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Title: Energetic Tug-of-War between Pt and Leaky TiO 2 : Positive and Negative Effects on the Function of Molecularly-Modified p-Si(111)|TiO 2 |Pt Photocathodes

Abstract

Photoelectrochemical solar energy conversion to chemical products is a promising avenue towards renewable fuels, and TiO 2 deposition on semiconductor photocathodes is a widespread surface protection strategy. However, the electronic, thermodynamic, and kinetic effects of protection layers on interfacial energetics remains poorly understood. Here, electrochemical data (photocurrent onset and flatband potentials) of p-Si(111)|TiO 2|Pt is collected in contact with an outer-sphere redox couple. We find that onset potentials shift negatively as a function of increasing oxide thickness, but this effect is not reflected in the flatband potentials. This reveals the mechanism of these shifts is kinetic rather than thermodynamic,and suggests that hole leakage through the TiO 2 is responsible. When Pt nanoparticles are deposited onto the TiO 2, positive shifts in both the onset and flatband potentials are observed, revealing Pt catalysts are beneficial for more than just increased catalytic rates. These results highlight the importance of understanding the effects of surface modifications on the energetics at the interface in both catalytic and simple electron transfer systems.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [2]
  1. Univ. of Texas, Austin, TX (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Texas, Austin, TX (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1603925
Alternate Identifier(s):
OSTI ID: 1602096
Report Number(s):
[NREL/JA-5900-74948]
[Journal ID: ISSN 2196-0216]
Grant/Contract Number:  
[AC36-08GO28308]
Resource Type:
Accepted Manuscript
Journal Name:
ChemElectroChem
Additional Journal Information:
[ Journal Volume: 7; Journal Issue: 4]; Journal ID: ISSN 2196-0216
Publisher:
ChemPubSoc Europe
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; photoelectrochemistry; silicon; leaky TiO2; semiconductors; voltammetry; impedance

Citation Formats

Pekarek, Ryan T., Boucher, Dylan G., Neale, Nathan R., and Rose, Michael J. Energetic Tug-of-War between Pt and Leaky TiO2 : Positive and Negative Effects on the Function of Molecularly-Modified p-Si(111)|TiO 2 |Pt Photocathodes. United States: N. p., 2020. Web. doi:10.1002/celc.201901758.
Pekarek, Ryan T., Boucher, Dylan G., Neale, Nathan R., & Rose, Michael J. Energetic Tug-of-War between Pt and Leaky TiO2 : Positive and Negative Effects on the Function of Molecularly-Modified p-Si(111)|TiO 2 |Pt Photocathodes. United States. doi:10.1002/celc.201901758.
Pekarek, Ryan T., Boucher, Dylan G., Neale, Nathan R., and Rose, Michael J. Thu . "Energetic Tug-of-War between Pt and Leaky TiO2 : Positive and Negative Effects on the Function of Molecularly-Modified p-Si(111)|TiO 2 |Pt Photocathodes". United States. doi:10.1002/celc.201901758.
@article{osti_1603925,
title = {Energetic Tug-of-War between Pt and Leaky TiO2 : Positive and Negative Effects on the Function of Molecularly-Modified p-Si(111)|TiO 2 |Pt Photocathodes},
author = {Pekarek, Ryan T. and Boucher, Dylan G. and Neale, Nathan R. and Rose, Michael J.},
abstractNote = {Photoelectrochemical solar energy conversion to chemical products is a promising avenue towards renewable fuels, and TiO2 deposition on semiconductor photocathodes is a widespread surface protection strategy. However, the electronic, thermodynamic, and kinetic effects of protection layers on interfacial energetics remains poorly understood. Here, electrochemical data (photocurrent onset and flatband potentials) of p-Si(111)|TiO2|Pt is collected in contact with an outer-sphere redox couple. We find that onset potentials shift negatively as a function of increasing oxide thickness, but this effect is not reflected in the flatband potentials. This reveals the mechanism of these shifts is kinetic rather than thermodynamic,and suggests that hole leakage through the TiO2 is responsible. When Pt nanoparticles are deposited onto the TiO2, positive shifts in both the onset and flatband potentials are observed, revealing Pt catalysts are beneficial for more than just increased catalytic rates. These results highlight the importance of understanding the effects of surface modifications on the energetics at the interface in both catalytic and simple electron transfer systems.},
doi = {10.1002/celc.201901758},
journal = {ChemElectroChem},
number = [4],
volume = [7],
place = {United States},
year = {2020},
month = {2}
}

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