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CoP as an Acid-Stable Active Electrocatalyst for the Hydrogen-Evolution Reaction: Electrochemical Synthesis, Interfacial Characterization and Performance Evaluation

Saadi, Fadl H. and Carim, Azhar I. and Verlage, Erik and Hemminger, John C. and Lewis, Nathan S. and Soriaga, Manuel P. (2014) CoP as an Acid-Stable Active Electrocatalyst for the Hydrogen-Evolution Reaction: Electrochemical Synthesis, Interfacial Characterization and Performance Evaluation. Journal of Physical Chemistry C, 118 (50). pp. 29294-29300. ISSN 1932-7447. http://resolver.caltech.edu/CaltechAUTHORS:20141020-091512216

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Abstract

Films of CoP have been electrochemically synthesized, characterized, and evaluated for performance as a catalyst for the hydrogen-evolution reaction (HER). The film was synthesized by cathodic deposition from a boric acid solution of Co^(2+) and H_2PO_2^– on copper substrates followed by operando remediation of exogenous contaminants. The films were characterized structurally and compositionally by scanning-electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman spectrophotometry. The catalytic activity was evaluated by cyclic voltammetry and chronopotentiometry. Surface characterization prior to electrocatalysis indicated that the film consisted of micrometer-sized spherical clusters located randomly and loosely on a slightly roughened surface. The composition of both the clusters and surface consisted of cobalt in the metallic, phosphide, and amorphous-oxide forms (CoO·Co_2O_3) and of phosphorus as phosphide and orthophosphate. The orthophosphate species, produced by air-oxidation, were eliminated upon HER electrocatalysis in sulfuric acid. The operando film purification yielded a functional electrocatalyst with a Co:P stoichiometric ratio of 1:1. After the HER, the surface was densely packed with micrometer-sized, mesa-like particles whose tops were flat and smooth. The CoP eletrodeposit exhibited an 85 mV overvoltage (η) for the HER at a current density of 10 mA cm^(–2) and was stable under operation in highly acidic solution, with an increase in η of 18 mV after 24 h of continuous operation. The comparative HER catalytic performance of CoP, film or nanoparticles, is as follows: η_(Pt) < η_(CoP film) = η_(CoP NP), η_(Ni_2P) < η_(CoSe)_2 < η_(MoS)_2 < η_(MoSe)_2.


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http://pubs.acs.org/doi/abs/10.1021/jp5054452PublisherArticle
http://dx.doi.org/10.1021/jp5054452DOIArticle
http://pubs.acs.org/doi/suppl/10.1021/jp5054452Related ItemSupporting Information
ORCID:
AuthorORCID
Saadi, Fadl H.0000-0003-3941-0464
Carim, Azhar I.0000-0003-3630-6872
Lewis, Nathan S.0000-0001-5245-0538
Soriaga, Manuel P.0000-0002-0077-6226
Additional Information:© 2014 American Chemical Society. Received: June 2, 2014. Revised: September 27, 2014. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. A.I.C. acknowledges a National Science Foundation Graduate Research Fellowship for support.
Group:JCAP
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
NSF Graduate Research FellowshipUNSPECIFIED
Record Number:CaltechAUTHORS:20141020-091512216
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141020-091512216
Official Citation:CoP as an Acid-Stable Active Electrocatalyst for the Hydrogen-Evolution Reaction: Electrochemical Synthesis, Interfacial Characterization and Performance Evaluation Fadl H. Saadi, Azhar I. Carim, Erik Verlage, John C. Hemminger, Nathan S. Lewis, and Manuel P. Soriaga The Journal of Physical Chemistry C 2014 118 (50), 29294-29300 DOI: 10.1021/jp5054452
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50531
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Oct 2014 18:40
Last Modified:12 Oct 2017 17:18

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