Enhanced Stability and Efficiency for Photoelectrochemical Iodide Oxidation by Methyl Termination and Electrochemical Pt Deposition of n-Si Microwire Arrays
Abstract
Arrays of Si microwires doped n-type (n-Si) and surface-functionalized with methyl groups have been used, with or without deposition of Pt electrocatalysts, to photoelectrochemically oxidize I–(aq) to I_3–(aq) in 7.6 M HI(aq). Under conditions of iodide oxidation, methyl-terminated n-Si microwire arrays exhibited stable short-circuit photocurrents over a time scale of days, albeit with low energy-conversion efficiencies. In contrast, electrochemical deposition of Pt onto methyl-terminated n-Si microwire arrays consistently yielded energy-conversion efficiencies of ∼2% for iodide oxidation, with an open-circuit photovoltage of ∼400 mV and a short-circuit photocurrent density of ∼10 mA cm^(–2) under 100 mW cm^(–2) of simulated air mass 1.5G solar illumination. Platinized electrodes were stable for >200 h of continuous operation, with no discernible loss of Si or Pt. Pt deposited using electron-beam evaporation also resulted in stable photoanodic operation of the methyl-terminated n-Si microwire arrays but yielded substantially lower photovoltages than when Pt was deposited electrochemically.
Additional Information
© 2019 American Chemical Society. Received: July 17, 2019; Accepted: July 24, 2019; Published: July 25, 2019. This work was supported by the National Science Foundation (NSF) Center for Chemical Innovation (CCI) Powering the Planet grants (Grants CHE-0802907, CHE-0947829, and NSF-ACCF) and made use of the Molecular Materials Resource Center of the Beckman Institute at Caltech and the Kavli Nanoscience Institute at Caltech. S.A. acknowledges support from a U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) Postdoctoral Research Award under the EERE Fuel Cell Technologies Program. The authors declare no competing financial interest.Attached Files
Supplemental Material - nz9b01529_si_001.pdf
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Additional details
- Eprint ID
- 97497
- Resolver ID
- CaltechAUTHORS:20190729-153032767
- NSF
- CHE-0802907
- NSF
- CHE-0947829
- Caltech Beckman Institute
- Kavli Nanoscience Institute
- Department of Energy (DOE)
- Created
-
2019-07-30Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Kavli Nanoscience Institute