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 language | English |
|---|---|
| Pages (from-to) | 9786-9793 |
| Number of pages | 8 |
| Journal | Dalton Transactions |
| Volume | 45 |
| Issue number | 24 |
| DOIs | |
| Publication status | Published - 2016 |
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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 journal › Article
}
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.
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U2 - 10.1039/c6dt00280c
DO - 10.1039/c6dt00280c
M3 - Article
VL - 45
SP - 9786
EP - 9793
JO - Dalton Transactions
JF - Dalton Transactions
SN - 1477-9226
IS - 24
ER -