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Irreversible electrocatalytic reduction of V(V) to V(IV) using phosphomolybdic acid

Freund, Michael S. and Lewis, Nathan S. (1994) Irreversible electrocatalytic reduction of V(V) to V(IV) using phosphomolybdic acid. Inorganic Chemistry, 33 (8). pp. 1638-1643. ISSN 0020-1669. https://resolver.caltech.edu/CaltechAUTHORS:20180529-141900848

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Abstract

Although VO_22^+(aq) reduction is kinetically slow at glassy carbon and Pt electrodes, phosphomolybdic acid is shown to catalyze the electrochemical reduction of VO_2^+(aq) to VO_2^+(aq) in 1.0 M H_2SO_4(aq). A second-order rate constant of 33 M^(-1) s^(-1) was observed for this process. ^(31)P NMR spectra demonstrated that PMo_(11)VO_(40)^(4-) and PMo_(18)V_2O_(40)^(50-) were the dominant P-containing species under electrocatalytic conditions. The incorporation of V^V into the polyoxoanion led to a shift in potential from E^o(VO^(2+)(aq)/VO^(2+)(aq)) = +0.80 V vs Ag/AgCl for free V^V/V^(IV) to Eo' = +0.55 V vs Ag/AgCl for V^(V)/V^(Iv) bound in the heteropolyoxometalate (PMo_(11)VO_(40_^(4-)). This shift in formal potential corresponded to an equilibrium constant of 1.7 X 10^4 M^(-1) for preferential binding of V^V over V^(IV) by the heteropolyoxoanion. This negative shift in redox potential, combined with the slow electrochemical kinetics of free VO_2^+(aq) reduction and with the facile reaction of bound V^(IV) with free V^V in 1.0 M H_2SO_4(aq), resulted in the irreversible electrocatalytic reduction of VO_2^+(aq) to VO^(2+)(aq).


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/ic00086a013DOIArticle
ORCID:
AuthorORCID
Freund, Michael S.0000-0003-1104-2292
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 1994 American Chemical Society. Received January 28, 1993. We acknowledge ARPA for support of this work and thank Professors F. C. Anson and J. E. Bercaw and Dr. J. Labinger of Caltech for helpful discussions and Dr. D. A. Keire for help with ^(31)P NMR. We also acknowledge Dr. J. Grate for generously supplying a preprint of ref 3d.
Funders:
Funding AgencyGrant Number
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Division of Chemistry and Chemical Engineering8794
Issue or Number:8
Record Number:CaltechAUTHORS:20180529-141900848
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180529-141900848
Official Citation:Irreversible electrocatalytic reduction of V(V) to V(IV) using phosphomolybdic acid Michael S. Freund and Nathan S. Lewis Inorganic Chemistry 1994 33 (8), 1638-1643 DOI: 10.1021/ic00086a013
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86676
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:29 May 2018 21:40
Last Modified:03 Oct 2019 19:46

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