Renewable Hydride Donors for the Catalytic Reduction of CO 2 : A Thermodynamic and Kinetic Study
Increasing atmospheric CO2 concentration and dwindling fossil fuel supply necessitate the search for efficient methods for CO2 conversion to fuels. Assorted studies have shown pyridine and its derivatives capable of (photo)electrochemically reducing CO2 to methanol, and some mechanistic interpretations have been proposed. Here, we analyze the thermodynamic and kinetic aspects of the efficacy of pyridines as hydride-donating catalytic reagents that transfer hydrides via their dihydropyridinic form. We investigate both the effects of functionalizing pyridinic derivatives with electron-donating and electron-withdrawing groups on hydride-transfer catalyst strength, assessed via their hydricity (thermodynamic ability) and nucleophilicity (kinetic ability), and catalyst recyclability, assessed via their reduction potential. We find that pyridines substituted with electron-donating groups have stronger hydride-donating ability (having lower hydricity and larger nucleophilicity values), but are less efficiently recycled (having more negative reduction potentials). In contrast, pyridines substituted with electron-withdrawing groups are more efficiently recycled, but are weaker hydride donors. Functional group modification favorably tunes hydride strength or efficiency, but not both. We attribute this problematic coupling between the strength and recyclability of pyridinic hydrides to their aromatic nature and suggest several avenues for overcoming this difficulty.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- National Science Foundation (NSF)
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1482501
- Report Number(s):
- NREL/JA-5K00-72804
- Journal Information:
- Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry, Vol. 122, Issue 44; ISSN 1520-6106
- Publisher:
- American Chemical Society
- Country of Publication:
- United States
- Language:
- English
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