Abstract:

Optical  fluorescencemicroscopy  is  shown  to  enable  both  highspatial  and  temporal  resolution  of  redox-dependent  fluorescencein  flowing  electrolytes.  We  report  the  use  of  fluorescence  micro-scopy coupled with electrochemistry to directly observe the reac-tion and transport of redox-active quinones within porous carbonelectrodesin  operando.  We  observe  surprising  electrolyte  chan-neling features within several porous electrodes, leading to spatiallydistinguishable  advection-dominated  and  diffusion-dominated  re-gions. These results challenge the common assumption that trans-port in porous electrodes can be approximated by a homogeneousDarcy-like permeability, particularly at the length scales relevant tomany  electrochemical  systems  such  as  redox  flow  batteries.  Thiswork  presents  a  new  platform  to  provide  highly  resolved  spatialand   temporal   insight   into   electrolyte   reactions   and   transportbehavior within porous electrodes.