Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide This report describes an investigation of the role of H 2 O and N, N -dimethylformamide (DMF) as solvents in the electrochemical oxidation of oxalate (C 2 O 4 2– ). In H 2 O/0.1 M Na 2 SO 4, the 2e – oxidation of C 2 O 4 2– yields two CO 2 molecules via a classical ECE mechanism, resulting in a single oxidation wave at 1.2 V vs Ag/AgCl. In contrast, two distinct oxidation waves are observed in DMF/0.1 M TBAP at ∼0.1 V and ∼0.7 V vs Ag/AgCl. The second wave at more positive potentials in DMF was first assigned by Maran and co-workers to the oxidation of the adduct C 2 O 4 2– ·CO 2 formed from generation of CO 2 during the first wave. Electronic interaction of C 2 O 4 2– and CO 2 stabilizes C 2 O 4 2–, making it more difficult to oxidize than free C 2 O 4 2– . Herein we present cyclic voltammetry (CV), finite difference (FD) simulations, Raman spectroscopy, and ab initio molecular dynamics (AIMD) simulations to determine the thermodynamics and kinetics of C 2 O 4 2– ·CO 2 formation as well as the adduct structure. FD simulations of the voltammetric data provide approximate thermodynamic and kinetic parameters for C 2 O 4 2– ·CO 2 formation in DMF as well as a new value for the diffusion coefficient of C 2 O 4 2– in DMF that differs substantially from previously reported values. Raman spectroscopy directly demonstrates C 2 O 4 2– ·CO 2 formation in DMF, while AIMD simulations predict that the solvent-dependent thermodynamics and mechanism for C 2 O 4 2– oxidation can be explained by C 2 O 4 2– –solvent and C 2 O 4 2– –CO 2 interactions. A byproduct of this investigation is the prediction from AIMD simulations that the C 2 O 4 2– ·CO 2 interaction in DMF destabilizes CO 2 . Consistent with this finding, cyclic voltammetry demonstrates that the thermodynamic potential for CO 2 reduction in DMF at a Hg electrode decreases by ∼0.3 V upon addition of C 2 O 4 2– to the solution.
Source: ACS electrochemistry.
Institutions: University of Utah, University of Minnesota
Language: English
Subfield: Electrochemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4414249815