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Arginine‐Containing Ligands Enhance H 2 Oxidation Catalyst Performance
Author(s) -
Dutta Arnab,
Roberts John A. S.,
Shaw Wendy J.
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201402304
Subject(s) - overpotential , electrocatalyst , chemistry , catalysis , hydrogenase , arginine , medicinal chemistry , coordination sphere , intramolecular force , inorganic chemistry , crystallography , stereochemistry , electrochemistry , organic chemistry , amino acid , biochemistry , crystal structure , electrode
Abstract Hydrogenase enzymes use Ni and Fe to oxidize H 2 at high turnover frequencies (TOF) (up to 10 000 s −1 ) and low overpotentials (<100 mV). In comparison, the fastest reported synthetic electrocatalyst, [Ni II (P Cy 2 N t Bu 2 ) 2 ] 2+ , oxidizes H 2 at 60 s −1 in MeCN under 1 atm H 2 with an unoptimized overpotential of ca. 500 mV using triethylamine as a base.1 Here we show that a structured outer coordination sphere in a Ni electrocatalyst enhances H 2 oxidation activity: [Ni II (P Cy 2 N Arg 2 ) 2 ] 8+ (Arg=arginine) has a TOF of 210 s −1 in water with high energy efficiency (180 mV overpotential) under 1 atm H 2 , and 144 000 s −1 (460 mV overpotential) under 133 atm H 2 . The complex is active from pH 0–14 and is faster at low pH, the most relevant condition for fuel cells. The arginine substituents increase TOF and may engage in an intramolecular guanidinium interaction that assists in H 2 activation, while the COOH groups facilitate rapid proton movement. These results emphasize the critical role of features beyond the active site in achieving fast, efficient catalysis.