A Modular, Energy-Based Approach to the Development of Nickel Containing Molecular Electrocatalysts for Hydrogen Production and Oxidation
This review discusses the development of molecular electrocatalysts for H2 production and oxidation based on nickel. A modular approach is used in which the structure of the catalyst is divided into first second and outer coordination spheres. The first coordination sphere consists of the ligands bound directly to the metal center, and this coordination sphere can be used to control such factors as the presence or absence of vacant coordination sites, redox potentials, hydride acceptor abilities and other important thermodynamic parameters. The second coordination sphere is defined as functional groups such as pendant acids or bases that can interact with bound substrates such as H2 molecules and hydride ligands, but that do not form strong bonds with the metal center. These functional groups can play diverse roles such as assisting the heterolytic cleavage of H2, controlling intra- and intermolecular proton transfer reactions, and provide a physical pathway for coupling proton and electron transfer reactions. By controlling both the hydride donor/acceptor ability of the catalysts using the first coordination sphere and the proton acceptor/donor abilities of the functional groups in the second coordination sphere, catalysts can be designed that are biased toward H2 production, H2 oxidation, or that are bidirectional (catalyzing both H2 oxidation and production). The outer coordination sphere is defined as that portion of the catalytic system that are not in the first and second coordination spheres. This coordination sphere can assist in the delivery of protons and electrons to and from the catalytically active site, thereby adding another important avenue for controlling catalytic activity. Many features of these simple catalytic systems are good models for enzymes and they provide the opportunity to probe certain aspects of catalysis that may be difficult in enzymes themselves, but that can provide insights into enzyme function and reactivity.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1132716
- Report Number(s):
- PNNL-SA-90765; KC0307010
- Journal Information:
- Biochimica et Biophysica Acta--Bioenergetics, 1827(8-9):1123-1139, Journal Name: Biochimica et Biophysica Acta--Bioenergetics, 1827(8-9):1123-1139
- Country of Publication:
- United States
- Language:
- English
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