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

Ronald L. Grimm, Matthew J. Bierman, Leslie E. O'Leary, Nicholas C. Strandwitz, Bruce S. Brunschwig, Nathan S Lewis

Research output: Contribution to journalArticle

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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 H-terminated 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.

Original languageEnglish
Pages (from-to)23569-23576
Number of pages8
JournalJournal of Physical Chemistry C
Volume116
Issue number44
DOIs
Publication statusPublished - Nov 8 2012

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methylidyne
Electrodes
electrodes
Electrons
electrons
photovoltages
Capacitance
capacitance
shift
dipoles
Electrolytes
electrolytes
trends
Oxidation-Reduction
methylation
Methylation
air masses
Ultrahigh vacuum
Photoelectron spectroscopy
ultrahigh vacuum

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

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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.; Bierman, Matthew J.; O'Leary, Leslie E.; Strandwitz, Nicholas C.; Brunschwig, Bruce S.; Lewis, Nathan S.

In: Journal of Physical Chemistry C, Vol. 116, No. 44, 08.11.2012, p. 23569-23576.

Research output: Contribution to journalArticle

Grimm, Ronald L. ; Bierman, Matthew J. ; O'Leary, Leslie E. ; Strandwitz, Nicholas C. ; Brunschwig, Bruce S. ; Lewis, Nathan S. / 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. In: Journal of Physical Chemistry C. 2012 ; Vol. 116, No. 44. pp. 23569-23576.
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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 H-terminated 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.",
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T1 - 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

AU - Grimm, Ronald L.

AU - Bierman, Matthew J.

AU - O'Leary, Leslie E.

AU - Strandwitz, Nicholas C.

AU - Brunschwig, Bruce S.

AU - Lewis, Nathan S

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N2 - 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 H-terminated 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.

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