复合聚合物修饰的粉末微电极及其对亚硝酸根还原的催化

本论文简述用Nafion_Os(bpy) 3 2 + /PVP复合膜修饰的乙炔黑粉末微电极 ,以亚硝酸根还原为模型反应 ,实现从复合修饰及扩大电极比表面两方面改善电极性能的思路 .结果表明 ,它同时显示Nafion_Os(bpy) 3 2 + /PVP修饰电极对NO2 -及NO+ 双重富集并再生活性粒子NO+ 、防止中继体流失、加速膜中中继体传输、改变反应途径等复合修饰电极的多种功能以及粉末微电极的高比表面、高液相传质速度以及薄层效应的特性 .与平面修饰电极及裸粉末微电极相比 ,它明显提高了酸性溶液中亚硝酸根还原的可逆性、呈数量级地提高稳态极限电流密度以及NO2 -的检测指标 .

Powder Microelectrode Modified with Nafion-Os(bpy)32+ and PVP Composite and Its Catalysis for NO2- Reduction

The modified powder microelectrode was prepared by etching a Pt (0.1 mm diameter) disk microelectrode and filling in thus formed cavity with Nation_Os(bpy) 3 2+ /PVP composite modified carbon powder. The composite modified powder microelectrode showed cyclic voltammetric behaviors changing with the mole ratio (denoted X) of SO 3 - to Os(bpy) 3 2+ in Nafion. When X=3, a single pair of current peaks appeared near 0.6V (vs. SCE) due to Os(bpy) 3 2+/3+ redox couple. In contrast, for X=20, a pair of additional current peaks occurred near 0.4V. Both X=3 and X=20 modified powder microelectrodes strongly catalyzed the first electron reduction of nitrite in 0.5 mol/L H 2SO 4. The catalysis was so effective that the steady state polarisation curve showed essentially reversible characteristics with a plateau current density 2.18 mA/cm 2 and half_wave potentials near 0.55 V. While the electrode with X=3 could catalyze nitrite reduction only to the first electron transfer, the modified powder microelectrode with X=20 could catalyze the second electron transfer, resulting in an additional current wave starting near 0.4 V with a plateau current twice the first one. The plateau current densities obtained with the composite modified powder microelectrodes were much larger than those obtainable with flat electrodes (with or without modification), verifying the idea of advantageous combination of the composite modification and the porous electrode technique. The composite modified powder microelectrodes showed high performance in nitrite detection: sensitivity 814 mAL/cm 2 mole, linearity 10 _6 ～0.25 mol/L, lower detection limit 10 _6 mol/L; no interference from 0.1 mol/L ascobic acid, Fe 3+ ,Fe 2+ ,Mg 2+ ,K +,NH 4+ ,Cl -,NO - 3 and PO 3_ 4.