铂-氢钨青铜电极的制备及对氢氧化的电催化

采用电化学还原法在表面改性的碳布上,通过改变催化剂沉积顺序及氢钨青铜沉积时间制备铂-氢钨青铜复合催化剂,所得电极作为质子交换膜燃料电池(PEMFC)阳极。利用X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、循环伏安(CV)及单电池极化性能测试研究了催化剂的组成、沉积量、分散性及其对氢氧化的电催化活性。实验结果表明,氢钨青铜沉积时间及催化剂沉积顺序对电极催化性能有显著影响,当氢钨青铜沉积时间为10 min,先沉积氢钨青铜、后沉积铂所得Pt/HxWO3电极对氢氧化具有最佳的催化活性。适量的氢钨青铜才能与铂形成较好的协同催化效应。     

Electrochemical Reduction of Arylxenon Tetrafluoroborates

Reduction potentials of arylxenon(II) tetrafluoroborates have been measured by cyclic voltammetry method on platinum disc and ultramicro electrodes. The electrochemical properties of the arylxenon(II) tetrafluoroborates are quite different to those of corresponding arylperfluoralkyliodine(III) salts.     

石墨烯/银复合薄膜的制备及表征

采用静电自组装技术,通过交替沉积聚(二烯丙基二甲基氯化铵)(PDDA)(或硝酸银)和氧化石墨烯,制备氧化石墨烯/PDDA薄膜和氧化石墨烯/硝酸银复合薄膜。然后在600℃下通入氩气和氢气进行气氛还原得到石墨烯薄膜和石墨烯/银复合薄膜。采用AFM、SEM、XPS、UV-Vis以及四探针电阻仪等对薄膜结构及性质进行表征。结果表明,通过静电自组装法可以获得生长均匀的薄膜。对比于相同自组装次数的石墨烯薄膜,石墨烯/银复合薄膜具有更好的透光性和更低的薄膜方块电阻。在λ=500 nm时,四层石墨烯/银复合薄膜的透过率为85%左右,而石墨烯薄膜的透过率为72%左右;石墨烯薄膜的方阻为161.39 kΩ.□-1,而石墨烯/银复合薄膜的方阻为99.11 kΩ.□-1。     

磁性碳包铁纳米粒子在重金属元素检测分离富集中的应用

以氩电弧等离子体法制备的碳包铁纳米粒子为固相萃取材料,采用等离子体原子发射光谱法(ICP-AES)系统研究了该材料对Cr、Ni、Cd、Pb离子的吸附性能,并确定了最佳吸附和洗脱条件。实验结果表明:当pH值为8.0～9.0时,分析物均可被碳包铁纳米粒子定量吸附;采用酸性溶液(pH=1.0～2.0)可将吸附在碳包铁纳米粒子上的金属离子完全脱附。该法对Cr、Ni、Cd、Pb的检出限分别为3.6、4.1、1.1、9.8μg/L,Cr、Ni、Cd的线性范围为1～500μg.L-1,Pb的线性范围为10～1 000μg.L-1,线性相关系数均大于0.999。方法用于自来水中Cr、Ni、Cd、Pb离子的测定,回收率可达到93%～105%;碳包铁纳米粒子对Cr、Ni、Cd、Pb离子的吸附量分别为3.6、4.8、6.3、2.1 mg/g。     

Accurate determination of extra-column band broadening using peak summation

The present contribution addresses the problem of the accurate determination of the extra-column band-broadening dispersion by applying the method of moments (MOM) on pulse response experiments. The MOM provides the only mathematically rigorous way to determine the variance of a pulse response, but suffers from the fact that the obtained variance values usually depend very strongly and unpredictably on the selected integration boundaries. In the present study, it is investigated whether the MOM cannot be made more accurate by repeating the pulse response experiment a number of times, then add all measured peaks (after retention time alignment) and subsequently perform the integration on this summed peak. Testing this approach for a number of different integration boundary detection methods consistently more accurate results are obtained than when the different repeat response pulses are integrated individually and the variances are averaged afterwards. It was also found that adding five repeats already leads to a significant improvement of the variance estimate, whereas the addition of 10-20 repeats is needed before the variance estimate converges to a steady value.