Hydrogen bonding assisted OH- transport under low humidity for rapid start-up in AEMFCs

The apparent degradation of alkaline fuel cells performance at reduced relative humidity (RH) drives the interest in further improving anion exchange membranes (AEMs) functionalities and/or developing alternative AEMs. Herein, we report an AEM with urea-based structure that exhibits excellent low humidity performance. Micro-structure analysis and molecular dynamics simulation show that hydrogen bonding between urea-based structures enhances the self-assembly ability of quaternary ammoniums groups and expanded OH- conduction pathway. Besides, the hydrogen bond network formed by urea-urea group and urea-water group endows the AEMs with excellent water retention ability, thereby decreasing the dependence of OH- conduction on RH. The resultant AEM shows outstanding fuel cell power density (210 mW cm(-2)) under special operating conditions like 40 ? and 50% RH, which exhibits 2.5 times better than hydrogen bonding-free AEM. This work simulates the real working state of the fuel cells and provides significant guidance for rapid start-up in anion exchange membrane fuel cells (AEMFCs).

Automated summary

This study reports an AEM with a urea-based structure that exhibits excellent performance under low humidity conditions. Micro-structure analysis and molecular dynamics simulation show that hydrogen bonding between urea-based structures enhances the self-assembly ability and OH- conduction pathway of the AEM. The hydrogen bond network formed by urea-urea and urea-water groups endows the AEM with excellent water retention ability, reducing the dependence of OH- conduction on humidity. The research provides significant guidance for rapid start-up in AEM fuel cells.