Utilization of Electropolymerized Films of Cobalt Porphyrin for the Reduction of Carbon Dioxide in Aqueous Media

James E. Pander, Alex Fogg, Andrew Bruce Bocarsly

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

A facile electropolymerization process was utilized to prepare electrodes modified with thin films of cobalt protoporphyrin IX. These thin films exhibited a high Faradaic efficiency (84±2 %) for the reduction of CO2 to CO in aqueous solutions near neutral pH with 450 mV of overpotential and a turnover frequency at zero overpotential (log(TOF0)) of −5.9. The production of CO was stable over several hours at these modest potentials. The use of a 13CO2 reactant led exclusively to 13CO as the product. Polymeric films of the unmetalated porphyrin did not demonstrate catalysis for CO2 reduction. UV/Vis spectroelectrochemical experiments indicate that the parent CoII complex is reduced to CoI at the electrode surface before interaction with CO2. It is proposed that the rate-determining step in the reduction of CO2 is the initial reduction of the CoII moiety to CoI, which binds CO2 and then undergoes a proton-coupled electron transfer and a loss of water to form CO. Additionally, a new metric for the evaluation of electrocatalysts, the catalytic efficiency, is proposed. The catalytic efficiency is the ratio of the power stored to power consumed for a given electrochemical reaction and can be used to describe both the kinetics and overpotential considerations of a given system.

Original languageEnglish (US)
Pages (from-to)3536-3545
Number of pages10
JournalChemCatChem
Volume8
Issue number22
DOIs
StatePublished - Nov 22 2016

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Keywords

  • cobalt
  • electrochemistry
  • macrocycles
  • polymers
  • reduction

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