An Iron Pyridyl-Carbene Catalyst for Low Overpotential CO2 reduction to CO: Mechanistic Comparisons with the Ruthenium Analogue and Photochemical Promotion

02 March 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Electrocatalysts for CO2 reduction based on first row transition metal ions have attracted attention as abundant and affordable candidates for energy conversion applications. We hypothesized that a successful strategy in ruthenium electrocatalyst design, featuring two chelating ligands that can be individually tuned to adjust the overpotential and catalytic activity, could be equally applicable in the analogous iron complexes. New iron complexes supported by a redox-active 2,2':6',2''-terpyridine (tpy) ligand and strong trans effect pyridyl- N-heterocyclic carbene ligand (1-methyl-benzimidazol-2-ylidene-3-(2-pyridine)) were synthesized, and these isostructural analogues to leading ruthenium catalysts were also found to be active CO2 reduction electrocatalysts. Electrochemical and computational studies reveal completely distinct mechanisms for the iron and ruthenium complexes, with hemilability in the iron system enabling electrocatalysis at overpotentials as low as 150 mV (ca. 500 mV lower than the ruthenium analogue). Cyclic voltammetry studies elucidated the mechanism of the net 4e–/2H+ process that occurs within the single reductive feature, with an iron solvento complex undergoing reduction, CO2 activation, and further reduction to an iron carbonyl. The mechanistic insight guided development of photoelectrocatalytic conditions under a continuous flow of CO2 that exhibited improved performance, with Faradaic efficiency up to 99%.

Keywords

CO2 reduction
electrocatalysis
N-heterocyclic carbene ligand
iron

Supplementary materials

Title
Description
Actions
Title
FeBimpy Manuscript Submission
Description
Actions
Title
20200302 FeBimpy SI
Description
Actions
Title
CIF C Fe MeCN2+
Description
Actions
Title
CIF N Fe CO2+
Description
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.