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Title: Standard reduction potentials for oxygen and carbon dioxide couples in acetonitrile and N,N -dimethylformamide

A variety of next-generation energy processes utilize the electrochemical interconversions of dioxygen and water as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Reported here are the first estimates of the standard reduction potential of the O2 + 4e + 4H+ ⇌ 2H2O couple in organic solvents. The values are +1.21 V in acetonitrile (MeCN) and +0.60 V in N,N-dimethylformamide (DMF), each versus the ferrocenium/ferrocene couple (Fc+/0) in the respective solvent (as are all of the potentials reported here). The potentials have been determined using a thermochemical cycle that combines the free energy for transferring water from aqueous solution to organic solvent, –0.43 kcal mol–1 for MeCN and –1.47 kcal mol–1 for DMF, and the potential of the H+/H2 couple, – 0.028 V in MeCN and –0.662 V in DMF. The H+/H2 couple in DMF has been directly measured electrochemically using the previously reported procedure for the MeCN value. The thermochemical approach used for the O2/H2O couple has been extended to the CO2/CO and CO2/CH4 couples to give values of –0.12 and +0.15 V in MeCN and –0.73 and –0.48 V in DMF, respectively. Here, extensions to other reduction potentials are discussed. Additionally, the free energy formore » transfer of protons from water to organic solvent is estimated as +14 kcal mol–1 for acetonitrile and +0.6 kcal mol–1 for DMF.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1]
  1. Yale Univ., New Haven, CT (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); (J.A.S.R.) REC Silicon, Moses Lake, WA (United States)
  3. Univ. of Washington, Seattle, WA (United States); FireWater Fuel Corp., Calgary, AB (Canada)
  4. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Report Number(s):
PNNL-SA-111283
Journal ID: ISSN 0020-1669; KC0307010
Grant/Contract Number:
AC05-76RL01830
Type:
Published Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 54; Journal Issue: 24; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; oxygen reduction; thermodynamic potentials
OSTI Identifier:
1228284
Alternate Identifier(s):
OSTI ID: 1255410