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Novel Multinuclear Catalysts for the Electroreduction of Dioxygen Directly to Water

Anson, Fred C. and Shi, Chunnian and Steiger, Beat (1997) Novel Multinuclear Catalysts for the Electroreduction of Dioxygen Directly to Water. Accounts of Chemical Research, 30 (11). pp. 437-444. ISSN 0001-4842. doi:10.1021/ar960264j.

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The electroreduction of O_2 to H_2O in aqueous acid at potentials close to the thermodynamically permitted value remains a daunting challenge for designers of superior fuel cells and batteries that utilize dioxygen as the reducible reactant. The four-electron reduction of O_2, which involves the rupture of the O-O bond and the formation of four O-H bonds, requires the use of catalysts to obtain useful rates at cathode potentials of interest in practical applications. The standard potential of the O_2/H_2O couple in solutions containing 1 M H^+ and saturated with O_2 at 1 atm is ca. 1.0 V (vs the saturated calomel electrode, SCE), but the highest cathode potentials achievable with currently available catalysts are closer to 0.55 V. (Molecules, functional groups, or metallic deposits that accelerate the rates of electrode reactions when they are confined to the surfaces of electrodes are often called electrocatalysts, a terminology that will be adopted in this Account.) Finely divided platinum supported on high area carbon is the electrocatalyst employed most frequently to achieve the electroreduction of O_2 to H_2O in presently available fuel cells. However, this type of electrocatalyst suffers from the disadvantages of high cost and gradual loss in catalytic activity as the surface area of the active platinum particles decreases because of sintering, dissolution, physical dislodgment, and/or adsorption of impurities. Searches for superior electrocatalysts for the reduction of O2 have often focused on cobalt porphyrins which are well-known to exhibit electrocatalytic activity toward the reduction of O_2, although H_2O_2 instead of H_2O is the usual product. However, it was discovered in recent years that a variety of molecular catalysts consisting of dimeric cofacial cobalt porphyrins adsorbed on the surface of graphite electrodes are able to catalyze the direct four-electron electroreduction of O_2 without passing through H_2O_2 as an intermediate. Both dimeric and monomeric iridium por phyrins have also been found to accomplish the electroreduction of O_2 to H_2O at unusually positive potentials. The mechanisms through which dimeric electrocatalysts are believed to operate involve the simultaneous interaction of both metal centers with the two oxygen atoms of the O_2 molecule as the O-O bond is severed. The ideas and strategies that underlay the development of these electrocatalysts have been described.

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Additional Information:© 1997 American Chemical Society. Received April 2, 1997. Publication Date (Web): November 13, 1997. The research described in this Account was supported by the National Science Foundation and by ONR/DARPA.
Funding AgencyGrant Number
Office of Naval Research (ONR)UNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20171122-083839178
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Official Citation:Novel Multinuclear Catalysts for the Electroreduction of Dioxygen Directly to Water. Fred C. Anson, Chunnian Shi, and Beat Steiger. Accounts of Chemical Research 1997 30 (11), 437-444 DOI: 10.1021/ar960264j
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83425
Deposited By: Tony Diaz
Deposited On:22 Nov 2017 17:16
Last Modified:15 Nov 2021 19:58

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