Abstract—

Electroconvection is the principal mechanism that allows markedly increasing the rate of ion transfer through ion-exchange membranes in intensive current regimes. In this work, we investigated the possibility of intensifying electroconvection in solution near heterogeneous MA-41 anion-exchange membrane (Shchekinoazot production) by the modifying of its surface. The use of weakly crosslinked ion-exchange resin (MA-41P) in the course of the membrane manufacturing, with subsequent chemical modification of its surface (MA-41PM), is shown to make it possible to increase the limiting current density almost twice. The value of the reduced potential drop (after subtracting the ohmic contribution), at which significant generation of H⁺ and OH^– ions begins, is shifted from 0.8 V in the case of MA-41 to 1.7 V in the case of MA-41PM. The current density related to the onset of water splitting is equal to 0.9\(i_{{{\text{lim}}}}^{{{\text{Lev}}}},\) in the case of MA-41; 2\(i_{{{\text{lim}}}}^{{{\text{Lev}}}},\) in the case of MA-41PM (where \(i_{{{\text{lim}}}}^{{{\text{Lev}}}}\) is the theoretical value of the limiting current density). The special feature of the modified membrane behavior is the presence of a range of potential drop (between 50 and 80 mV in the reduced scale), in which the system with the MA-41PM has negative differential resistance: in this range, the potential drop decreases when the current density increases. This behavior occurs when measuring quasi-stationary I–V curves; correspondingly, in the chronopotentiogram there is a time interval, where the potential drop decreases with time. The electroconvection is intensified near a modified membrane due to a higher fraction of conductive areas on the surface of the modified membrane and the redistribution of these areas via formation of their agglomerates in the centers of the cells formed by the reinforcing mesh. Mathematical modeling shows the concentration polarization of the modified membrane being less than that of the pristine one. Meanwhile, the structure of electroconvective vortices is optimized: the vortices near the modified membrane are larger; they do not extinguish each other, unlike the case of MA-41.

中文翻译：

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阴离子交换膜的表面改性对其表面电对流强度的影响

摘要—

电对流是在强电流状态下可以显着提高通过离子交换膜的离子转移速率的主要机制。在这项工作中，我们研究了通过修饰其表面来增强异质MA-41阴离子交换膜附近溶液中电对流的可能性（Shchekinoazot生产）。膜制造过程中使用弱交联的离子交换树脂（MA-41P），并对其表面进行化学修饰（MA-41PM），显示出可以将极限电流密度几乎提高两倍。还原电势降的值（减去欧姆贡献之后），在该H的显著产生⁺和OH ^-离子开始，从MA-41的0.8 V切换到MA-41PM的1.7V。在MA-41的情况下，与水分解开始有关的电流密度等于0.9 \（i _ {{{\ text {lim}}}} ^ {{{{\ text {Lev}}}}，\） ; 2 \（i _ {{{\ text {lim}} ^ {{{\ text {Lev}}}}，\）在MA-41PM的情况下（其中\（i _ {{{\ text {lim} }}} ^ {{{{\ text {Lev}}}}} \）是极限电流密度的理论值。改进的膜性能的特点是存在一定范围的电势降（在缩小范围内为50至80 mV），其中MA-41PM的系统具有负差分电阻：在此范围内，电势降当电流密度增加时，电流减小。测量准静态IV时会发生这种现象曲线 相应地，在计时电位图中有一个时间间隔，其中电位降随时间减小。由于修饰膜表面上较高的导电区域比例，并且通过在增强网格形成的单元中心形成它们的团聚体，这些区域的重新分布，使得在修饰膜附近的电对流增强了。数学模型表明改性膜的浓度极化小于原始膜的浓度极化。同时，优化了对流涡流的结构：改性膜附近的涡流较大；与MA-41不同，它们不会相互熄灭。