Department of Electrical and Computer Engineering, Seoul National University, Seoul, 08826, Republic of Korea.
Department of Chemical and Biological engineering, Jeju National University, 63243, Republic of Korea.
Lab Chip. 2021 Jun 1;21(11):2153-2162. doi: 10.1039/d1lc00064k.
Overlimiting current through a perm-selective membrane has been actively researched not only for the fundamental advancement of electrokinetics but also for energy/environmental applications such as electrodialysis, fuel cells, etc. In particular, various strategies were reported for the enhancement of overlimiting current because these applications demand efficient mass transport through the membrane. In this work, we presented in operando visualization and rigorous numerical study for the overlimiting current density enhancement using a pulsed electric field which is one of the most cost-effective parameters to be externally controlled. We clearly demonstrated that the current density had a peak value as a function of the pulse frequency and would suggest its correlation to a concentration profile and diffusion relaxation time ([small tau, Greek, tilde]diff). As the pulse frequency was chosen which is similar to ([small tau, Greek, tilde]diff)-1, the concentration profiles (i.e. established current paths) were maintained even in off-state due to remnant current paths helping the fast ion transportation. The fundamental evidence presented in this work would provide a strategical design of a perm-selective membrane system for a higher mass transportation efficiency.
过限电流通过选择透过性膜的研究不仅对电动学的基础发展具有重要意义，而且在电渗析、燃料电池等能源/环境应用中也具有重要意义。特别是，为了提高过限电流，已经报道了各种策略，因为这些应用需要通过膜进行有效的传质。在这项工作中，我们使用脉冲电场进行了操作中的可视化和严格的数值研究，以提高过限电流密度，这是最具成本效益的可外部控制参数之一。我们清楚地表明，电流密度随脉冲频率呈峰值变化，并建议其与浓度分布和扩散弛豫时间([small tau, Greek, tilde]diff)相关。当选择与([small tau, Greek, tilde]diff)-1 相似的脉冲频率时，由于残留的电流路径有助于快速离子传输，即使在关闭状态下，浓度分布（即建立的电流路径）也能保持。这项工作提出的基本证据将为具有更高传质效率的选择透过性膜系统的战略设计提供依据。
