Remote Synthesis of Layered Double Hydroxide Nanosheets Through the Automatic Chemical Robot

As a family of two-dimensional functional materials, layered double hydroxides(LDHs) have the characteristics of adjustable lamellar element type and proportion, variable interlamellar anion, controllable particle size and thickness, providing a robust platform for photo/electro/thermal-catalysis. With the continuous progress of materials science, the synthesis of LDHs is becoming more and more refined. Herein, to achieve the fine preparation of LDHs materials, especailly for the no-chemical/material researchers, we successfully assembled the automatic synthesis device and wrote corresponding computer software to control this device, and the automatic synthesis of bulk and monolayer LDHs nanosheets on a laboratory scale can be realized. This work paves a new labor-saving way for the fine synthesis of LDHs nanostructures, further improving the development of LDHs-based materials.     

Structure and stabilities of (HA1NH)n (n = 2–4)

Ab initio molecular electronic structure methods have been used to study the relative stability of the planar inorganic ring (HAlNH)_n (n = 2–4) during homodesmotic and monomer polymerization reactions. Optimized geometries, frequencies and energies through restricted Hartree-Fock/6-31G* are reported, and energies at the self-consistent field optimized geometries including M?ller-Plesset fourth perturbation theory with single, double and quadruple excitation (MP4SDQ) corrections are also reported for both reactions. Homodesmotic reactions with MP4SDQ −28.5 kcal/mol for (AlN)₂, 1.9 kcal/mol for (AlN)₃ and −0.97 kcal/mol for (AlN)₄. On analysing a π-molecular orbitals diagram, only one, three and three strongly bonding π-molecular orbitals exist for the planar four-, six- and eight-membered AlN rings, respectively. Received: 9 March 1998 / Accepted: 19 March 1998 / Published online: 23 June 1998     

Pd Loaded NiCo Hydroxides for Biomass Electrooxidation: Understanding the Synergistic Effect of Proton Deintercalation and Adsorption Kinetics

The key issue in the 5-hydroxymethylfurfural oxidation reaction (HMFOR) is to understand the synergistic mechanism involving the protons deintercalation of catalyst and the adsorption of the substrate. In this study, a Pd/NiCo catalyst was fabricated by modifying Pd clusters onto a Co-doped Ni(OH)₂ support, in which the introduction of Co induced lattice distortion and optimized the energy band structure of Ni sites, while the Pd clusters with an average size of 1.96 nm exhibited electronic interactions with NiCo support, resulting in electron transfer from Pd to Ni sites. The resulting Pd/NiCo exhibited low onset potential of 1.32 V and achieved a current density of 50 mA/cm² at only 1.38 V. Compared to unmodified Ni(OH)₂, the Pd/NiCo achieved an 8.3-fold increase in peak current density. DFT calculations and in situ XAFS revealed that the Co sites affected the conformation and band structure of neighboring Ni sites through CoO₆ octahedral distortion, reducing the proton deintercalation potential of Pd/NiCo and promoting the production of Ni³⁺−O active species accordingly. The involvement of Pd decreased the electronic transfer impedance, and thereby accelerated Ni³⁺−O formation. Moreover, the Pd clusters enhanced the adsorption of HMF through orbital hybridization, kinetically promoting the contact and reaction of HMF with Ni³⁺−O.     

Reducing the Ir−O Coordination Number in Anodic Catalysts based on IrOx Nanoparticles towards Enhanced Proton-exchange-membrane Water Electrolysis

Due to the robust oxidation conditions in strong acid oxygen evolution reaction (OER), developing an OER electrocatalyst with high efficiency remains challenging in polymer electrolyte membrane (PEM) water electrolyzer. Recent theoretical research suggested that reducing the coordination number of Ir−O is feasible to reduce the energy barrier of the rate-determination step, potentially accelerating the OER. Inspired by this, we experimentally verified the Ir−O coordination number's role at model catalysts, then synthesized low-coordinated IrO_x nanoparticles toward a durable PEM water electrolyzer. We first conducted model studies on commercial rutile-IrO₂ using plasma-based defect engineering. The combined in situ X-ray absorption spectroscopy (XAS) analysis and computational studies clarify why the decreased coordination numbers increase catalytic activity. Next, under the model studies’ guidelines, we explored a low-coordinated Ir-based catalyst with a lower overpotential of 231 mV@10 mA cm⁻² accompanied by long durability (100 h) in an acidic OER. Finally, the assembled PEM water electrolyzer delivers a low voltage (1.72 V@1 A cm⁻²) as well as excellent stability exceeding 1200 h (@1 A cm⁻²) without obvious decay. This work provides a unique insight into the role of coordination numbers, paving the way for designing Ir-based catalysts for PEM water electrolyzers.     

当前化学教学改革若干问题的意见

理科化学学科教学指导委员会会议 1 999年 1 2月中旬在合肥中国科技大学召开 ,会议就当前化学教学改革的若干问题进行了认真的讨论。现总结如下 ,供各校参考。1　关于教学改革立项　　教学指导委员会会议分析了当前教学改革的形势和存在的主要问题 ,认为原来化学专业、应化专业及非化学类专业化学教学的“面向 2 1世纪课程体系及教学内容改革”已取得了一定成果 ,处于结题验收阶段 ,但教学改革是一项长期任务 ,任重而道远 ,而实验教学改革、化学信息学课程建设及教学方式现代化等方面更是当前迫切需要解决的问题。　　 ( 1 )纵观当前化学实…     

中国大学化学教育改革25年回顾

1中国大学化学教育历史1.1萌芽时期(1865~1910年)中国人民在长期的生产劳动过程中积累了丰富的化学知识,形成了许多成功的化学工艺,如陶瓷、酿造、炼丹、医药、火药、造纸、纺织等,但由于历史原因,这些丰富的化学知识和成功的化学工艺并没有上升为理论而形成化学学科。化学作为一门科学诞生于17世纪的西欧,其标志为1661年波义耳对“元素”提出了科学定义,继而1803年道尔顿提出了原子论,1860年康尼查罗提出原子分子论,1870年门捷列夫发现元素周期律。至19世纪中,化学已发展成一门具有坚实理论的基础学科,化学对西方物质文明的发展起了巨大的…     

高校实验教学考核模式改革探索与实践

归纳了实验教学考核模式改革的一些经验,在此基础上,针对《网络攻防技术》课程实验的考核模式进行了改革,设计了网络攻防实验考核测评指标体系,构建了网络攻防实验考核平台,提出了全过程跟踪的实验考核评价方法,取得较好的实践效果.     

Size‐Dependent Surface Activity of Rutile and Anatase TiO2 Nanocrystals: Facile Surface Modification and Enhanced Photocatalytic Performance

The size‐dependent surface activity of titania was illustrated through the formation of ultrafine nanocrystals with clean surfaces. It was demonstrated that, when the size of the nanocrystals was small enough, their surface activity could be significantly enhanced, as evidenced by the formation of transparent macroassemblies, their increased dispersity in various solvents, the facile modification of their surface by organic molecules at room temperature, their strong visible‐light absorption through coordination with peroxide, and highly enhanced photocatalytic performance.