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Comparison of the Photoelectrochemical Behavior of H‑Terminated and Methyl-Terminated Si(111) Surfaces in Contact with a Series of One-Electron, Outer-Sphere Redox Couples in CH_3CN

Grimm, Ronald L. and Bierman, Matthew J. and O'Leary, Leslie E. and Strandwitz, Nicholas C. and Brunschwig, Bruce S. and Lewis, Nathan S. (2012) Comparison of the Photoelectrochemical Behavior of H‑Terminated and Methyl-Terminated Si(111) Surfaces in Contact with a Series of One-Electron, Outer-Sphere Redox Couples in CH_3CN. Journal of Physical Chemistry C, 116 (44). pp. 23569-23576. ISSN 1932-7447. doi:10.1021/jp308461q. https://resolver.caltech.edu/CaltechAUTHORS:20130128-141927544

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Abstract

The photoelectrochemical behavior of methyl-terminated p-type and n-type Si(111) surfaces was determined in contact with a series of one-electron, outer-sphere, redox couples that span >1 V in the Nernstian redox potential, E(A/A^−), of the solution. The dependence of the current vs potential data, as well as of the open-circuit photovoltage, V_(OC), on E(A/A^−) was compared to the behavior of H-terminated p-type and n-type Si(111) surfaces in contact with these same electrolytes. For a particular E(A/A^−) value, CH_3-terminated p-Si(111) electrodes showed lower V_(OC) values than Hterminated p-Si(111) electrodes, whereas CH_3-terminated n-Si(111) electrodes showed higher V_(OC) values than H-terminated n-Si(111) electrodes. Under 100 mW cm^(−2) of ELH-simulated Air Mass 1.5 illumination, n-type H−Si(111) and CH_3−Si(111) electrodes both demonstrated nonrectifying behavior with no photovoltage at very negative values of E(A/A^−) and produced limiting V_(OC) values of >0.5 V at very positive values of E(A/A^−). Illuminated p-type H−Si(111) and CH_3−Si(111) electrodes produced no photovoltage at positive values of E(A/A^−) and produced limiting V_(OC) values in excess of 0.5 V at very negative values of E(A/A^−). In contact with CH_3CN-octamethylferrocene^(+/0), differential capacitance vs potential experiments yielded a −0.40 V shift in flat-band potential for CH_3-terminated n-Si(111) surfaces relative to H-terminated n-Si(111) surfaces. Similarly, in contact with CH_3CN-1,1′-dicarbomethoxycobaltocene^(+/0), the differential capacitance vs potential data indicated a −0.25 V shift in the flat-band potential for CH_3-terminated p-Si(111) electrodes relative to H-terminated p-Si(111) electrodes. The observed trends in V_(OC) vs E(A/A^−), and the trends in the differential capacitance vs potential data are consistent with a negative shift in the interfacial dipole as a result of methylation of the Si(111) surface. The negative dipole shift is consistent with a body of theoretical and experimental comparisons of the behavior of CH_3−Si(111) surfaces vs H−Si(111) surfaces, including density functional theory of the sign and magnitude of the surface dipole, photoemission spectroscopy in ultrahigh vacuum, the electrical behavior of Hg/Si contacts, and the pH dependence of the current−potential behavior of Si electrodes in contact with aqueous electrolytes.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp308461qDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp308461qPublisherArticle
ORCID:
AuthorORCID
Grimm, Ronald L.0000-0003-0407-937X
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2012 American Chemical Society. Received: September 11, 2012; Revised: October 12, 2012; Published: October 13, 2012. We acknowledge the National Science Foundation (CHE-1214152 and CHE-0911682) and the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology for supporting this work. The authors thank Dr. David Knapp for his synthesis of 1,1′-dicarbomethoxycobaltocene^(+/0) as well as Dr. Chengxiang Xiang and Professor Erik Johansson for helpful discussions.
Funders:
Funding AgencyGrant Number
NSFCHE-1214152
NSFCHE-0911682
Caltech Beckman InstituteUNSPECIFIED
Subject Keywords:Electrochemistry
Issue or Number:44
DOI:10.1021/jp308461q
Record Number:CaltechAUTHORS:20130128-141927544
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130128-141927544
Official Citation:Comparison of the Photoelectrochemical Behavior of H-Terminated and Methyl-Terminated Si(111) Surfaces in Contact with a Series of One-Electron, Outer-Sphere Redox Couples in CH3CN Ronald L. Grimm, Matthew J. Bierman, Leslie E. O’Leary, Nicholas C. Strandwitz, Bruce S. Brunschwig, and Nathan S. Lewis The Journal of Physical Chemistry C 2012 116 (44), 23569-23576
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36630
Collection:CaltechAUTHORS
Deposited By: Aucoeur Ngo
Deposited On:08 Feb 2013 17:22
Last Modified:09 Nov 2021 23:23

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