精确可控串联策略触发高效的氧还原活性

探索高效、经济的非金属氧还原(ORR)电催化剂已成为电化学能源体系的关键.科学界最具挑战性的目标之一是通过合理地验证和精确地调节活性位点来设计结构明确、性能优异的催化剂材料.本文提出一种精确和可控的串联协同作用的活性位点策略,以提高MFCOFs的ORR催化活性.以亚胺-N、噻吩-S和三嗪-N等作为结构单元,通过精确的串...     

双通道离子色谱法同步检测DOPO中的无机离子

以氯仿溶解9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO),离心取清液,自动进样器-双通道离子色谱法同步检测DOPO中的无机阴阳离子,采用自动进样器与双通道同步进行,大大缩短了分析时间,离子保留时间的相对标准偏差RSD(n=6)在0.07%～0.18%,峰面积的RSD(n=6)在0.43%～0.88%,重现性好。3种离子的平均回收率在94.87%～98.30%,结果令人满意。     

石墨烯基催化剂的设计合成与电催化应用

为了解决能源匮乏和环境污染的问题,研究人员正致力于寻找清洁可持续的新能源。 其中,氧气还原、氧气析出、析氢反应等是紧密联系新型清洁能源获取和存贮的重要电化学反应。 为了提高其能量转化效率,电催化剂(如碳载铂Pt/C)被广泛地用于降低其反应活化能、提高能量转化效率。 近年来,石墨烯作为一种具有高比表面积和优异导电性的二维碳材料受到了广泛关注。 通过表面杂原子掺杂、缺陷调控和引入催化活性组分等方式,获得了催化性能与贵金属催化剂相媲美,且低价格和高稳定性的非贵金属石墨烯基催化材料。 针对氧气还原、氧气析出和析氢反应在燃料电池、金属-空气电池和电催化水分解中的应用,本文概括综述了通过表/界面结构性质调控提高石墨烯电催化性能和稳定性,获得具有双功能或复合催化性能的石墨烯基催化剂的最新研究进展。 最后总结和展望了亟待解决的问题及未来的发展趋势。     

An Organocatalytic Asymmetric Tandem Reaction for the Construction of Bicyclic Skeletons

Cyclic ketones react with (E)‐2‐nitroallylic acetates in the presence of catalytic pyrrolidine‐thiourea, which affords bicyclic skeletons with four or five stereocenters in one single reaction with up to 98 % ee in moderate to high yields. The cooperative effects of both enamine and the Brønsted acid are found to be crucial for the high reactivity and enantioselectivity of this cascade reaction, which is demonstrated by both theoretical calculation and experimental data.