Acidic ionic liquid/water solution as both medium and proton source for electrocatalytic H2 evolution by [Ni(P2N2)2]2+ complexes.
The electrocatalytic reduction of protons to H(2) by [Ni((P(Ph)(2)N(C6H4-hex))(2)(2)]((BF(4))(2) (where P(Ph)(2)N(C6H4-hex)(2) = 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(H(2)O)) 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)(2)N(C6H4X))(2)(2)]((BF(4))(2) (X = H, OMe,CH(2)P(O)(OEt)(2), Br) are also catalysts in the ionic liquid/water mixture, and the observed catalytic rates correlate with the hydrophobicity of X.
Center for Molecular Electrocatalysis, Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Douglas H
DH
Pool
Michael P
MP
Stewart
Molly
M
O'Hagan
Wendy J
WJ
Shaw
John A S
JA
Roberts
R Morris
RM
Bullock
Daniel L
DL
DuBois
D002384:Catalysis; D004563:Electrochemistry / Q000379:methods; D005296:Ferrous Compounds / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D011522:Protons; D014867:Water / Q000737:chemistry*
D005296:Ferrous Compounds; D011522:Protons; D014867:Water; D009532:Nickel