Modulation of ionic current rectification direction for biomimetic aluminum oxide membrane by surface modification

A biomimetic aluminum oxide membrane having asymmetric channels with a minimum diameter of 20 nm, a maximum diameter of 80 nm, and a length of 5 mu m was prepared using square pulse anodization. The membrane effectively permitted transfer of anions only and showed an ionic current rectification characteristic with a rectification ratio of 2.4. After the sulfonic acid group was introduced by surface modification, the membrane effectively permitted transfer of cations only and showed a rectification ratio of 2.7. This modulation of the ionic current rectification direction was consistent with the theoretical prediction through the numerical analysis of 2D models. These findings present a convenient method to control ion transport for the ion exchange membrane. (C) 2022 Author(s).

Automated summary

A biomimetic aluminum oxide membrane with asymmetric channels was prepared using square pulse anodization. The membrane exhibited controllable ionic current rectification characteristics and allowed for selective transport of either anions or cations through surface modification. These findings have important implications for the design and application of ion exchange membranes.