Understanding current amplification by quaternary ammonium polybromides droplets on Pt ultramicroelectrode

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>In this article, we report that electrochemically generated quaternary ammonium polybromide (QBr<SUB>2n+1</SUB>) droplets can act not only as electrochemical reactors for the electro-oxidation of Br<SUP>−</SUP>, but also as tiny reductants for Br<SUB>2</SUB> dissolved in an aqueous phase. We suggest two different theoretic models: <I>Cloud</I> and <I>Droplet</I>. In the <I>Cloud</I> model, we consider a cloud composed of small droplets located in the vicinity of a Pt ultramicroelectrode (UME). The positive feedback loop of the redox reaction is derived in the gap between the <I>Cloud</I> and the Pt UME, which leads to catalytic current enhancement, like the positive feedback mode of scanning electrochemical microscopy (SECM). In the <I>Droplet</I> model, a droplet adsorbed on the center of a Pt UME drives the catalytic feedback loop of the redox reaction. Next, we adopted the two theoretical models to explain the current amplification by QBr<SUB>2n+1</SUB> observed in our experimental systems. In the early potential region for electro-oxidation of Br<SUP>−</SUP>, we found the QBr<SUB>2n+1</SUB> droplets-<I>Cloud</I> model was a more reliable scenario for the catalytic current amplification. As the potential became more positively biased, stochastic collisions of QBr<SUB>2n+1</SUB> droplets occurred on the Pt UME, and in this stage, we determined that the QBr<SUB>2n+1</SUB>-<I>Droplet</I> model was the main catalytic mechanism for Br<SUP>−</SUP> electro-oxidation in the presence of QBr in the solution.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>