Electrochemical synthesis of a crystalline film of tetrabutylammonium bromide

An anodic oxidation of aqueous Br− ions on platinum substrate in the presence of tetrabutylammonium (Bu4N+) ions leads to the formation of Br3−. This accompanies the self-assembly of Bu4N+ cations to the electrogenerated Br3− anions being accumulated near the electrode surface. The deposited Br3− anions can be replaced with Br− in solution by ion exchange, resulting in a thin film of Bu4NBr salt with high crystallinity and low electrical conductivity.