scholarly journals Proton reduction by molecular catalysts in water under demanding atmospheres

2014 ◽  
Vol 50 (100) ◽  
pp. 15995-15998 ◽  
Author(s):  
David W. Wakerley ◽  
Manuela A. Gross ◽  
Erwin Reisner
Keyword(s):  
Proton Reduction ◽  
Reduction Activity ◽  
Molecular Catalysts

The electrocatalytic proton reduction activity of a Ni bis(diphosphine) and a cobaloxime catalyst has been studied in water in the presence of the gaseous inhibitors O2 and CO.

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

2020 ◽  
Author(s):  
Peter T. Smith ◽  
Sophia Weng ◽  
Christopher Chang
Keyword(s):  
Proton Transfer ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Redox Mediators ◽  
Reservoir Properties ◽  
Proton Reduction ◽  
Electrochemical Co2 Reduction ◽  
Starting Point ◽  
Rate Improvement ◽  
Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

Molecular Catalysts Immobilized on Semiconductor Photosensitizers for Proton Reduction toward Visible‐Light‐Driven Overall Water Splitting

ChemSusChem ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1807-1824 ◽  
Author(s):  
Takeshi Morikawa ◽  
Shunsuke Sato ◽  
Keita Sekizawa ◽  
Takeo Arai ◽  
Tomiko M. Suzuki
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Proton Reduction ◽  
Overall Water Splitting ◽  
Visible Light Driven ◽  
Molecular Catalysts

Effect of Lewis Basic Amine Site on Proton Reduction Activity of NNN‐Co Pincer Complex

2021 ◽  
Author(s):  
Seungjin Song ◽  
Jaewhan Cho ◽  
Hyeonjeong Jo ◽  
Junseong Lee ◽  
Jun‐Ho Choi ◽  
...  
Keyword(s):  
Proton Reduction ◽  
Reduction Activity ◽  
Pincer Complex ◽  
Basic Amine

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

2020 ◽  
Author(s):  
Peter T. Smith ◽  
Sophia Weng ◽  
Christopher Chang
Keyword(s):  
Proton Transfer ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Redox Mediators ◽  
Reservoir Properties ◽  
Proton Reduction ◽  
Electrochemical Co2 Reduction ◽  
Starting Point ◽  
Rate Improvement ◽  
Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

scholarly journals A Beginner’s Guide to Thermodynamic Modelling of [FeFe] Hydrogenase

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 238
Author(s):  
James A. Birrell ◽  
Patricia Rodríguez-Maciá ◽  
Adrian Hery-Barranco
Keyword(s):  
Infrared Spectroscopy ◽  
Thermodynamic Parameters ◽  
Active Site ◽  
Hydrogen Oxidation ◽  
Thermodynamic Models ◽  
Nernst Equation ◽  
Proton Reduction ◽  
Redox Behaviour ◽  
Naturally Occurring ◽  
Molecular Catalysts

[FeFe] hydrogenases, which are considered the most active naturally occurring catalysts for hydrogen oxidation and proton reduction, are extensively studied as models to learn the important features for efficient H2 conversion catalysis. Using infrared spectroscopy as a selective probe, the redox behaviour of the active site H-cluster is routinely modelled with thermodynamic schemes based on the Nernst equation for determining thermodynamic parameters, such as redox midpoint potentials and pKa values. Here, the thermodynamic models usually applied to [FeFe] hydrogenases are introduced and discussed in a pedagogic fashion and their applicability to additional metalloenzymes and molecular catalysts is also addressed.

scholarly journals High Turnover Frequency H2 Evolution Electrocatalysis at Low Acid Concentration Promoted by Bioinspired (NCS2)Ni(II) Complexes

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Nigam P. Rath ◽  
Liviu M. Mirica
Keyword(s):  
Renewable Energy Sources ◽  
Electrochemical Analysis ◽  
Redox Couple ◽  
Turnover Frequency ◽  
High Turnover ◽  
Proton Reduction ◽  
Paramagnetic Resonance ◽  
High Proton ◽  
Molecular Catalysts ◽  
Strong Acids

Electrochemical proton reduction to produce hydrogen is considered a sustainable approach to shift the fossil fuel-based energy production toward renewable energy sources. Although the development of molecular electrocatalysts for the hydrogen evolution reaction (HER) has gained significant attention, most of these molecular catalysts require either strong acids or often operate at high proton concentration to achieve high turnover. Herein, we report the synthesis and charcterization of two Ni<sup>II</sup> complexes, [(N2S2)Ni(MeCN)<sub>2</sub>](OTf)<sub>2</sub> (<b>1</b><b>•(OTf)<sub>2</sub></b>) and (NCHS2)Ni(OTf)<sub>2</sub> (<b>2</b>) bearing bioinspired 3,7-dithia-1,5(2,6)-dipyridinacyclooctaphane (N2S2) and 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane (NCHS2) ligands, respectively, along with their electrochemical HER in a non-aqueous electrolyte. Our Ni complexes show high turnover frequencies greater than 200,000 s<sup>–1</sup> in the presence of 0.043 M of trifluoroacetic acid with ≥1 M of water present. Under these electrochemical conditions, <b>2</b> exhibited 2.5-fold faster kinetics at 240 mV lower overpotential than that of <b>1</b><sup>2+</sup>. Furthermore, <b>2</b> initiates electrochemical proton reduction at the potential where Ni<sup>II/I</sup> redox couple occurs, whereas the similar HER electrocatalysis carried out by <b>1</b><sup>2+</sup><sub> </sub>was observed at the potential for the Ni<sup>I/0</sup> redox couple. The electrochemical analysis revealed that <b>2</b> undergoes an uncommon HER mechanism proposed to involve a Ni<sup>III</sup>–hydride species – a typical pathway followed by [NiFe] hydrogenase enzymes, upon activating the C–H bond of the coordinating NCHS2 ligand, and the resulting organometallic Ni complex is proposed to be the active HER electrocatalyst. This organometallic Ni complex derivative, [(NCS2)Ni(MeCN)<sub>2</sub>]<sup>2+</sup> (<b>5</b>) was synthesized independently and its performance for the HER supports the proposed HER mechanism for <b>2</b>. Additionally, electron paramagnetic resonance (EPR) spectroscopy was employed to probe the accessibility to Ni<sup>I</sup> and Ni<sup>III</sup> species proposed as intermediates in the described HER mechanisms. Importantly, comparative catalytic Tafel plots were constructed to benchmark the HER activity of <b>1</b><sup>2+</sup> and <b>2</b> versus previously reported known Ni-based HER electrocatalysts. Overall, the organometallic (NCS2)Ni system reported below represents a novel bioinspired molecular HER electrocatalyst that exhibits a high turnover frequency and more closely resembles the Ni<sup>I</sup>/Ni<sup>III</sup> HER mechanism proposed to pe operative in [NiFe] hydrogenases.

Electrocatalytic reduction of protons to hydrogen by a copper complex of the pentadentate ligand Dmphen-DPA in a nonaqueous electrolyte

2019 ◽  
Vol 43 (46) ◽  
pp. 18134-18140
Author(s):  
Ying-Chun Gao ◽  
Ying-Guo Zhao ◽  
Xiao-Wei Song ◽  
Rong-Yi Huang ◽  
Yan Meng ◽  
...  
Keyword(s):  
Copper Complex ◽  
Electrocatalytic Reduction ◽  
Proton Reduction ◽  
Reduction Activity ◽  
Nonaqueous Electrolyte ◽  
Plausible Mechanism ◽  
Pentadentate Ligand

An aminopyridine-based copper complex was synthesized and investigated for its electrocatalytic proton reduction activity and the plausible mechanism.

Molecular Catalysts for Proton Reduction Based on Non-noble Metals

2018 ◽  
pp. 489-527
Author(s):  
Catherine Elleouet ◽  
François Y. Pétillon ◽  
Philippe Schollhammer
Keyword(s):  
Noble Metals ◽  
Proton Reduction ◽  
Molecular Catalysts

scholarly journals High Turnover Frequency H2 Evolution Electrocatalysis at Low Acid Concentration Promoted by Bioinspired (NCS2)Ni(II) Complexes

2021 ◽  
Author(s):  
Soumalya Sinha ◽  
Giang N. Tran ◽  
Hanah Na ◽  
Nigam P. Rath ◽  
Liviu M. Mirica
Keyword(s):  
Renewable Energy Sources ◽  
Electrochemical Analysis ◽  
Redox Couple ◽  
Turnover Frequency ◽  
High Turnover ◽  
Proton Reduction ◽  
Paramagnetic Resonance ◽  
High Proton ◽  
Molecular Catalysts ◽  
Strong Acids

Electrochemical proton reduction to produce hydrogen is considered a sustainable approach to shift the fossil fuel-based energy production toward renewable energy sources. Although the development of molecular electrocatalysts for the hydrogen evolution reaction (HER) has gained significant attention, most of these molecular catalysts require either strong acids or often operate at high proton concentration to achieve high turnover. Herein, we report the synthesis and charcterization of two Ni<sup>II</sup> complexes, [(N2S2)Ni(MeCN)<sub>2</sub>](OTf)<sub>2</sub> (<b>1</b><b>•(OTf)<sub>2</sub></b>) and (NCHS2)Ni(OTf)<sub>2</sub> (<b>2</b>) bearing bioinspired 3,7-dithia-1,5(2,6)-dipyridinacyclooctaphane (N2S2) and 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane (NCHS2) ligands, respectively, along with their electrochemical HER in a non-aqueous electrolyte. Our Ni complexes show high turnover frequencies greater than 200,000 s<sup>–1</sup> in the presence of 0.043 M of trifluoroacetic acid with ≥1 M of water present. Under these electrochemical conditions, <b>2</b> exhibited 2.5-fold faster kinetics at 240 mV lower overpotential than that of <b>1</b><sup>2+</sup>. Furthermore, <b>2</b> initiates electrochemical proton reduction at the potential where Ni<sup>II/I</sup> redox couple occurs, whereas the similar HER electrocatalysis carried out by <b>1</b><sup>2+</sup><sub> </sub>was observed at the potential for the Ni<sup>I/0</sup> redox couple. The electrochemical analysis revealed that <b>2</b> undergoes an uncommon HER mechanism proposed to involve a Ni<sup>III</sup>–hydride species – a typical pathway followed by [NiFe] hydrogenase enzymes, upon activating the C–H bond of the coordinating NCHS2 ligand, and the resulting organometallic Ni complex is proposed to be the active HER electrocatalyst. This organometallic Ni complex derivative, [(NCS2)Ni(MeCN)<sub>2</sub>]<sup>2+</sup> (<b>5</b>) was synthesized independently and its performance for the HER supports the proposed HER mechanism for <b>2</b>. Additionally, electron paramagnetic resonance (EPR) spectroscopy was employed to probe the accessibility to Ni<sup>I</sup> and Ni<sup>III</sup> species proposed as intermediates in the described HER mechanisms. Importantly, comparative catalytic Tafel plots were constructed to benchmark the HER activity of <b>1</b><sup>2+</sup> and <b>2</b> versus previously reported known Ni-based HER electrocatalysts. Overall, the organometallic (NCS2)Ni system reported below represents a novel bioinspired molecular HER electrocatalyst that exhibits a high turnover frequency and more closely resembles the Ni<sup>I</sup>/Ni<sup>III</sup> HER mechanism proposed to pe operative in [NiFe] hydrogenases.

scholarly journals Enhancing H2 evolution performance of an immobilised cobalt catalyst by rational ligand design

2015 ◽  
Vol 6 (5) ◽  
pp. 2727-2736 ◽  
Author(s):  
Janina Willkomm ◽  
Nicoleta M. Muresan ◽  
Erwin Reisner
Keyword(s):  
Cobalt Catalyst ◽  
Ligand Design ◽  
H2 Evolution ◽  
Proton Reduction ◽  
Reduction Activity ◽  
Rational Ligand Design

Rational ligand design was employed to improve the proton reduction activity of an immobilised cobalt diimine–dioxime catalyst.

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