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Title: Graphite-Conjugated Acids Reveal a Molecular Framework for Proton-Coupled Electron Transfer at Electrode Surfaces

Journal Article · · ACS Central Science

Proton-coupled electron-transfer (PCET) steps play a key role in energy conversion reactions. Molecular PCET reactions are well-described by “square schemes” in which the overall thermochemistry of the reaction is broken into its constituent proton-transfer and electron-transfer components. Although this description has been essential for understanding molecular PCET, no such framework exists for PCET reactions that take place at electrode surfaces. Herein, we develop a molecular square scheme framework for interfacial PCET by investigating the electrochemistry of molecularly well-defined acid/base sites conjugated to graphitic electrodes. Using cyclic voltammetry, we first demonstrate that, irrespective of the redox properties of the corresponding molecular analogue, proton transfer to graphite-conjugated acid/base sites is coupled to electron transfer. We then show that the thermochemistry of surface PCET events can be described by the pKa of the molecular analogue and the potential of zero free charge (zero-field reduction potential) of the electrode. Finally, this work provides a general framework for analyzing and predicting the thermochemistry of interfacial PCET reactions.

Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC0014176
OSTI ID:
1510160
Alternate ID(s):
OSTI ID: 1515187
Journal Information:
ACS Central Science, Vol. 5, Issue 5; ISSN 2374-7943
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Coupling Theory to Electrode Design for Electrocatalysis journal May 2019
Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis journal July 2019

Figures / Tables (8)