Optical and electrochemical effects of H₂ and O₂ bubbles at upward-facing Si photoelectrodes
Abstract
The effects of the size, contact-angle, and coverage of gas bubbles on solar fuels devices were characterized at cm-scale, upward-facing planar and microwire-array Si photoelectrodes in stagnant electrolytes. Experimental measurements were supported by ray-tracing simulations of surface attached gas bubble films. A dilute, redox-active tracer allowed for the quantification of the mass-transport effects of bubble coverage during photoanodic O₂ (g) evolution at upward-facing photoanodes in 1.0 M KOH(aq.). Measurements of the gas coverage at upward-facing p-Si photocathodes in 0.50 M H₂SO₄ (aq.) allowed for the nucleation rate and contact angle of H₂ (g) bubbles to be evaluated for systems having various surface free energies. Under simulated solar illumination, the rapid departure of small O₂ (g) bubbles produced stable photocurrents at upward-facing oxygen-evolving Si photoanodes and yielded increased mass-transport velocities relative to a stagnant electrolyte, indicating that bubbles can provide a net benefit to the photoelectrochemical performance of an upward-facing photoanode in solar fuels devices.
Additional Information
© 2020 The Royal Society of Chemistry. Submitted 31 Aug 2020; Accepted 12 Nov 2020; First published 12 Nov 2020. 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. Silicon microwire arrays were fabricated in the Kavli Nanoscience Institute (KNI) at Caltech; we thank the KNI staff for their assistance with fabrication. We are grateful to Rick Gerhart for assistance in fabricating glassware for solar simulations. Additional instrumentation was provided by the Molecular Materials Research Center in the Beckman Institute at Caltech. We appreciate Bruce Brunschwig for providing helpful feedback on the manuscript. Author contributions: Si-μW Fabrication, P. A. K., Metallization, Z. P. I., Atomic Layer Deposition, W. Y., Scanning-Electron Microscopy, A. I. C., Investigation, P. A. K.; Writing – Original Draft, P. A. K. and N. S. L., Writing – Review and Editing, P. A. K., N. S. L., Z. P. I., W. Y., A. I. C., Funding Acquisition, N. S. L. Supervision, N. S. L. The authors declare no competing interests.Attached Files
Supplemental Material - d0ee02796k1.pdf
Supplemental Material - d0ee02796k2.mp4
Supplemental Material - d0ee02796k3.mp4
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Additional details
- Alternative title
- Optical and electrochemical effects of H2 and O2 bubbles at upward-facing Si photoelectrodes
- Eprint ID
- 106813
- DOI
- 10.1039/d0ee02796k
- Resolver ID
- CaltechAUTHORS:20201124-121041867
- DE-SC0004993
- Department of Energy (DOE)
- Created
-
2020-11-24Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- JCAP, Kavli Nanoscience Institute