skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nickel phlorin intermediate formed by proton-coupled electron transfer in hydrogen evolution mechanism

Abstract

The development of more effective energy conversion processes is critical for global energy sustainability. The design of molecular electrocatalysts for the hydrogen evolution reaction is an important component of these efforts. Proton-coupled electron transfer (PCET) reactions, in which electron transfer is coupled to proton transfer, play an important role in these processes and can be enhanced by incorporating proton relays into the molecular electrocatalysts. In this work, nickel porphyrin electrocatalysts with and without an internal proton relay are investigated to elucidate the hydrogen evolution mechanisms and thereby enable the design of more effective catalysts. Density functional theory calculations indicate that electrochemical reduction leads to dearomatization of the porphyrin conjugated system, thereby favoring protonation at the meso carbon of the porphyrin ring to produce a phlorin intermediate. A key step in the proposed mechanisms is a thermodynamically favorable PCET reaction composed of intramolecular electron transfer from the nickel to the porphyrin and proton transfer from a carboxylic acid hanging group or an external acid to the meso carbon of the porphyrin. The C–H bond of the active phlorin acts similarly to the more traditional metal-hydride by reacting with acid to produce H 2. Support for the theoretically predicted mechanism is providedmore » by the agreement between simulated and experimental cyclic voltammograms in weak and strong acid and by the detection of a phlorin intermediate through spectroelectrochemical measurements. These results suggest that phlorin species have the potential to perform unique chemistry that could prove useful in designing more effective electrocatalysts.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Harvard Univ., Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Alexander von Humboldt Foundation; National Science Foundation (NSF)
OSTI Identifier:
1235503
Alternate Identifier(s):
OSTI ID: 1469107
Grant/Contract Number:  
SC0009758; CHE-1305124
Resource Type:
Journal Article: Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 113 Journal Issue: 3; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; electrocatalysis; metalloporphyrin; proton transfer; dearomatization

Citation Formats

Solis, Brian H., Maher, Andrew G., Dogutan, Dilek K., Nocera, Daniel G., and Hammes-Schiffer, Sharon. Nickel phlorin intermediate formed by proton-coupled electron transfer in hydrogen evolution mechanism. United States: N. p., 2015. Web. doi:10.1073/pnas.1521834112.
Solis, Brian H., Maher, Andrew G., Dogutan, Dilek K., Nocera, Daniel G., & Hammes-Schiffer, Sharon. Nickel phlorin intermediate formed by proton-coupled electron transfer in hydrogen evolution mechanism. United States. https://doi.org/10.1073/pnas.1521834112
Solis, Brian H., Maher, Andrew G., Dogutan, Dilek K., Nocera, Daniel G., and Hammes-Schiffer, Sharon. Thu . "Nickel phlorin intermediate formed by proton-coupled electron transfer in hydrogen evolution mechanism". United States. https://doi.org/10.1073/pnas.1521834112.
@article{osti_1235503,
title = {Nickel phlorin intermediate formed by proton-coupled electron transfer in hydrogen evolution mechanism},
author = {Solis, Brian H. and Maher, Andrew G. and Dogutan, Dilek K. and Nocera, Daniel G. and Hammes-Schiffer, Sharon},
abstractNote = {The development of more effective energy conversion processes is critical for global energy sustainability. The design of molecular electrocatalysts for the hydrogen evolution reaction is an important component of these efforts. Proton-coupled electron transfer (PCET) reactions, in which electron transfer is coupled to proton transfer, play an important role in these processes and can be enhanced by incorporating proton relays into the molecular electrocatalysts. In this work, nickel porphyrin electrocatalysts with and without an internal proton relay are investigated to elucidate the hydrogen evolution mechanisms and thereby enable the design of more effective catalysts. Density functional theory calculations indicate that electrochemical reduction leads to dearomatization of the porphyrin conjugated system, thereby favoring protonation at the meso carbon of the porphyrin ring to produce a phlorin intermediate. A key step in the proposed mechanisms is a thermodynamically favorable PCET reaction composed of intramolecular electron transfer from the nickel to the porphyrin and proton transfer from a carboxylic acid hanging group or an external acid to the meso carbon of the porphyrin. The C–H bond of the active phlorin acts similarly to the more traditional metal-hydride by reacting with acid to produce H2. Support for the theoretically predicted mechanism is provided by the agreement between simulated and experimental cyclic voltammograms in weak and strong acid and by the detection of a phlorin intermediate through spectroelectrochemical measurements. These results suggest that phlorin species have the potential to perform unique chemistry that could prove useful in designing more effective electrocatalysts.},
doi = {10.1073/pnas.1521834112},
url = {https://www.osti.gov/biblio/1235503}, journal = {Proceedings of the National Academy of Sciences of the United States of America},
issn = {0027-8424},
number = 3,
volume = 113,
place = {United States},
year = {2015},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at https://doi.org/10.1073/pnas.1521834112

Citation Metrics:
Cited by: 26 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Catalysis of the electrochemical reduction of carbon dioxide
journal, January 2013


Theoretical Analysis of Cobalt Hangman Porphyrins: Ligand Dearomatization and Mechanistic Implications for Hydrogen Evolution
journal, November 2014


Spin-orbit coupling in molecules: Chemistry beyond the adiabatic approximation
journal, July 2003


Density‐functional thermochemistry. III. The role of exact exchange
journal, April 1993


Proton-coupled electron transfer: classification scheme and guide to theoretical methods
journal, January 2012


Powering the planet: Chemical challenges in solar energy utilization
journal, October 2006


Electrochemical and spectroelectrochemical studies of nickel(II) porphyrins in dimethylformamide
journal, April 1988


Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production
journal, April 2012


Proton management as a design principle for hydrogenase-inspired catalysts
journal, January 2011


Determination of the C4H Bond Dissociation Energies of NADH Models and Their Radical Cations in Acetonitrile
journal, February 2003


Electrochemical Studies of Zinc Tetraphenylporphin
journal, January 1972


Proton-coupled electron transfer kinetics for the hydrogen evolution reaction of hangman porphyrins
journal, January 2012


NAD+ metabolism in health and disease
journal, January 2007


Molecular Electrocatalysts for the Oxidation of Hydrogen and the Production of Hydrogen - The Role of Pendant Amines as Proton Relays
journal, January 2011


Hydrogen Generation by Hangman Metalloporphyrins
journal, June 2011


Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins
journal, October 2014


The power to reduce: pyridine nucleotides – small molecules with a multitude of functions
journal, February 2007


Nature of hydrogen interactions with Ni(II) complexes containing cyclic phosphine ligands with pendant nitrogen bases
journal, March 2007


Moving Protons with Pendant Amines: Proton Mobility in a Nickel Catalyst for Oxidation of Hydrogen
journal, September 2011


Proton-Coupled Electron Transfer
journal, November 2007


Hydrogen Evolution Catalyzed by Cobalt Diimine–Dioxime Complexes
journal, May 2015


Proton-Coupled Electron Transfer: Moving Together and Charging Forward
journal, July 2015


Does one-electron transfer to nickel(II) porphyrins involve the metal or the porphyrin ligand?
journal, January 1989


H 2 Evolution and Molecular Electrocatalysts: Determination of Overpotentials and Effect of Homoconjugation
journal, November 2010


Digital simulations on unequally spaced grids.
journal, February 2003


Theory of Coupled Electron and Proton Transfer Reactions
journal, December 2010


Electrocatalytic Hydrogen Evolution at Low Overpotentials by Cobalt Macrocyclic Glyoxime and Tetraimine Complexes
journal, July 2007


Hydrogen Evolution Catalyzed by Cobaloximes
journal, December 2009


Chemistry of Personalized Solar Energy
journal, November 2009


Proton-Coupled Electron Transfer in Solution, Proteins, and Electrochemistry
journal, November 2008


Thermodynamics and kinetics of CO2, CO, and H+ binding to the metal centre of CO2reductioncatalysts
journal, January 2012


Terminal Hydride in [FeFe]-Hydrogenase Model Has Lower Potential for H 2 Production Than the Isomeric Bridging Hydride
journal, April 2008


PROTON-COUPLED ELECTRON TRANSFER: A Reaction Chemist's View
journal, June 2004


Proton-Coupled Electron Transfer Reactions:  Evaluation of Rate Constants
journal, January 1996


    Works referencing / citing this record:

    Homolytic versus Heterolytic Hydrogen Evolution Reaction Steered by a Steric Effect
    journal, March 2020


    Electrocatalytic H 2 Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand
    journal, June 2019


    Molecular Electrocatalysts for the Hydrogen Evolution Reaction: Input from Quantum Chemistry
    journal, October 2019


    Advances and challenges in understanding the electrocatalytic conversion of carbon dioxide to fuels
    journal, September 2019


    Electrochemical and spectroscopic methods for evaluating molecular electrocatalysts
    journal, May 2017


    A polypyridyl Co( ii ) complex-based water reduction catalyst with double H 2 evolution sites
    journal, January 2016


    A macrocyclic ‘Co 0 ’ complex: the relevance of ligand non-innocence to reactivity
    journal, January 2017


    Fluorescence quenching of the N -methylquinolinium cation by pairs of water or alcohol molecules
    journal, January 2018


    Hydrogen evolution by cobalt hangman porphyrins under operating conditions studied by vibrational spectro-electrochemistry
    journal, January 2018


    Remote ion-pair interactions in Fe-porphyrin-based molecular catalysts for the hydrogen evolution reaction
    journal, January 2019


    Recent progress in ligand-centered homogeneous electrocatalysts for hydrogen evolution reaction
    journal, January 2019


    Hydrogen gas generation using a metal-free fluorinated porphyrin
    journal, January 2018


    Electrocatalytic hydrogen evolution with gallium hydride and ligand-centered reduction
    journal, January 2019


    Rationally designed metal nanocluster for electrocatalytic hydrogen production from water
    journal, January 2018


    Importance of proton-coupled electron transfer in cathodic regeneration of organic hydrides
    journal, January 2019


    Storing redox equivalent in the phenalenyl backbone towards catalytic multi-electron reduction
    journal, January 2019


    Proton–hydride tautomerism in hydrogen evolution catalysis
    journal, May 2016


    Review on optofluidic microreactors for artificial photosynthesis
    journal, January 2018