# Effect of urea as a chaotropic agent on self-association of organic molecules in aqueous flow batteries

## TL;DR

This study explores how urea affects the aggregation of molecules used in aqueous flow batteries, finding that while urea disrupts molecular interactions, it does not significantly improve battery performance.

## Contribution

The paper reveals that urea partially disrupts aggregation but does not enhance electrochemical performance of organic molecules in flow batteries.

## Key findings

- Urea disrupts π–π stacking and reduces concentration-dependent shifts in NMR.
- Electrochemical measurements showed only partial improvement in molecular interactions.
- Urea did not lead to improved capacity utilization in flow battery testing.

## Abstract

This paper investigates the effect of urea, a widely used denaturing co-solute, on the aggregation of promising candidates for aqueous organic flow batteries, specifically 9,10-anthraquinone-2,7-disulfonic acid (AQDS) and naphthalene diimide derivatives (NDIs). These molecules undergo aggregation through π–π interactions of their aromatic cores. We evaluated how urea influences molecular interactions and electrochemical behavior of these molecules by nuclear magnetic resonance (NMR), cyclic voltammetry (CV), rotating disk electrode (RDE), and flow battery testing. While NMR confirmed that urea effectively disrupts π–π stacking and reduces the concentration-dependent shifts and peak broadening, electrochemical measurements showed that this effect is only partial. These results highlight the difference between molecular-level disruption of aggregation and limited improvements in electrochemical performance.

Urea reduced the aggregation of redox active molecules, but did not lead to improved capacity utilization.