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Title: Minimal Proton Channel Enables H2 Oxidation and Production with a Water-Soluble Nickel-Based Catalyst

Hydrogenase enzymes efficiently interconvert H2 and H+ using first row transition metals with low overpotentials and high rates in aqueous solution. The development of efficient electrocatalysts mimicking the properties of hydrogenase enzymes for fuel and electrolysis cells based upon abundant and inexpensive metals could enable the widespread use of renewable fuels such as solar and wind. However, molecular electrocatalysts are typically unable to operate bidirectionally and are notably unable to meet the overall efficiency of the enzyme in either direction. Here we show that introducing an amino acid residue in the outer coordination sphere of a Ni-based complex Ni(PCy2NGlycine2)2 creates an electrocatalyst that is active and efficient for hydrogen oxidation (5-8 s-1, overpotential=44-250 mV) over a range of moderate pH values (3.5-9.0). Hydrogen production can be achieved from the same complex under identical solution conditions (>1200 s-1). Proton transfer from the amino acid carboxylates in the outer coordination sphere to the pendant amines in the second coordination sphere is observed by NMR and IR, signifying a plausible role of the carboxylate groups in creating a proton channel for proton removal and delivery during the catalytic cycle. These results with this first generation water soluble Ni(PR2NR’2)2 complex indicate that fast, bidirectionalmore » (hydrogen production/oxidation) catalysis for molecular catalysts is achievable. This work was funded by the Office of Science Early Career Research Program through the USDOE, BES (AD, SL, WJS), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US DOE, Office of Science, Office of BES (JH, JASR). Part of the research was conducted at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by U.S. DOE’s Office of Biological and Environmental Research (BER) program located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. Department of Energy.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
44681; KC0302010
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 135(49):18490-18496
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
catalysis; bioinspired; proton channel; outer coordination sphere; Environmental Molecular Sciences Laboratory