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Title: Isotopic Probe Illuminates the Role of the Electrode Surface in Proton Coupled Hydride Transfer Electrochemical Reduction of Pyridinium on Pt(111)

A recently proposed mechanism for electrochemical CO 2 reduction on Pt (111) catalyzed by aqueous acidic pyridine solutions suggests that the observed redox potential of ca. -600 mV vs. SCE is due to the one-electron reduction of pyridinium through proton coupled electron transfer (PCET) to form H atoms adsorbed on the Pt surface (H ads). The initial pyridinium reduction was probed isotopically via deuterium substitution. A combined experimental and theoretical analysis found equilibrium isotope effects (EIE) due to deuterium substitution at the acidic pyridinium site. A shift in the cathodic cyclic voltammetric half wave potential of -25 mV was observed, consistent with the theoretical prediction of -40 mV based on the recently proposed reaction mechanism where pyridinium is essential to establish a high concentration of Bronsted acid in contact with the substrate CO 2 and with the Pt surface. A prefeature in the cyclic voltammogram was examined under isotopic substitution and indicated an H-ads intermediate in pyridinium reduction. In conclusion, the theoretical prediction and observation of an BM supported the assignment of the cathodic wave to the proposed reduction of pyridinium through PCET forming H ads and eventually H 2 on the Pt surface.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [1]
  1. Princeton Univ., Princeton, NJ (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States); Yale Univ., New Haven, CT (United States)
  3. Yale Univ., New Haven, CT (United States)
Publication Date:
Grant/Contract Number:
SC0002133
Type:
Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 162; Journal Issue: 14; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Contributing Orgs:
Princeton University Yale University
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 14 SOLAR ENERGY; 25 ENERGY STORAGE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; carbon-dioxide; co2 reduction; supporting electrolyte; hydrogen adsorption; weak acid; density functional theory; electrocatalysis; isotope effect; proton coupled electron transfer; Pyridinium
OSTI Identifier:
1418441