TY - JOUR
T1 - Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H2 evolution by [Ni(P2N2) 2]2+ complexes
AU - Pool, Douglas H.
AU - Stewart, Michael P.
AU - O'Hagan, Molly
AU - Shaw, Wendy J.
AU - Roberts, John A.S.
AU - Bullock, R. Morris
AU - DuBois, Daniel L.
PY - 2012/9/25
Y1 - 2012/9/25
N2 - 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.
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.
KW - Electrocatalysis
KW - Homogeneous
KW - Hydrogenase
KW - Proton relay
KW - Renewable energy
UR - http://www.scopus.com/inward/record.url?scp=84866874244&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84866874244&partnerID=8YFLogxK
U2 - 10.1073/pnas.1120208109
DO - 10.1073/pnas.1120208109
M3 - Article
C2 - 22685211
AN - SCOPUS:84866874244
VL - 109
SP - 15634
EP - 15639
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 39
ER -