Utilization of Electropolymerized Films of Cobalt Porphyrin for the Reduction of Carbon Dioxide in Aqueous Media. Issue 22 (27th October 2016)

• Record Type: Journal Article
• Authors: Pander, James E.; Fogg, Alex; Bocarsly, Andrew B.
• Is Part Of: ChemCatChem. Volume 8:Issue 22(2016)
• Page Start: 3536
• Page End: 3545
• Publication Date: 2016-10-27
• Subjects: cobalt -- electrochemistry -- macrocycles -- polymers -- reduction; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201600875
• Languages: English
• ISSNs: 1867-3880

Abstract

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 13 CO2 reactant led exclusively to 13 CO as the product. Polymeric films of the unmetalated porphyrin did not demonstrate catalysis for CO2 reduction. UV/Vis spectroelectrochemical experiments indicate that the parent Co II complex is reduced to Co I 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 Co II moiety to Co I, 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. Abstract : The reduction of carbon dioxide : A facile electropolymerization process is utilized to prepare electrodes modified with thin films of cobalt protoporphyrin IX. These thin films exhibit 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 of −5.9. A new metric for the evaluation of electrocatalysts, the catalytic efficiency, is proposed.