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Selective electrochemical CO2 reduction to CO by a Co(ii) dimer catalyst by metal–ligand cooperativity

Akhter, Sk Samim ; Makhal, Koushik ; Raj, Dev LU ; Raj, Manaswini ; Natarajan M, Thillai ; Mallik, Bhabani S. ; Bhardwaj, Prabhakar ; Kumar, Pankaj ; Nordlander, Ebbe LU and Padhi, Sumanta Kumar LU (2025) In Dalton Transactions 54(45). p.16682-16696
Abstract

An approach to reducing greenhouse gas emissions that shows promise is the electrochemical conversion of CO2 to products with added value. Here, we present [Co(8HQ-Tpy)(H2 O)]2 (PF6 )2 ([Co1]), a cobalt-based molecular electrocatalyst that can convert CO2 to CO in a DMF/H2 O mixture (4.8 : 0.2 v/v) in a selective manner (8HQ-Tpy = 2-([2,2′:6′,2′′-terpyridin]-4′-yl)quinolin-8-ol). At an overpotential of 760 mV, the catalyst shows a TOFmax of 2575 s−1 and a high Faradaic efficiency of 94 ± 2%. The CO2 reduction follows both ECEC and EECC-type routes, involving stepwise proton and electron transfer, according to a mechanistic... (More)

An approach to reducing greenhouse gas emissions that shows promise is the electrochemical conversion of CO2 to products with added value. Here, we present [Co(8HQ-Tpy)(H2 O)]2 (PF6 )2 ([Co1]), a cobalt-based molecular electrocatalyst that can convert CO2 to CO in a DMF/H2 O mixture (4.8 : 0.2 v/v) in a selective manner (8HQ-Tpy = 2-([2,2′:6′,2′′-terpyridin]-4′-yl)quinolin-8-ol). At an overpotential of 760 mV, the catalyst shows a TOFmax of 2575 s−1 and a high Faradaic efficiency of 94 ± 2%. The CO2 reduction follows both ECEC and EECC-type routes, involving stepwise proton and electron transfer, according to a mechanistic investigation that combines DFT calculations, infrared spectroelectrochemistry (IR-SEC), and kinetic isotope effect (KIE) observations. Sequential protonation and CO2 activation are made possible by the reduction of a hexa- to penta-coordinate Co centre. According to DFT studies, protonation at the ligand O− site, which takes place before CO2 coordination and favours an EECC pathway, becomes thermodynamically favourable following reduction. Both deprotonated and protonated CO2 -derived intermediates are captured by IR-SEC measurements, and proton transfer is not rate-limiting as the KIE is low (kH /kD = 1.17). When taken as a whole, these results offer a comprehensive mechanistic understanding of CO2 -to-CO conversion as well as design guidelines for creating advanced molecular electrocatalysts for carbon capture and utilization.

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author
; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Dalton Transactions
volume
54
issue
45
pages
15 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:105022266329
  • pmid:41200865
ISSN
1477-9226
DOI
10.1039/d5dt02003d
language
English
LU publication?
yes
id
71b70e23-87b5-48e7-b0bd-da48093c12f3
date added to LUP
2026-01-30 15:52:41
date last changed
2026-01-30 15:52:52
@article{71b70e23-87b5-48e7-b0bd-da48093c12f3,
  abstract     = {{<p>An approach to reducing greenhouse gas emissions that shows promise is the electrochemical conversion of CO<sub>2</sub> to products with added value. Here, we present [Co(8HQ-Tpy)(H<sub>2</sub> O)]<sub>2</sub> (PF<sub>6</sub> )<sub>2</sub> ([Co1]), a cobalt-based molecular electrocatalyst that can convert CO<sub>2</sub> to CO in a DMF/H<sub>2</sub> O mixture (4.8 : 0.2 v/v) in a selective manner (8HQ-Tpy = 2-([2,2′:6′,2′′-terpyridin]-4′-yl)quinolin-8-ol). At an overpotential of 760 mV, the catalyst shows a TOF<sub>max</sub> of 2575 s<sup>−1</sup> and a high Faradaic efficiency of 94 ± 2%. The CO<sub>2</sub> reduction follows both ECEC and EECC-type routes, involving stepwise proton and electron transfer, according to a mechanistic investigation that combines DFT calculations, infrared spectroelectrochemistry (IR-SEC), and kinetic isotope effect (KIE) observations. Sequential protonation and CO<sub>2</sub> activation are made possible by the reduction of a hexa- to penta-coordinate Co centre. According to DFT studies, protonation at the ligand O<sup>−</sup> site, which takes place before CO<sub>2</sub> coordination and favours an EECC pathway, becomes thermodynamically favourable following reduction. Both deprotonated and protonated CO<sub>2</sub> -derived intermediates are captured by IR-SEC measurements, and proton transfer is not rate-limiting as the KIE is low (k<sub>H</sub> /k<sub>D</sub> = 1.17). When taken as a whole, these results offer a comprehensive mechanistic understanding of CO<sub>2</sub> -to-CO conversion as well as design guidelines for creating advanced molecular electrocatalysts for carbon capture and utilization.</p>}},
  author       = {{Akhter, Sk Samim and Makhal, Koushik and Raj, Dev and Raj, Manaswini and Natarajan M, Thillai and Mallik, Bhabani S. and Bhardwaj, Prabhakar and Kumar, Pankaj and Nordlander, Ebbe and Padhi, Sumanta Kumar}},
  issn         = {{1477-9226}},
  language     = {{eng}},
  number       = {{45}},
  pages        = {{16682--16696}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Dalton Transactions}},
  title        = {{Selective electrochemical CO<sub>2</sub> reduction to CO by a Co(ii) dimer catalyst by metal–ligand cooperativity}},
  url          = {{http://dx.doi.org/10.1039/d5dt02003d}},
  doi          = {{10.1039/d5dt02003d}},
  volume       = {{54}},
  year         = {{2025}},
}