Chemical Engineering and Industrial Chemistry

Synthesis and Characterization of Dense Carbon Films as Model Surfaces to Estimate Electron Transfer Kinetics on Redox Flow Battery Electrodes

Authors

  • Charles Wan Joint Center for Energy Storage Research & Massachusetts Institute of Technology ,
  • Akram Ismail University of Rochester ,
  • Alexander Quinn Massachusetts Institute of Technology ,
  • Yet-Ming Chiang Joint Center for Energy Storage Research & Massachusetts Institute of Technology ,
  • Fikile Brushett Joint Center for Energy Storage Research & Massachusetts Institute of Technology

Abstract

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 evaluation of electron transfer kinetics using traditional electrochemical approaches. Next, we characterize 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 spectroscopy). We anticipate that the synthetic methods and experimental protocols described here are applicable to a range of electrocatalysts and redox couples.

Content

Thumbnail image of Wan_et_al_Dense_Carbon_Film_Manuscript_ChemRxiv_final.pdf

Supplementary material

Thumbnail image of Wan_et_al_Dense_Carbon_Film_SI_ChemRxiv_final.pdf
Supporting Information - Synthesis and Characterization of Dense Carbon Films as Model Surfaces to Estimate Electron Transfer Kinetics on Redox Flow Battery Electrodes
Supporting Information for "Synthesis and Characterization of Dense Carbon Films as Model Surfaces to Estimate Electron Transfer Kinetics on Redox Flow Battery Electrodes" contains surface analysis of the dense films through images of the surface and atomic force microscopy, full Raman spectroscopy of the dense films and commercial electrodes, deconvoluted high resolution X-ray photoelectron spectroscopy of electrode materials, analysis to determine the regime of reversibility in cyclic voltammetry experiments, and a background scan of dense films compared to the iron ferricyanide redox couple.