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Title: Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

Abstract

Here, the hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.

Authors:
 [1];  [2];  [1];  [1];  [1];  [1];  [1];  [2];  [1]
  1. Harvard Univ., Cambridge, MA (United States)
  2. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
Publication Date:
Research Org.:
Harvard Univ., Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1348826
Grant/Contract Number:  
SC0009758
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 111; Journal Issue: 42; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; renewable; solar fuels; electrocatalysis

Citation Formats

Bediako, D. Kwabena, Solis, Brian H., Dogutan, Dilek K., Roubelakis, Manolis M., Maher, Andrew G., Lee, Chang Hoon, Chambers, Matthew B., Hammes-Schiffer, Sharon, and Nocera, Daniel G. Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins. United States: N. p., 2014. Web. doi:10.1073/pnas.1414908111.
Bediako, D. Kwabena, Solis, Brian H., Dogutan, Dilek K., Roubelakis, Manolis M., Maher, Andrew G., Lee, Chang Hoon, Chambers, Matthew B., Hammes-Schiffer, Sharon, & Nocera, Daniel G. Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins. United States. doi:10.1073/pnas.1414908111.
Bediako, D. Kwabena, Solis, Brian H., Dogutan, Dilek K., Roubelakis, Manolis M., Maher, Andrew G., Lee, Chang Hoon, Chambers, Matthew B., Hammes-Schiffer, Sharon, and Nocera, Daniel G. Wed . "Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins". United States. doi:10.1073/pnas.1414908111. https://www.osti.gov/servlets/purl/1348826.
@article{osti_1348826,
title = {Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins},
author = {Bediako, D. Kwabena and Solis, Brian H. and Dogutan, Dilek K. and Roubelakis, Manolis M. and Maher, Andrew G. and Lee, Chang Hoon and Chambers, Matthew B. and Hammes-Schiffer, Sharon and Nocera, Daniel G.},
abstractNote = {Here, the hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.},
doi = {10.1073/pnas.1414908111},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 42,
volume = 111,
place = {United States},
year = {Wed Oct 08 00:00:00 EDT 2014},
month = {Wed Oct 08 00:00:00 EDT 2014}
}

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Cited by: 35 works
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Works referenced in this record:

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