Earth-Abundant Molecular Catalyst Systems for the Reduction of Dioxygen and Carbon Dioxide

Charles Machan^a, Emma Cook^a, Amelia Reid^a, Connor Koellner^a, Megan Moberg^a

^aDepartment of Chemistry, University of Virginia

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)

#HOMHET - Bridging The Gap Between Homogeneous and Heterogeneous (Photo)-Electrocatalysis

Torremolinos, Spain, 2023 October 16th - 20th

Organizers: Idan Hod, Elena Mas Marzá and Menny Shalom

Invited Speaker, Charles Machan, presentation 053
DOI: https://doi.org/10.29363/nanoge.matsus.2023.053
Publication date: 18th July 2023

The steady increase in anthropogenic carbon dioxide (CO₂) emissions and atmospheric concentration continues to generate interest in using CO₂ as a precursor for fuels and commodity chemicals. The conversion of CO₂ has the dual benefit of addressing its associated negative environmental effects and the diminishing supply of petrochemical feedstocks. Likewise, the electrocatalytic reduction of dioxygen (O₂), has relevance to the development of more efficient fuel cells and chemical oxidations, as well as our understanding of how bioinorganic systems convert energy-rich molecules during respiration. At the heart of efficient reductive transformations are proton-coupled electron transfer (PCET) reactions, where electrons and protons move in a concerted way to mitigate kinetic and thermodynamic penalties. Mechanistic understanding of these reactions can inform the design of optimized catalyst structures with improved activity and selectivity for specific products. Molecular systems are well-positioned to provide a better understanding of these reactions because of the relative fidelity with which they can be characterized, as well as the possibility for systematic testing of structure-function relationships through iterative molecular design. In addition to developing new Co-, Fe-, Mn-, and Cr-based molecular electrocatalysts for these reactions, we are exploring the use of redox mediators and flow-based electrochemical reactors to understand how these reactions can be scaled relative to comparable heterogeneous systems.

References:

[1] Koellner, C.A.; Reid, A.G.; Machan, C.W.# “Co-electrocatalytic CO2 Reduction Mediated by a Dibenzophosphole Oxide and a Chromium Complex” Chem. Commun. 2023 Advance Article DOI: 10.1039/D3CC00166K.

[2] Reid, A.G.; Moberg, M.E.; Koellner, C.A.; Moreno, J.J.; Hooe, S.L.; Baugh, K.R.; Dickie, D.A.; Machan, C.W.# “Comparisons of bpy and phen Ligand Backbones in Cr-Mediated (Co-)Electrocatalytic CO2 Reduction” Organometallics 2023, 42, 1139–1148.

[3] Reid, A.G.; Machan, C.W.# “Redox Mediators in Homogeneous Co-electrocatalysis” J. Am. Chem. Soc. 2023, 145, 2013–2027.

[4] Reid, A.G.*; Hooe, S.L.*; Moreno, J.J.; Dickie, D.A.; Machan, C.W.# “Homogeneous Electrocatalytic Reduction of CO2 by a CrN3O Complex: Electronic Coupling with Redox-Active Terpyridine Fragment Favors Selectivity for CO” Inorg. Chem. 2022, 61, 16963–16970.

[5] Cook, E.N.; Machan, C.W.# “Homogeneous Catalysis of Dioxygen Reduction by Molecular Mn Complexes” Chem. Commun. 2022, 58, 11746–11761.

[6] Reid, A.G.; Moreno, J.J.; Hooe, S.L.; Baugh, K.R.; Thomas, I.H.; Dickie, D.A.; Machan, C.W.# “Inverse Potential Scaling in Co-Electrocatalytic Activity for CO2 Reduction Through Redox Mediator Tuning and Catalyst Design” Chem. Sci. 2022, 13, 9595–9606

[7] Cook, E.N.; Dickie, D.A.; Machan, C.W.# “Catalytic Reduction of Dioxygen to Water by a Bioinspired Non-Heme Iron Complex via a 2+2 Mechanism” J. Am. Chem. Soc. 2021, 143, 16411–16418.

Acknowledgements:

DOE Basic Energy Sciences, Catalysis, DE-SC0022219; NSF MPS Chemistry Catalysis, CHE-2102156; University of Virginia, Rivanna High-Performance Cluster

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