Effects of pH on the PtRu/C Catalyst Prepared by Microwave-assisted Ethylene Glycol Process

以微波协助乙二醇工艺合成了碳负载不同粒径大小的PtRu/C纳米催化剂,主要考察了溶液pH值对PtRu粒子大小的影响.利用紫外可见光谱、能量散射X射线谱、透射电镜和X射线衍射谱对PtRu纳米催化剂进行了表征.结果表明,pH值是一个对PtRu粒子大小有着重要影响的因素.TEM结果显示随着溶液pH值的增加,PtRu粒径从3.5nm减小到1.5nm.当溶液pH值达到11.0时,由于金属粒子被保护,合成的催化剂中金属载量明显减少.溶液pH值在9.0左右合成的PtRu/C催化剂具有适宜粒径(2.4nm)和均匀分布的金属颗粒,具有最好的甲醇电氧化活性.PtRu nanoparticles supported on the carbon, with different mean particle sizes, were synthesized by microwave-assisted ethylene glycol process, the effects of pH on the PtRu/C catalyst were mainly investigated. UV-Vis spectroscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction were applied to characterize the PtRu nanoparticles. The solution pH had important influence on the metal particle size. TEM results indicated that the PtRu mean particle size decreased from 3.5 nm to 1.5 nm with the increase of pH value. However, when pH value reached 11.0, the metal loading of synthesized catalyst decreased distinctly because the metal nanoparticles were protected in solution. The results showed that the PtRu/C catalyst synthesized at pH ca 9.0, with appropriate particle sizes (2.4 nm) and homogenous dispersed particles, had the highest electrocatalytic activity for methanol electrooxidation among all the synthesized catalysts.国家自然科学基金(20673089);; 福建省科技重大专项(2005HZ01_3)资助项

大学基础课教师职称评定的误区与出路

随着大学基础课教学交接的全面展开,也同时出现两种值得注意的偏向,文中指出这些倾向的表现手法、错误实质以及应当树立的科学哲学观.文章还阐明:为了凝聚力量深化基础课教改、提高教学质量,就不应该在职称评定的问题上处处难为至今仍勤奋于基教第一线的中老年教师,而是应该创造和谐竞争环境,制订出科学的合情合理的晋升标准,提倡无形竞争,倡导不比意识

Synthesis,structure and electrochemical performance of Mg-doping nickel oxyhydroxide

首次以掺杂Mg的β-nI(OH)2为前驱体,采用k2S2O8为氧化剂,制备出β-羟基氧化镍镁,并应用X射线衍射光谱法(Xrd)、傅里叶变换红外光谱法(fTIr)、热重-差热分析(Tg-dTg)、CV和放电测试对样品的结构和电化学性能进行了表征。The Mg-doping β-NiOOH was firstly synthesized by using Mg-doping β-Ni(OH)2 as precursor,K2S2O8 as oxidizer.The crystal structure and electrochemical performance of the prepared samples were analyzed by XRD,FTIR,TG-DTG,CV and discharge test

Preparation of LiNi_(0.9)Co_(0.1)O_2 material and study on its electrochemical performance

成功采用掺杂和改变前驱体两种方式同时对传统lInIO2正极材料合成进行改进,即用掺杂10%WTCO的β-nIOOH作为前驱体,和lIOH·H2O在空气中进行固相烧结。通过正交方法优化出合成lInI0.9CO0.1O2的最佳烧结温度为600℃,烧结时间为24H;此条件下材料首次充放电效率高达86%,20次循环后可逆放电比容量为167MAH/g,容量保持率高达94%。It is a success for using both doping and changing precursor to improve the traditional cathode material LiNiO2 which is using 10%wt Co doped in the β-NiOOH as the precursor, then solid- phase Sintering with LiOH·H2O in the air.By orthogonal methods we optimize the best sintering temperature is 600 ℃ and sintering time is 24 h for synthesis of the LiNi0.9Co0.1O2; Under these conditions, the first charge and discharge efficiency can be as high as 86%, discharge capacity is to be 167 mAh/g after 20 cycles reversible, and the capacity rates can maintain as high as 94%

The performance of passive DMFC

研制了两只单体电池串联的被动式直接甲醇燃料电池(DMFC),无外部泵等辅助设施。考察了甲醇的浓度和温度、空气提供方式对单体电池性能的影响及单体电池的长期运行性能。单体电池在室温(25℃)下,贵金属载量为2.5 mg/cm2、甲醇浓度为3 mol/L时,性能最佳,峰值功率密度可达10 mW/cm2。提高甲醇温度和采用流动的空气,可提高电池的性能。单体电池在无水热管理系统1、00 mA放电的条件下,可在室温下连续、稳定地工作4 h。A passive direct methanol fuel cell(DMFC) with two single cells in series without auxiliary devices such as external pumps was designed and fabricated.The effects of methanol concentration and temperature,the air supply mode on the performance of single cell and the long-time operation performance of single cell were investigated.The single cell had optimal performance at room temperature(25 ℃) with 3 mol/L methanol and the noble metal loading was 2.5 mg/cm2,the peak power density could reach 10 mW/cm2.The increasing of methanol temperature and using flowing air could improve the performance of the cell.The single cell could work stably and continuously for 4 h at room temperature under the condition without water and thermal management systems and 100 mA discharge

氧化石墨烯改性高温环氧树脂基碳纤维复合材料的热性能与力学性能

采用湿法预浸技术和模压工艺,制备了氧化石墨烯(GO)改性碳纤维/环氧树脂(CF/E54-DDS)混杂复合材料,利用差示扫描量热分析(DSC)、动态热机械分析(DMTA)、无损C扫描等开展了GO对复合材料的热固化性能、凝胶工艺性、动态热机械性能以及抗冲击损伤性能等的影响研究。结果表明,GO结构中的羟基、羧基会促进改性树脂体系的固化反应,GO/E54-DDS的固化反应比E54-DDS的提前,反应变得和缓,且会加速固化反应的进行;在GO含量小于0.5%时,GO的活性基团可增加改性体系的交联密度而提高复合材料的玻璃化转变温度,但GO含量大于0.8%时,会因DDS在固化网络结构中的占比下降较大,反而降低复合材料的玻璃化转变温度;GO/CF/E54-DDS预浸料比CF/E54-DDS表现出更好的浸润效果;CF/E54-DDS复合材料破坏后碳纤维表面光洁,破坏主要发生在碳纤维与树脂基体的界面,而GO/CF/E54-DDS复合材料破坏后,碳纤维表面紧密粘附着GO/E54-DDS固化物,破坏主要发生在碳纤维织物层间的GO/E54-DDS区域;GO的存在提高了GO/CF/E54-DDS复合材料抵抗横向裂纹和纵向裂纹扩展的能力,复合材料的损伤投影面积和凹坑深度减小,提高了冲击后压缩强度。航空科学基金(2016ZF68011);;福建省科技创新平台建设计划(2014H2006);;福建省自然科学基金(2015J01222);;厦门大学石墨烯工业技术研究院资助项目(2014I2005

旋光度法测定蔗糖转化反应速率常数实验用旋光管的改进

用旋光度法测定蔗糖转化反应速率常数是最基本的物理化学实验之一。该实验中的旋光管操作比较麻烦,且易引入实验误差。本文对该实验使用的旋光管进行了改进

Structure and electrochemical performance of Mg-doping nickel hydroxide

采用化学共沉淀法制备出不同含量Mg掺杂的氢氧化镍样品。应用X-射线衍射(XRD),傅里叶变换红外光谱(FTIR)和热重分析(TG)手段对样品的结构进行了表征,并用循环伏安法研究了样品的电化学性能。结果表明:与Mn、Al等元素掺杂到一定含量后使Ni(OH)2晶型由!型转化为"型不同,即使Mg掺杂含量达到30%,样品仍为#型。但样品晶格产生畸变,晶粒尺寸随Mg含量的增加先变小后增大,电化学性能随Mg含量的增加先变好后变坏。Mg最佳含量为5%左右,此时OH-数量增多,产生了大量的晶格畸变,c轴拉长,有利于质子扩散系数的变大,增强了反应的可逆性,提高了电极充电效率和活性物质的利用率,从而改善了电极的电化学性能。The different amount of Mg-doping Ni(OH)2 samples were prepared by a coprecipitation method. The crystal structures were characterized by XRD, FTIR and TG methods. The electrochemical performances were also investigated by cyclic voltammetry method. The results show that even the Mg-doping content reaches 30%, the sample still is β-phase, which is different from Mn-doping or Al-doping samples in which the samples are changed to α-phase from β-phase when the doping amount reaches some levels. The distortion of crystal lattices are happened. The size of crystalline grains diminishes and then increases, and the electrochemical performances also are better and then worse when the Mg-doping amounts increases. The suitable Mg-doping amount is about 5%. In this case, the number of OH-increases, the crystal lattice distortion is engendered, and the interlayer distance c is stretched, which are favorable to enhancement of the proton transfer between electrode materials. Therefore, the reversibility of electrode reaction is improved, the charge efficiency is increased and the utilization of active materials is promoted, which results in improvement of electrochemical performance

Effects of pH on the PtRu/C catalyst prepared by microwave-assisted ethylene glycol process

PtRu nanoparticles supported on the carbon, with different mean particle sizes, were synthesized by microwave-assisted ethylene glycol process, the effects of pH on the PtRu/C catalyst were mainly investigated. UV-Vis spectroscopy, energy dispersive X-ray analysis, transmission electron microscopy, and X-ray diffraction were applied to characterize the PtRu nanoparticles. The solution pH had important influence on the metal particle size. TEM results indicated that the PtRu mean particle size decreased from 3.5 nm to 1.5 nm with the increase of pH value. However, when pH value reached 11.0, the metal loading of synthesized catalyst decreased distinctly because the metal nanoparticles were protected in solution. The results showed that the PtRu/C catalyst synthesized at pH ca 9.0, with appropriate particle sizes (2.4 nm) and homogenous dispersed particles, had the highest electrocatalytic activity for methanol electrooxidation among all the synthesized catalysts

Improvement on Liquid Saturated Vapor Pressure Measurement

针对目前静态法测定液体饱和蒸汽压实验中饱和蒸汽压数值读取不合理,汽液两相未充分平衡等问题,改变传统的调整u型管两端液面等高后再读取数字压力计的方法。改进后的实验装置只需在u型管的两侧标上刻度,待系统恒温、汽-液充分平衡后,读取数字压力计的数值、温度以及u型管两端液面的高度差就可得到该温度下的液体饱和蒸汽压。该方法可解决静态法测定液体饱和蒸汽压实验中调整u型管两端液面等高耗时,空气容易倒灌的问题。This paper presented a method to improve the unreasonable design of liquid saturated vapor pressure measurement obtained by static method.The improvement changed the traditional method for measuring the liquid saturated vapor pressure which cannot get the pressure data until both sides of the U-type tube reach the same heigh of liquid level.After marking graduated lines on the two sides of the U-type tube,the liquid saturated vapor pressure can be easily obtained from digital pressure gauge,after the temperature becomes constant and the difference in the height of liquid level is balanced.The time-consuming problem of adjustment of liquid level height on both sides of the U-type tube and the problem of air flow backward could be solved perfectly.It is very helpful to enhance student's understanding of the concept of vapor-liquid equilibrium.国家基础科学人才培养基金项目(J1030415