二氧化钛干凝胶热分解及热处理对表面有机官能团变化的影响

利用X射线衍射(XRD)、差示扫描量热法(DSC)、红外光谱(FTIR)、X射线光电子能谱(XPS)等技术手段研究了溶胶-凝胶(sol-gel)法制备的二氧化钛干凝胶粉末在不同温度下煅烧后表面成分和结构变化,并对不同煅烧温度的粉末样品表面有机官能团的种类及所占的比例进行了探讨。结果表明:二氧化钛干凝胶粉末随着煅烧温度的提高,O-Ti-O结构逐步由复杂的无序网链状结构向有序的晶体结构转变,粉末表面的有机官能团中羧基通过反应产生的螯合物影响二氧化钛晶化;在200~300℃温度范围二氧化钛表面存在大量羟基;300℃左右羧基螯合物分解,在350℃时,憎水碳链官能团已基本除去,在300~350℃,有机官能团加速减少。     

Meldola's Blue Immobilized on a SiO2/SnO2/Phosphate Xerogel,a New Sensor for Determination of Ascorbic Acid in Medicine and Commercial Fruit Juice

A modified carbon paste electrode with SiO₂/SnO₂/Phosphate/Meldola's blue, SSPMelB, was used to study the electrocatalytic oxidation of ascorbic acid by cyclic voltammetry and chronoamperometry. The adsorbed dye mediates ascorbic acid oxidation at an anodic potential of 0.04 V vs. saturated calomel electrode (SCE) at pH 7.0, in 0.5 mol L^?1 solution. The linear range of the sensor is between 4.0×10^?7 and 2.0×10^?3 mol L^?1, with a limit of detection of 4.0×10^?7 mol L^?1. This novel electrode shows good analytical performance for determination of ascorbic acid in medicine and commercial fruit juice.     

Effect of nickel catalyst on physicochemical properties of carbon xerogels as electrode materials for supercapacitor

Carbon xerogels and Ni-doped carbon xerogels prepared by the sol-gel polymerization were examined to reveal the effect of metallic nickel incorporated in carbon matrix on the physicochemical properties of carbon xerogels and their electrochemical performance for supercapacitor electrode in aqueous 6 M KOH solution. As shown by XRD and XPS measurements, the decomposition of nickel precursor in carbon matrix led to the creation of well-crystalline particles of metallic nickel which gave rise to the changes in the morphology, chemical and porous structure of carbon xerogels. Due to the modification of porous structure the surface area increased from 595 m²/g via 632 m²/g up to 660 m²/g for carbon xerogel, 7 wt% and 10 wt% Ni-doped composites, respectively. The enhancement of the surface area occurred along with diminishing the BJH average pore diameter. The value for nickel free xerogel amounted to 11.35 nm, whereas the value of 5.71 nm was measured for 10 wt% Ni xerogel. The changes in the porous and chemical structure created during the formation of carbon-nickel composites as well as the pseudo-capacitive effects arising from the redox reaction of nickel particles present in carbon matrix brought about a significant improvement of electrode capacitance. Electrochemical measurements showed that in comparison with capacitances measured for nickel free electrode (82.1 F/g calculated using the cyclic voltammetry and 88.8 F/g calculated using the galvanostatic charge/discharge method), the respective capacitances for 10 wt% Ni-doped carbon xerogel increased up to 103.0 F/g and 103.4 F/g. These values correspond to 25 and 16% improvement, respectively.