posted on 2023-01-06, 18:08authored byCharles
Tai-Chieh Wan, Akram Ismail, Alexander H. Quinn, Yet-Ming Chiang, Fikile R. Brushett
Redox
flow batteries (RFBs) are a promising electrochemical technology
for the efficient and reliable delivery of electricity, providing
opportunities to integrate intermittent renewable resources and to
support unreliable and/or aging grid infrastructure. Within the RFB,
porous carbonaceous electrodes facilitate the electrochemical reactions,
distribute the flowing electrolyte, and conduct electrons. Understanding
electrode reaction kinetics is crucial for improving RFB performance
and lowering costs. However, assessing reaction kinetics on porous
electrodes is challenging as their complex structure frustrates canonical
electroanalytical techniques used to quantify performance descriptors.
Here, we outline a strategy to estimate electron transfer kinetics
on planar electrode materials of similar surface chemistry to those
used in RFBs. First, we describe a bottom-up synthetic process to
produce flat, dense carbon films to enable the evaluation of electron
transfer kinetics using traditional electrochemical approaches. Next,
we characterize the physicochemical properties of the films using
a suite of spectroscopic methods, confirming that their surface characteristics
align with those of widely used porous electrodes. Last, we study
the electrochemical performance of the films in a custom-designed
cell architecture, extracting intrinsic heterogeneous kinetic rate
constants for two iron-based redox couples in aqueous electrolytes
using standard electrochemical methods (i.e., cyclic voltammetry,
electrochemical impedance, and spectroscopy). We anticipate that the
synthetic methods and experimental protocols described here are applicable
to a range of electrocatalysts and redox couples.