Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H2 evolution by [Ni(P2N2) 2]2+ complexes

Douglas H. Pool; Michael P. Stewart; Molly O'Hagan; Wendy J. Shaw; John A.S. Roberts; R. Morris Bullock; Daniel L. DuBois

doi:10.1073/pnas.1120208109

Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H₂ evolution by [Ni(P₂N₂) ₂]²⁺ complexes

Douglas H. Pool, Michael P. Stewart, Molly O'Hagan, Wendy J. Shaw, John A.S. Roberts, R. Morris Bullock, Daniel L. DuBois

Pacific Northwest National Laboratory

Research output: Contribution to journal › Article › peer-review

64 Citations (Scopus)

Abstract

The electrocatalytic reduction of protons to H₂ by [Ni(P ^Ph₂N^C6H4-hex₂)₂](BF ₄)₂ (where P^Ph₂N ^C6H4-hex₂ = 1,5-di(4-n-hexylphenyl)-3,7-diphenyl-1,5- diaza-3,7-diphosphacyclooctane) in the highly acidic ionic liquid dibutylformamidium bis(trifluoromethanesulfonyl)amide shows a strong dependence on added water. A turnover frequency of 43,000-53,000 s^-1 has been measured for hydrogen production at 25°C when the mole fraction of water (χ_H2O) is 0.72. The same catalyst in acetonitrile with added dimethylformamidium trifluoromethanesulfonate and water has a turnover frequency of 720 s^-1. Thus, the use of an ionic liquid/aqueous solution enhances the observed catalytic rate by more than a factor of 50, compared to a similar acid in a traditional organic solvent. Complexes [Ni(P^Ph ₂N^C6H4X₂)₂](BF₄) ₂ (X = H, OMe,CH₂P(O)(OEt)₂, Br) are also catalysts in the ionic liquid/water mixture, and the observed catalytic rates correlate with the hydrophobicity of X.

Original language	English
Pages (from-to)	15634-15639
Number of pages	6
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	109
Issue number	39
DOIs	https://doi.org/10.1073/pnas.1120208109
Publication status	Published - Sep 25 2012

Keywords

Electrocatalysis
Homogeneous
Hydrogenase
Proton relay
Renewable energy

ASJC Scopus subject areas

General

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10.1073/pnas.1120208109

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Pool, D. H., Stewart, M. P., O'Hagan, M., Shaw, W. J., Roberts, J. A. S., Bullock, R. M., & DuBois, D. L. (2012). Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H₂ evolution by [Ni(P₂N₂) ₂]²⁺ complexes. Proceedings of the National Academy of Sciences of the United States of America, 109(39), 15634-15639. https://doi.org/10.1073/pnas.1120208109

Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H₂ evolution by [Ni(P₂N₂) ₂]²⁺ complexes. / Pool, Douglas H.; Stewart, Michael P.; O'Hagan, Molly; Shaw, Wendy J.; Roberts, John A.S.; Bullock, R. Morris ; DuBois, Daniel L.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 39, 25.09.2012, p. 15634-15639.

Research output: Contribution to journal › Article › peer-review

Pool, DH, Stewart, MP, O'Hagan, M, Shaw, WJ, Roberts, JAS , Bullock, RM & DuBois, DL 2012, 'Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H₂ evolution by [Ni(P₂N₂) ₂]²⁺ complexes', Proceedings of the National Academy of Sciences of the United States of America, vol. 109, no. 39, pp. 15634-15639. https://doi.org/10.1073/pnas.1120208109

Pool, Douglas H. ; Stewart, Michael P. ; O'Hagan, Molly ; Shaw, Wendy J. ; Roberts, John A.S. ; Bullock, R. Morris ; DuBois, Daniel L. / Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H₂ evolution by [Ni(P₂N₂) ₂]²⁺ complexes. In: Proceedings of the National Academy of Sciences of the United States of America. 2012 ; Vol. 109, No. 39. pp. 15634-15639.

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abstract = "The electrocatalytic reduction of protons to H2 by [Ni(P Ph2NC6H4-hex2)2](BF 4)2 (where PPh2N C6H4-hex2 = 1,5-di(4-n-hexylphenyl)-3,7-diphenyl-1,5- diaza-3,7-diphosphacyclooctane) in the highly acidic ionic liquid dibutylformamidium bis(trifluoromethanesulfonyl)amide shows a strong dependence on added water. A turnover frequency of 43,000-53,000 s-1 has been measured for hydrogen production at 25°C when the mole fraction of water (χH2O) is 0.72. The same catalyst in acetonitrile with added dimethylformamidium trifluoromethanesulfonate and water has a turnover frequency of 720 s-1. Thus, the use of an ionic liquid/aqueous solution enhances the observed catalytic rate by more than a factor of 50, compared to a similar acid in a traditional organic solvent. Complexes [Ni(PPh 2NC6H4X2)2](BF4) 2 (X = H, OMe,CH2P(O)(OEt)2, Br) are also catalysts in the ionic liquid/water mixture, and the observed catalytic rates correlate with the hydrophobicity of X.",

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AB - The electrocatalytic reduction of protons to H2 by [Ni(P Ph2NC6H4-hex2)2](BF 4)2 (where PPh2N C6H4-hex2 = 1,5-di(4-n-hexylphenyl)-3,7-diphenyl-1,5- diaza-3,7-diphosphacyclooctane) in the highly acidic ionic liquid dibutylformamidium bis(trifluoromethanesulfonyl)amide shows a strong dependence on added water. A turnover frequency of 43,000-53,000 s-1 has been measured for hydrogen production at 25°C when the mole fraction of water (χH2O) is 0.72. The same catalyst in acetonitrile with added dimethylformamidium trifluoromethanesulfonate and water has a turnover frequency of 720 s-1. Thus, the use of an ionic liquid/aqueous solution enhances the observed catalytic rate by more than a factor of 50, compared to a similar acid in a traditional organic solvent. Complexes [Ni(PPh 2NC6H4X2)2](BF4) 2 (X = H, OMe,CH2P(O)(OEt)2, Br) are also catalysts in the ionic liquid/water mixture, and the observed catalytic rates correlate with the hydrophobicity of X.

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