Optimizing conditions for utilization of an H2 oxidation catalyst with outer coordination sphere functionalities

Arnab Dutta, Bojana Ginovska, Simone Raugei, John Roberts, Wendy J. Shaw

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

As a starting point for evaluating a broader range of conditions for H2 oxidation complexes, in this work we investigate an efficient and reversible Ni-based H2 oxidation and production complex with an arginine in the outer coordination sphere, [Ni(PCy 2NArginine 2)2]7+ (CyArg). We tested this complex under a wide range of pressures and temperatures, in two different solvents (methanol and water), to determine if simultaneous improvements in rate and overpotential could be achieved. We found that the optimal conditions combined both high temperature (72 °C) and pressure (100 atm H2) in acidic aqueous solution (pH = 1), resulting in the fastest H2 oxidation reported for any homogeneous electrocatalyst to date (TOF 1.1 × 106 s-1) operating at 240 mV overpotential. The activation free energy in water was determined to be 10 kcal mol-1 at all pressures studied. Surprisingly, in methanol under the same temperature and pressure, CyArg had a TOF for H2 oxidation of only 280 s-1 at an overpotential of 750 mV. Comparisons to the data in water, and to a control complex, [Ni(PCy 2NBenzyl 2)2]2+ (CyBn; Bn = benzyl), suggest that this substantial difference is likely due to a change in rate limiting step from H2 addition to deprotonation. Importantly, the optimal conditions we identified for CyArg (elevated temperature and acidic aqueous solutions), are amenable to fuel cell technologies and provide an important advancement in implementing homogeneous synthetic catalysts for renewable energy.

Original languageEnglish
Pages (from-to)9786-9793
Number of pages8
JournalDalton Transactions
Volume45
Issue number24
DOIs
Publication statusPublished - 2016

Fingerprint

Oxidation
Catalysts
Methanol
Water
Temperature
Deprotonation
Electrocatalysts
Free energy
Arginine
Fuel cells
Chemical activation

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Optimizing conditions for utilization of an H2 oxidation catalyst with outer coordination sphere functionalities. / Dutta, Arnab; Ginovska, Bojana; Raugei, Simone; Roberts, John; Shaw, Wendy J.

In: Dalton Transactions, Vol. 45, No. 24, 2016, p. 9786-9793.

Research output: Contribution to journalArticle

@article{26ff66cfc50f401d8b7a2291773884c5,
title = "Optimizing conditions for utilization of an H2 oxidation catalyst with outer coordination sphere functionalities",
abstract = "As a starting point for evaluating a broader range of conditions for H2 oxidation complexes, in this work we investigate an efficient and reversible Ni-based H2 oxidation and production complex with an arginine in the outer coordination sphere, [Ni(PCy 2NArginine 2)2]7+ (CyArg). We tested this complex under a wide range of pressures and temperatures, in two different solvents (methanol and water), to determine if simultaneous improvements in rate and overpotential could be achieved. We found that the optimal conditions combined both high temperature (72 °C) and pressure (100 atm H2) in acidic aqueous solution (pH = 1), resulting in the fastest H2 oxidation reported for any homogeneous electrocatalyst to date (TOF 1.1 × 106 s-1) operating at 240 mV overpotential. The activation free energy in water was determined to be 10 kcal mol-1 at all pressures studied. Surprisingly, in methanol under the same temperature and pressure, CyArg had a TOF for H2 oxidation of only 280 s-1 at an overpotential of 750 mV. Comparisons to the data in water, and to a control complex, [Ni(PCy 2NBenzyl 2)2]2+ (CyBn; Bn = benzyl), suggest that this substantial difference is likely due to a change in rate limiting step from H2 addition to deprotonation. Importantly, the optimal conditions we identified for CyArg (elevated temperature and acidic aqueous solutions), are amenable to fuel cell technologies and provide an important advancement in implementing homogeneous synthetic catalysts for renewable energy.",
author = "Arnab Dutta and Bojana Ginovska and Simone Raugei and John Roberts and Shaw, {Wendy J.}",
year = "2016",
doi = "10.1039/c6dt00280c",
language = "English",
volume = "45",
pages = "9786--9793",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "24",

}

TY - JOUR

T1 - Optimizing conditions for utilization of an H2 oxidation catalyst with outer coordination sphere functionalities

AU - Dutta, Arnab

AU - Ginovska, Bojana

AU - Raugei, Simone

AU - Roberts, John

AU - Shaw, Wendy J.

PY - 2016

Y1 - 2016

N2 - As a starting point for evaluating a broader range of conditions for H2 oxidation complexes, in this work we investigate an efficient and reversible Ni-based H2 oxidation and production complex with an arginine in the outer coordination sphere, [Ni(PCy 2NArginine 2)2]7+ (CyArg). We tested this complex under a wide range of pressures and temperatures, in two different solvents (methanol and water), to determine if simultaneous improvements in rate and overpotential could be achieved. We found that the optimal conditions combined both high temperature (72 °C) and pressure (100 atm H2) in acidic aqueous solution (pH = 1), resulting in the fastest H2 oxidation reported for any homogeneous electrocatalyst to date (TOF 1.1 × 106 s-1) operating at 240 mV overpotential. The activation free energy in water was determined to be 10 kcal mol-1 at all pressures studied. Surprisingly, in methanol under the same temperature and pressure, CyArg had a TOF for H2 oxidation of only 280 s-1 at an overpotential of 750 mV. Comparisons to the data in water, and to a control complex, [Ni(PCy 2NBenzyl 2)2]2+ (CyBn; Bn = benzyl), suggest that this substantial difference is likely due to a change in rate limiting step from H2 addition to deprotonation. Importantly, the optimal conditions we identified for CyArg (elevated temperature and acidic aqueous solutions), are amenable to fuel cell technologies and provide an important advancement in implementing homogeneous synthetic catalysts for renewable energy.

AB - As a starting point for evaluating a broader range of conditions for H2 oxidation complexes, in this work we investigate an efficient and reversible Ni-based H2 oxidation and production complex with an arginine in the outer coordination sphere, [Ni(PCy 2NArginine 2)2]7+ (CyArg). We tested this complex under a wide range of pressures and temperatures, in two different solvents (methanol and water), to determine if simultaneous improvements in rate and overpotential could be achieved. We found that the optimal conditions combined both high temperature (72 °C) and pressure (100 atm H2) in acidic aqueous solution (pH = 1), resulting in the fastest H2 oxidation reported for any homogeneous electrocatalyst to date (TOF 1.1 × 106 s-1) operating at 240 mV overpotential. The activation free energy in water was determined to be 10 kcal mol-1 at all pressures studied. Surprisingly, in methanol under the same temperature and pressure, CyArg had a TOF for H2 oxidation of only 280 s-1 at an overpotential of 750 mV. Comparisons to the data in water, and to a control complex, [Ni(PCy 2NBenzyl 2)2]2+ (CyBn; Bn = benzyl), suggest that this substantial difference is likely due to a change in rate limiting step from H2 addition to deprotonation. Importantly, the optimal conditions we identified for CyArg (elevated temperature and acidic aqueous solutions), are amenable to fuel cell technologies and provide an important advancement in implementing homogeneous synthetic catalysts for renewable energy.

UR - http://www.scopus.com/inward/record.url?scp=84975090522&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84975090522&partnerID=8YFLogxK

U2 - 10.1039/c6dt00280c

DO - 10.1039/c6dt00280c

M3 - Article

AN - SCOPUS:84975090522

VL - 45

SP - 9786

EP - 9793

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 24

ER -